barbarahealth

When a prostate-specific antigen (PSA) blood test produces an abnormal result, the next step is usually a prostate biopsy. A biopsy can confirm or rule out a cancer diagnosis, but it also has certain drawbacks. Prostate biopsies are invasive procedures with potential side effects, and they often detect low-grade, slow-growing tumors that may not need immediate treatment — or any treatment at all.

Researchers are exploring various strategies for avoiding unnecessary biopsies. Specialized magnetic resonance imaging (MRI) scans, for instance, can be useful for predicting if a man’s tumor is likely to spread. A blood test called the Prostate Health Index (PHI) measures various forms of PSA, and can help doctors determine if a biopsy is needed.

In April, researchers at the University of Michigan published results with a test that screens for prostate cancer in urine samples. Called the MyProstateScore 2.0 (MPS2) test, it looks for 18 different genes associated with high-grade tumors. “If you’re negative on this test, it’s almost certain that you don’t have aggressive prostate cancer,” said Dr. Arul Chinnaiyan, a professor of pathology and urology at the University, in a press release.

Gathering data and further testing

To create the test, Dr. Chinnaiyan and his colleagues first turned to publicly-available databases containing over 58,000 prostate cancer-associated genes. From that initial pool, they narrowed down to 54 genes that are uniquely overexpressed in cancers classified as Grade Group 2 (GG2) or higher. The Grade Group system ranks prostate cancers from GG1 (the least dangerous) to GG5 (the most dangerous).

The team tested those 54 genes against archived urine samples from 761 men with elevated PSA who were scheduled for biopsy. This effort yielded 18 genes that consistently correlated with high-grade cancer in the biopsy specimens. These genes now make up MPS2.

Then the team validated the test by performing MPS2 testing on over 800 archived urine samples collected by a national prostate cancer research consortium. Other researchers affiliated with that consortium assessed the new urine test’s results against patient records.

Interpreting the results

Study findings showed that MPS2 correctly identified 95% of the GG2 prostate cancers and 99% of cancers that were GG3 or higher. Test accuracy was further improved by incorporating estimates of the prostate’s size (or volume, as it’s also called).

According to the team’s calculations, use of the MPS2 would have reduced unnecessary biopsies by 37%. If volume was included in the measure, then 41% of biopsies would have been avoided. By comparison, just 26% of biopsies would have been avoided with the PHI.

Dr. Chinnaiyan and his co-authors emphasize that ruling out high-grade cancer with a urine test offers some advantages over MRI. The specialized multi-parametric MRI scans needed to assess high-grade cancer in men with elevated PSA aren’t always available in community settings, for instance. Moreover, the interpretation of mpMRI results can vary from one radiologist to another. Importantly, the MPS2 can be updated over time as new prostate-cancer genes are identified.

Commentary

Dr. Boris Gershman, a urologist at Harvard-affiliated Beth Israel Deaconess Medical Center in Boston, and a member of the advisory and editorial board for the Harvard Medical School Guide to Prostate Diseases, described the new study results as promising. “It does appear that the performance of the 18-gene urine test is better than PSA alone,” he says.

But Dr. Gershman adds that it will be important to consider how such a test will fit into the current two-stage approach for PSA screening, which entails prostate MRI when the PSA is abnormal. Where MRI delivers a yes/no result (meaning lesions that look suspicious for cancer are either present or not), the MPS2 provides numerical risk estimates ranging between 0% and 100%. “The challenge with clinical implementation of a continuous risk score is where to draw the line for biopsy,” Dr. Gershman says.

“This research is very encouraging, since many men in rural areas may not have access to prostate MRI machines or the added sophistication that is needed in interpreting these MRI scans,” says Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center. “A widely available urine test may eventually help provide more precision in determining who should undergo a prostate biopsy, and may also help to assess the probability that a cancer is clinically significant and in need of treatment.”

About the Author

Charlie Schmidt, Editor, Harvard Medical School Annual Report on Prostate Diseases

Charlie Schmidt is an award-winning freelance science writer based in Portland, Maine. In addition to writing for Harvard Health Publishing, Charlie has written for Science magazine, the Journal of the National Cancer Institute, Environmental Health Perspectives, … See Full Bio View all posts by Charlie Schmidt

About the Reviewer

Marc B. Garnick, MD, Editor in Chief, Harvard Medical School Annual Report on Prostate Diseases; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Marc B. Garnick is an internationally renowned expert in medical oncology and urologic cancer. A clinical professor of medicine at Harvard Medical School, he also maintains an active clinical practice at Beth Israel Deaconess Medical … See Full Bio View all posts by Marc B. Garnick, MD

If you are trying to cut back on added sugar — and you should, because excess sugar increases risks for obesity, diabetes, and heart disease — you might be tempted by products advertised as low sugar, no sugar, or sugar-free.

Many contain familiar low-calorie sugar substitutes like aspartame or sucralose instead of sugar. And as you’re reading labels, you also may run across another ingredient: sugar alcohol, which is used in products like sugar-free cookies, candies, ice cream, beverages, and chewing gums. Are any of these sweeteners a better choice nutritionally? Dr. Frank Hu, professor of nutrition and epidemiology with the Harvard T.H. Chan School of Public Health, weighs in below.

Are low-calorie or no-calorie sweeteners any healthier than natural sugar?

Also known as artificial sweeteners or sugar substitutes, the list of low-calorie and no-calorie sweeteners you may see on product nutrition labels includes acesulfame-K, saccharin, sucralose, neotame, and advantame. These have a higher sweetness intensity per gram than natural sugar.

So far research on them is mixed, although some observational studies have found that beverages containing low-calorie sweeteners are associated with a higher risk for diabetes and weight gain.

What exactly are sugar alcohols and how can you spot them?

Sugar alcohols may have the most misleading name, as they are neither sugar nor alcohol, according to Dr. Hu. “They are a type of carbohydrate derived from fruits and vegetables, although most commercial sugar alcohols are synthetically produced.”

You can usually spot many sugar alcohols on ingredient lists by “-ol” at the ends of their names. Examples include sorbitol, xylitol, lactitol, mannitol, erythritol, and maltitol.

Are sugar alcohols any healthier than other sugar substitutes or natural sugar?

Here is a look at the pros and cons.

The upside of sugar alcohols

Sugar alcohols reside in the sweet spot between natural sugar and low-calorie sweeteners. They are not as overly sweet as sweeteners and don’t add too many extra calories like sugar.

“Sugar alcohols are about 40% to 80% as sweet as natural sugar, whereas artificial sweeteners like aspartame are about 200 times sweeter,” says Dr. Hu. “And they have about 25% to 75% fewer calories per gram than sugar.”

Another upside of sugar alcohols is that they break down slowly in the gut. Hence, your body only absorbs part of their overall carbohydrates. “This keeps your blood sugar and insulin levels from spiking as they do with sugar,” says Dr. Hu. “That makes them a useful sugar substitute for people with diabetes.”

The downside of sugar alcohols

The main downside to sugar alcohols is this: when taken in high amounts they can cause gastrointestinal (GI) problems, such as abdominal pain, diarrhea, or loose stools.

Because sugar alcohols are slowly digested, they have more time to feed bacteria in the gut, which can lead to fermentation and produce excess gas. Their slow digestion also can pull extra water into the colon and cause a laxative effect.

People’s tolerance for sugar alcohols depends on many factors, including body weight, health conditions, and the amount and types of sugar alcohols. “Individual differences in digestion and metabolism, gut microbiome composition, and dietary habits can also make a difference,” says Dr. Hu. “For these reasons, we recommend introducing sugar alcohols into your diet gradually and observing how your body responds.”

For people who experience GI symptoms caused by sugar alcohols, Dr. Hu says cutting back on the amount of foods and drinks made with them often can correct the problem. “Sugar alcohols are commonly found in sugar-free or low-carb products, so pay attention to food labels” he says. “Because different sugar alcohols can have different effects, it might be useful to identify specific types of sugar alcohols that cause GI side effects.”

Do sugar alcohols have health risks?

Possible long-term health risks of sugar alcohol are still being explored. A 2023 observational study found a link between using erythritol as an added sweetener and cardiovascular disease events, such as stroke and heart attack, in people with heart disease or who had risk factors like diabetes and high blood pressure. However, these findings have not been confirmed in subsequent studies.

“Sugar alcohols offer a healthier alternative to sugar because of their lower calorie content and reduced glycemic response, which is the effect food has on blood sugar levels,” says Dr. Hu. “But they also have potential drawbacks, especially for those with sensitive digestive systems, so it’s best to consume them in moderation as part of an overall healthy eating pattern.”

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

It’s never easy for parents to talk to their teens about having sex. Many parents feel that talking about it is the same as condoning it, so they are hesitant to do so. But according to the most recent Youth Risk Behavior Survey (YRBS), a national survey of high school students, by the end of high school 30% have had sex.

It can be impossible to know for sure if your teen has had sex. Even if they haven’t, it’s likely that at some point they will — and they need to have information to help keep themselves safe and healthy.

What parents should know about sexually transmitted infections

Sexually transmitted infections, or STIs, are very common. They may be caused by bacteria, viruses, or other microorganisms, and spread through all kinds of sex. While most STIs are treatable, they can affect fertility in both women and men, can cause health problems for a baby during pregnancy, and can sometimes lead to lifelong infection or serious complications. That’s why teens need to know about them.

Below are the high-level facts about some of the most common infections: what causes them, what symptoms may occur, and how they are treated.

Chlamydia

Chlamydia is the most frequently reported bacterial STI in the United States — but just as many cases are asymptomatic, so the numbers may be higher than we realize.

Symptoms, if they are present, can include discharge from the vagina or penis, pain with urination, or pain and swelling of the testicles (this is rare). A test of the urine (or a swab from the affected area) can diagnose it, and it is curable with antibiotics. If left untreated it can lead to infertility, more commonly in women than men.

Gonorrhea

Gonorrhea is another STI caused by a bacteria, and it can also be asymptomatic. When symptoms occur, they are very similar to chlamydia. Gonorrhea also can cause infertility in both women and men. While it is treatable, some infections have been resistant to the usual antibiotics used, so additional testing and treatment is sometimes needed.

Trichomoniasis

Trichomoniasis is caused by a protozoa. It is another STI that can be asymptomatic. When there are symptoms, they are usually itch, irritation, and discharge. It is curable with medication.

Syphilis

Syphilis has been on the rise. In the first stage of infection there is usually a firm, round, painless sore where the infection entered the body. The sore is generally there for three to six weeks, but as it is painless it may go unnoticed.

In the second stage there is a more extensive rash, though it can be faint and go unnoticed, along with general feelings of illness such as fever, sore throat, fatigue, swollen lymph nodes, or weight loss.

If syphilis still goes unnoticed it can linger in the body for years, sometimes affecting organ systems, including the brain. It is curable with antibiotics, but if found late the damage it can do may be permanent. This infection can be very serious during pregnancy.

HSV

HSV (herpes simplex virus) causes blistering sores. There is both oral herpes (mouth sores) and genital herpes. Oral herpes, caused by HSV1, is not usually caused by sex — but it can lead to genital herpes through oral sex. Genital herpes is more commonly caused by HSV2.

The sores of herpes can recur throughout life. There is no cure for herpes, but there are medications that can shorten or prevent outbreaks. This infection can be particularly dangerous during pregnancy, although the risks can be managed with good prenatal care.

HPV

HPV (human papilloma virus) is the most common sexually transmitted infection. It can be transmitted even by close skin-to-skin touch, and infections are generally asymptomatic.

Most cases of HPV (90%) get better by themselves — but if they don’t, over time the virus can cause genital warts or certain cancers. Luckily, there is an effective vaccine to prevent HPV that can be given starting at age 9.

HIV

HIV (human immunodeficiency virus) is more common among people who have other STIs — mostly because having STIs is a sign of risky sexual behavior. It can be very hard to know if a person has it, because the early symptoms can feel like having the flu, and then people can move into a long period of time of having no symptoms at all.

While there is no cure for HIV, there are medications to control it, as well as medications that can prevent it.

Talking to teens about preventing STIs

All of this sounds scary. But there are actually some simple things teens can do to prevent infections or minimize complications, which is why parents need to talk with them.

Teens can:

• Use condoms every single time they have sex — and use them properly. According to the report mentioned above, about half of sexually active high schoolers don’t use condoms regularly.
• Limit their number of sexual partners — and have frank conversations with those partners before having sex. Asking about sexual history, and getting testing before starting a sexual relationship, can make a difference.
• Get tested regularly. Sexually active teens should be tested for gonorrhea and chlamydia every year, or more frequently based on their sexual history or symptoms. Testing for other infections may be a good idea too. In the YRBS, 95% of high schoolers had not been tested for STIs in the past year, which is frightening given that nearly a third report being sexually active.

Make sure your teen sees their doctor regularly. And encourage them to be honest with their doctor during their visits. As a parent, you can help by giving your teen confidential time alone with the doctor.

About the Author

Claire McCarthy, MD, Senior Faculty Editor, Harvard Health Publishing

Claire McCarthy, MD, is a primary care pediatrician at Boston Children’s Hospital, and an assistant professor of pediatrics at Harvard Medical School. In addition to being a senior faculty editor for Harvard Health Publishing, Dr. McCarthy … See Full Bio View all posts by Claire McCarthy, MD

Here’s a new fact about spring, summer, fall, and sometimes even winter: now that climate change has blurred seasonal boundaries, sizzling heat may be on the way, or currently blanketing your community.

High temperatures stress the body, leading to thousands of heat-related illnesses and deaths every year in the US. Creating a personal heat plan can help you stay safe when the heat index soars.

Caleb Dresser, MD, MPH, is the health care solutions lead for C-CHANGE, the Center for Climate Health and the Global Environment at the Harvard T.H. Chan School of Public Health, and an emergency medicine doctor at Harvard-affiliated Beth Israel Deaconess Medical Center. Below we interview him about who, how, and why heat harms. Then we’ll help you create your personal heat safety plan.

Interview edited for clarity

Who is especially vulnerable during hot weather?

High temperatures can affect anyone. But some people — children, outdoor workers, people who are pregnant or have health problems or disabilities, and older people — are more likely to experience harm when temperatures rise. For example:

• Young children, especially babies, have less physical capacity to deal with very high temperatures.
• People working outdoors may not have access to shade and could be performing physically intensive labor. They need adequate hydration, adequate breaks, and access to a cool space during break time, as OSHA guidelines spell out.
• People with chronic medical conditions, such as kidney disease or heart disease, may have difficulty adapting physiologically to hot weather, or may be more susceptible to its health impacts.
• And some people living with disabilities or certain neurological conditions may have difficulty with thermoregulation — that is, controlling the temperature of their bodies — or may not be able to take actions that keep them safe, such as taking off layers or moving to a cool area.

Which weather patterns create dangerous levels of heat?

Dangerous heat is the result of both high temperatures and high humidity, which interfere with our ability to cool off by sweating. In dry areas, extremely hot temperatures can be dangerous on their own.

Danger zones vary across the United States and around the world. But hospital use and deaths rise once we get above threshold temperatures. The threshold varies in different places depending on whether bodies, cultures, and architecture are adapted to heat.

For example, here in New England, where some people (particularly those of limited means) may not have access to air conditioning, we see increases in healthcare use and deaths at a lower temperature than in the American South, where people and organizations may be more used to dealing with hot weather.

When does hot weather become dangerous to our health?

Risk goes up the longer hot weather sticks around.

One hot day can put some people at risk. A stretch of several hot days in a row during a heat wave is particularly dangerous because it can overwhelm people’s ability to adapt. Eventually people run out of physiological reserves, leading to greater health harms and greater need for medical care.

Surprisingly, spring and early summer are particularly dangerous times because people and organizations aren’t as prepared for hot weather.

How to create your personal heat safety plan

Five key points to help you create a personal heat plan are below. Americares offers further information through heat tip sheets developed with the Harvard C-CHANGE team that are tailored to people in different health circumstances.

Planning is important because intense heat is occurring more often: a Climate Central analysis found 21 additional risky heat days, on average, for 232 out of 249 locations between 1970 and 2022.

• Stay ahead of hot weather. Check apps, websites, TV, or radio for updates on weather today and in coming days. If local weather alerts are available by phone or text, sign up.
• Have a cooling plan. When temperatures soar, you need to spend as much time as possible in cool spaces. Plan options if your home is likely to be too hot and unsafe to stay in. You may be able to stay with a neighbor or family member who has air conditioning until a heat wave passes. Many cities and towns have neighborhood splash pads for children, and open cooling centers or air-conditioned libraries, public buildings, or community centers to everyone — sometimes even overnight. Spending time in air-conditioned businesses or malls, or in a shady green space like a park, may help too.
• Sip plenty of fluids. Water is the best choice. Skip sugary drinks and avoid caffeine or alcohol.
• Use fans correctly. Fans help if surrounding air is relatively cool. If air temperatures are very high, it’s important to dampen your clothes or skin to help keep your body from overheating, and move to a cooler location, if possible.
• Know your personal risks and the signs of heat-related illness. If you have health problems or disabilities, or take certain medicines such as diuretics, talk to your doctor about the best ways for you to cope with heat. It’s also essential to know the signs of heat-related illnesses, which range from heat rash and sunburn to heat cramps, heat exhaustion, and heat stroke. This chart from the Centers for Disease Control and Prevention describes the signs to look for and what you can do, particularly when heat becomes an emergency.

About the Author

Francesca Coltrera, Editor, Harvard Health Blog

Francesca Coltrera is editor of the Harvard Health Blog, and a senior content writer and editor for Harvard Health Publishing. She is an award-winning medical writer and co-author of Living Through Breast Cancer and The Breast … See Full Bio View all posts by Francesca Coltrera

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

An F may mean failure in school, but the letter earns high marks in your diet. The two biggest dietary Fs — fiber and fermented foods — are top priorities to help maintain healthy digestion, and they potentially offer much more. How can you fit these nutrients into meals? Can this help your overall health as well as gut health?

Fiber, fermented foods, and the gut microbiome

The gut microbiome is a composed of bacteria, viruses, fungi, and other microorganisms living in the colon (large intestine). What you eat, the air you breathe, where you live, and many other factors affect the makeup of the gut microbiome. Some experts think of it as a hidden organ because it has a role in many important functions of the body — for example, helping the immune system function optimally, reducing chronic inflammation, keeping intestinal cells healthy, and providing some essential micronutrients that may not be included in a regular diet.

Your gut communicates with your brain through pathways in the gut-brain axis. Changes in the gut microbiome have been linked with mood and mental health disorders, such as depression and anxiety. However, it’s not yet clear that these changes directly cause these types of problems.

We do know that a healthy diet low in processed foods is key to a healthy gut microbiome. And increasing evidence suggests that fiber and fermented foods can play important parts here.

Fiber 101

Fiber’s main job is to make digestion smoother by softening and adding bulk to stool, making it pass quickly through the intestines.

But fiber has other benefits for your microbiome and overall health. A high-fiber diet helps keep body weight under control and lowers LDL (bad) cholesterol levels. Research has found that eating enough fiber reduces the risk of heart disease, type 2 diabetes, and some cancers.

What to know about fiber

There are two types of fiber: insoluble (which helps you feel full and encourages regular bowel movements) and soluble (which helps lower cholesterol and blood sugar). However, recent research suggests people should focus on the total amount of fiber in their diet, rather than type of fiber.

If you’re trying to add more foods with fiber to your diet, make sure you ease into new fiber-rich habits and drink plenty of water. Your digestive system must adapt slowly to avoid gas, bloating, diarrhea, and stomach cramps caused by eating too much too soon. Your body will gradually adjust to increasing fiber after a week or so.

How much fiber do you need?

The fiber formula is 14 grams for every 1,000 calories consumed. Your specific calorie intake can vary depending on your activity levels.

“But instead of tracking daily fiber, focus on adding more servings of fiber-rich foods to your diet,” says Eric Rimm, professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health.

Which foods are high in fiber?

Fruits, vegetables, legumes, nuts, seeds, and whole grains are all high in fiber. The Dietary Guidelines for Americans has a comprehensive list of fiber-rich foods and their calorie counts.

What about over-the-counter fiber supplements that come in capsules, powders that you mix with water, and chewable tablets? “If you have trouble eating enough fiber-rich foods, then these occasionally can be used, and there is no evidence they are harmful,” says Rimm. “But they should not serve as your primary source of dietary fiber.”

Fermented foods 101

Fermented foods contain both prebiotics — ingredients that create healthy changes in the microbiome — and beneficial live bacteria called probiotics. Both prebiotics and probiotics help maintain a healthy gut microbiome.

What to know about fermented foods

Besides helping with digestion and absorbing vital nutrients from food, a healthy gut supports your immune system to help fight infections and protect against inflammation. Some research suggests that certain probiotics help relieve symptoms of gut-related conditions like inflammatory bowel disease and irritable bowel syndrome, though not all experts agree with this.

Many foods that are fermented undergo lacto-fermentation, in which natural bacteria feed on the sugar and starch in the food, creating lactic acid. Not only does this process remove simple sugars, it creates various species of good bacteria, such as Lactobacillus or Bifidobacterium. (Keep in mind that some foods undergo steps that remove probiotics and other healthful microbes, as with beer or wine, or make them inactive, like baking and canning.)

The exact amounts and specific strains of bacteria in fermented foods vary depending on how they are made. In addition to probiotics, fermented foods may contain other valuable nutrients like enzymes, B vitamins, and omega-3 fatty acids.

How often should you eat fermented foods?

There is no recommended daily allowance for prebiotics or probiotics, so it is impossible to know precisely which fermented foods or quantities are best. The general guideline is to add more to your daily diet.

Which fermented foods should you choose?

Fermented foods have a range of tastes and textures because of the particular bacteria they produce during fermentation or that are added to foods. Yogurt is one of the most popular fermented foods (look for the words “live and active cultures” on the label). Still, many options are available if you are not a yogurt fan or want to expand your fermented choices. Kimchi, sauerkraut, kombucha, and pickles are a few examples.

As with fiber, probiotics are also marketed as over-the-counter supplements. However, like all dietary supplements, they do not require FDA approval, so there is no guarantee that the types of bacteria listed on a label can provide the promised benefits — or are even in the bottle. “Therefore, it is best to get your probiotics from fermented foods,” says Rimm.

To learn more about the value of fiber, fermented foods, and a healthy gut microbiome, listen to this episode of the Food, We Need to Talk podcast, “Understanding the Microbiome.”

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

A bird flu strain that began circulating in 2020 continues to evolve globally and locally within the United States. If you’re wondering what this means, understanding the basics — what bird flu is, how it spreads, whether foods are safe, and prevention tips — can help. More information will come in as scientists learn more, so stay tuned.

1. What is bird flu and how does it spread?

Bird flu, or avian flu, is a naturally occurring illness. Just as certain flu viruses spread among humans, Type A influenza viruses often spread among wild birds. The strain of virus circulating now is H5N1, named for two proteins on its surface.

Avian flu infections are highly contagious. Infection often spreads first among wild water birds, such as ducks, geese, and gulls, and shore birds, such as plovers and sandpipers. The viruses are carried in their intestines and respiratory tract and shed in saliva, mucus, and feces. Wild birds can easily infect domestic poultry, such as chickens, turkeys, and ducks.

Some bird species, including ducks, may carry and spread infection without appearing sick. Domestic flocks are more likely to sicken and possibly die from bird flus. However, not all avian flu viruses are equally harmful:

• Low pathogenic avian influenza (LPAI) may cause no signs of illness, or signs of mild illness like fewer eggs or ruffled feathers in domestic poultry.
• Highly pathogenic avian influenza (HPAI) causes more severe illness and high rates of death in infected poultry. The current H5N1 virus is considered an HPAI.

2. Can humans get bird flu?

Yes, though this doesn’t usually happen.

When flu viruses mutate, they may be able to move from their original hosts — birds in this case — to humans and other animals. As of early April 2024, only two cases of bird flu in humans had been reported in the US since 2022. In May, two more cases were reported. Newer case numbers of bird flu will continue to be reported by the CDC, which offers weekly snapshots of influenza in the US.

The virus may be introduced into the body through the eyes, nose, or mouth. For example, a person may inhale viral particles in the air (droplets, tiny aerosolized particles, or possibly in dust). Or they might touch a surface contaminated by the virus, then touch their eyes or nose. Bird flu in humans typically causes symptoms similar to seasonal flu, such as fever, runny nose, and body aches.

3. Which animals have been affected by bird flu?

A surprisingly long list of animals affected by the current H5NI bird flu infection includes:

• wild birds, chickens, ducks, geese, and other domestic and commercial poultry in 48 states and more than 500 countries
• livestock, such as dairy cows in nine states at this writing, and other farm animals
• marine animals, such as seals, sea lions, and even dolphins
• wild animals, such as foxes, skunks, and racoons, and some domestic animals, such as farm cats.

4. Why are experts concerned about this bird flu outbreak?

It might seem odd that there’s been so much concern and news coverage about bird flu lately. After all, bird flu has been around for many years. We’ve long known it sometimes infects nonbird animal species, including humans.

But the current outbreak is unique and worrisome for several reasons:

• Fast, far-reaching spread. The virus has been found throughout the US, Europe, the Middle East, Southeast Asia, multiple sub-Saharan African countries, and even Antarctica.
• Many species have been infected. Previously uninfected species have been affected, including animals in our food supply.
• Economic impact. If large numbers of beef and dairy cows and chickens sicken or must be culled (killed) to contain outbreaks, this could have a major economic impact on farmers, agriculture businesses, and affected countries’ economies. This could also mean higher prices at the grocery store.
• Opportunities for exposure. Though only two human infections were reported in the US in recent years — both in people working with animals — the more exposure humans have to bird flu, the more chances the virus has to develop mutations that allow easier spread to humans.
• Potential for fatalities. Severe strains of bird flu have led to H5N1 infections in nearly 900 people in 23 countries since 2003. More than half of these reported cases were fatal. Keep in mind that the math isn’t straightforward. It’s likely that many more cases of bird flu in humans occurred, yet people experiencing few or no symptoms or those not tested weren’t counted, so lethality is likely overestimated.
• New mutations. It’s rare, but possible: If this H5N1 bird flu develops mutations that enable efficient person-to-person spread, bird flu could become the next human pandemic.

5. Are milk, beef, chicken, and the rest of our food supply safe?

Public health officials emphasize that the food supply is safe.

But concern has understandably run high since the discovery that this outbreak has spread from birds to dairy cows for the first time. More alarming? A study found fragments of bird flu DNA — which is not the same as live virus — in 20% of commercially available milk in the US.

So far, there’s been no indication that bird flu found in pasteurized milk, beef, or other common foods can cause human illness. Even if live bird flu virus got into the milk supply, studies show that routine pasteurization would kill it. Initial tests did not find the virus in ground beef.

Of course, if you are particularly concerned, you could avoid foods and beverages that come from animals affected by bird flu. For example, you could switch to oat milk or almond milk, even though there’s no convincing scientific justification to do so now.

6. What if you have pets or work with animals?

Bird flu rarely spreads to pets. While that’s good news, your pets could have exposure to animals infected with bird flu, such as through eating or playing with a dead bird. So, it’s safest to limit your pet’s opportunities to interact with potentially infected animals.

If you work with animals, especially birds or livestock, or hunt, the Centers for Disease Control and Prevention (CDC) recommends precautions to minimize your exposure to bird flu.

7. What else can you do to stay safe?

The CDC recommends everyone take steps to avoid exposure to bird flu, including:

• Avoid contact with sick or dead animals and keep pets away from them.
• Avoid animal feces that may be contaminated by birds or bird droppings, as might be common on a farm.
• Do not prepare or eat raw or undercooked food.
• Do not drink raw (unpasteurized) milk or eat raw milk cheese or raw or undercooked foods from animals suspected of having bird flu infection.
• Wear personal protective equipment (PPE), such as safety goggles, gloves, and an N95 face mask, when working near sick or dead animals or their feces.

Right now, available evidence doesn’t support more dramatic preventive measures, such as switching to an all-plant diet.

8. Is there any good news about bird flu?

Despite all the worrisome news about bird flu, this recent outbreak may wind up posing little threat to human health. Virus strains may mutate to spread less efficiently or to be less deadly. Efforts are underway to contain the spread of bird flu to humans, including removing sick or exposed animals from the food supply and increased testing of dairy cattle before transport across state lines.

And there is other encouraging news:

• Some birds appear to be developing immunity to the virus. This could reduce the chances of continued spread between birds and other animals.
• Developing a vaccine to protect cattle from bird flu may be possible (though it’s unclear if this approach will be successful).
• If spread to humans does occur, genetic tests suggest available antiviral medicines could help treat people.
• So far, human-to-human transmission has not been detected. That makes it less likely that the H5N1 bird flu will become the next pandemic.
• And if human infections with bird flu did become more common, researchers are working on human vaccines against bird flu using virus strains that match well with those causing the current outbreak.

9. How worried should you be about bird flu?

Though there’s much we don’t know, this much seems certain: bird flu will continue to change and pose challenges for farmers and health experts to stay ahead of it. So far, public health experts believe that bird flu poses little health risk to the general public.

So, it’s not time to panic about bird flu. But it is a good idea to take common sense steps to avoid exposure and stay current on related news.

For updated information in the US, check the CDC website .

About the Authors

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

Francesca Coltrera, Editor, Harvard Health Blog

Francesca Coltrera is editor of the Harvard Health Blog, and a senior content writer and editor for Harvard Health Publishing. She is an award-winning medical writer and co-author of Living Through Breast Cancer and The Breast … See Full Bio View all posts by Francesca Coltrera

About the Reviewer

John Ross, MD, FIDSA, Contributor; Editorial Advisory Board Member, Harvard Health Publishing

Dr. John Ross is an assistant professor of medicine at Harvard Medical School. He is board certified in internal medicine and infectious diseases, and practices hospital medicine at Brigham and Women’s Hospital. He is the author … See Full Bio View all posts by John Ross, MD, FIDSA

In parts of the United States and Canada, warming temperatures driven by climate change may be contributing to a rise in tick-borne illnesses. Ticks are now thriving in a wider geographic range, and appearing earlier and sticking around later in the shoulder seasons of spring and fall. That means we need to stay vigilant about protecting ourselves against ticks that cause Lyme disease and other illnesses — even during winter months in many warmer states and provinces.

Here’s a timely reminder about why preventing Lyme disease is important, and a refresher on steps you can take to avoid tick bites.

What are the symptoms of Lyme disease?

Lyme disease is best known for its classic symptom, a bull’s-eye red rash that appears after a bite from an infected tick (scroll down to see photos of classic and non-classic rashes). However, 20% to 30% of people do not develop a rash. And a rash can be easy to miss because ticks tend to bite in dark body folds such as the groin, armpit, behind the ears, or on the scalp. Some people have flulike symptoms such as a headache, fever, chills, fatigue, and aching joints. So if you notice a rash or have these symptoms, call your doctor for advice. At this stage, prompt antibiotic treatment can wipe out the bacterial infection.

When people don’t receive treatment because they didn’t see the rash or didn’t have other early symptoms, the bacteria can spread to different parts of the body. Not only can the bacteria itself cause problems, but the body’s immune system can over-respond to the infection. Either process, or sometimes both, may harm joints, the heart, and/or the nervous system. And some people treated for any stage of Lyme disease develop post-Lyme disease syndrome, which can cause a range of debilitating symptoms that include fatigue, brain fog, and depression.

How to avoid getting Lyme disease

Preventing tick bites is the best way to avoid Lyme disease and other tick-borne illnesses. Blacklegged ticks (also called deer ticks) may be infected with the bacteria that causes Lyme disease. If you live in one of the areas where the incidence of Lyme disease is high, these steps can help.

Know where ticks are likely lurking. Ticks usually crawl up from leaves or blades of grass on the ground to the legs. So be extra careful when walking through fields or meadows and on hikes where you may brush up against bushes, leaves, or trees. Try to walk on well-cleared paths.

Wear protective clothing. Long pants tucked into socks is the best way to keep ticks from crawling up under the pant leg. Lighter-colored clothing can make ticks easier to see.

Use repellents. You can buy clothing that’s pretreated with the insecticide permethrin (which repels ticks). Or you can spray your own clothes and shoes; just be sure to follow the directions carefully. On all exposed skin, use a product that contains DEET, picaridin, oil of lemon eucalyptus (OLE), IR3535, para-menthane-diol (PMD), or 2-undecanone. This search tool from the EPA can help you find a product best suited for your needs. Pay attention to the concentration of active ingredients: for example, at least 20% but not more than 50% with DEET; between 5% to 20% with picaridin; and 10% to 30% with oil of lemon eucalyptus. Many products come in pump spray bottles or as sticks or wipes, which may make them easier to apply where needed.

Get a tick check. After spending time in tick-infested areas, ask a partner to check you for ticks in areas on your body that you can’t see very well. The common bite areas are the back of the knee, the groin, under the arms, under the breasts in women, behind the ears, and at the back of the neck. The tick species that transmits Lyme disease is about the size of a sesame seed. Note that a tick has to be attached to your skin for 24 to 36 hours for it to transmit enough bacteria to give you the disease.

For more information about preventing Lyme disease or living with it, visit the Harvard Health Publishing Lyme Wellness Initiative.

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

Trees enhance life in a multitude of ways. They combat climate change by reducing greenhouse gases in the atmosphere. They muffle sound pollution and reduce air pollution, drawing in carbon dioxide and releasing oxygen. When rain pours from the skies, trees decrease stormwater runoff, preventing flooding and soil erosion. They also provide valuable habitats to support biodiversity in insects, birds, and other animals, and microorganisms. The list goes on.

Equally important is accumulating evidence that simply spending time around trees and green spaces uplifts our health and mood. Below are a few of the biggest benefits we reap.

Keeping it cool: Trees help prevent heat-related illness

Climate change is causing rising temperatures and more heat waves across the US. These effects are worse for those who live in neighborhoods known as urban heat islands, where asphalt and concrete soak up heat during the day and continue to radiate it at night. Temperatures can reach 7° F hotter than suburban, rural, or simply wealthier and leafier neighborhoods.

Trees and their leafy canopy provide shade that helps to prevent urban heat islands. What does that mean for individuals? It translates to fewer heat-related health illnesses, which strike outdoor workers and younger, older, and medically vulnerable people more often. A study published in The Lancet calculated that increasing tree canopy to 30% coverage in 93 European cities could prevent an estimated four in 10 premature heat-related deaths in adults in those cities.

How trees help children: Better mood, behavior, attention, and more

Spending more time in nature has been linked with better health outcomes like lower blood pressure, better sleep, and improvement in many chronic conditions in adults. These findings are prompting a growing interest in forest therapy, a guided outdoor healing practice that leads to overall improved well-being. But what’s also remarkable are the varied benefits of trees and nature for children.

One study of children 4 to 6 years old found that those who lived close to green space demonstrated less hyperactive behavior and scored more highly on attention and visual memory testing measures compared with children who did not.

Just seeing trees can have mental health benefits. In Michigan, a study of children between the ages of 7 and 9 demonstrated that students who could see trees from their school windows had fewer behavioral problems than those with limited views.

In Finland, researchers modified daycare outdoor playscape environments to mimic the forest undergrowth. These daycares were compared to control standard daycares and nature-oriented daycares where children made daily visits to nearby forests. At the end of 28 days, the children in the daycares with modified forest undergrowth playscapes harbored a healthier microbiome and had improved markers of their immune systems as compared to their counterparts.

How green space helps communities

Having green space in neighborhoods also does a lot to enrich the well-being of communities. A randomized trial in a US city planted and maintained grass and trees in previously vacant lots. Researchers then compared these green spaces to lots that were left alone.

In neighborhoods below the poverty line, there was a reduction in crime for areas with greened lots compared to untouched vacant lots. Meanwhile, residents who lived near lots that were greened reported feeling safer and increased their use of the outside space for relaxing and socializing.

How can you help?

Unfortunately, urban tree canopy cover has been declining over the years. To counter this decline, many towns and nonprofit organizations have programs that provide trees for planting.

A few examples in Massachusetts are Canopy Crew in Cambridge and Speak for the Trees in Boston. (Speak for the Trees also offers helpful information on selecting and caring for trees). Neighborhood Forest provides trees for schools and other youth organizations across the US. Look for a program near you!

Planting trees native to your region will better suit the local conditions, wildlife, and ecosystem. Contact your regional Native Plant Society for more information and guidance. If you are worried about seasonal allergies from tree pollen, many tree organizations or certified arborists can give you guidance on the best native tree selections.

If planting trees is not for you but you are interested in contributing to the mission, consider donating to organizations that support reforestation, like The Canopy Project and the Arbor Day Foundation.

About the Author

Wynne Armand, MD, Contributor

Dr. Wynne Armand is a physician at Massachusetts General Hospital (MGH), where she provides primary care; an assistant professor in medicine at Harvard Medical School; and associate director of the MGH Center for the Environment and … See Full Bio View all posts by Wynne Armand, MD

My favorite summer activities officially kick in when the calendar flips to May. It's prime time for open water swimming, running, cycling, hiking, and anything else that gets me outside and moving. Yet, my first step is to get my legs in shape.

“Legs are the foundation for most activities,” says Vijay Daryanani, a physical therapist at Harvard-affiliated Spaulding Rehabilitation Hospital. “They're home to some of the body’s largest muscles, and building healthy legs can improve one’s performance, reduce injury, and increase endurance.”

Four leg muscle groups to build for summer activities

Four muscles do the most leg work: quadriceps, gluteus maximus (glutes), hamstrings, and calves. Here is a look at each.

Quadriceps (quads). Also known as the thigh muscles, the quads are a group of four muscles (hence the prefix "quad'). They extend your leg at the knee and power every leg action: stand, walk, run, kick, and climb.

Glutes. The body’s largest muscles, the glutes (your buttock muscles) keep you upright and help the hips and thighs propel your body forward.

Hamstrings. The hamstrings are a group of three muscles that run along the back of your thighs from the hip to just below the knee. They allow you to extend your leg straight behind your body and support hip and knee movements.

Calves. Three muscles make up the calf, which sits in the back of the lower leg, beginning below the knee and extending to the ankle. They work together to move your foot and lower leg and push you forward when you walk or run.

Spotlight muscle strength and length

Strength and length are the most important focus for building summer-ready legs, says Daryanani. “Strengthening leg muscles increases power and endurance, and lengthening them improves flexibility to protect against injury.”

If you are new to exercise or returning to it after time off, first get your legs accustomed to daily movement. “Start simply by walking around your home nonstop for several minutes each day, or climbing up and down stairs,” says Daryanani.

After that, adopt a walking routine. Every day, walk at a moderate pace for 20 to 30 minutes. You can focus on covering a specific distance (like one or two miles) or taking a certain number of steps by tracking them on your smartphone or fitness tracker. You won’t just build leg strength — you’ll reap a wide range of health benefits.

There are many different leg muscle-building exercises, some focused on specific activities or sports. Below is a three-move routine that targets the four key leg muscles. Add them to your regular workout or do them as a leg-only routine several times a week. (If you have any mobility issues, especially knee or ankle problems, check with your doctor before starting.)

To help lengthen your leg muscles and increase flexibility, try this daily stretching routine that includes several lower-body stretches.

Dumbbell squats

Muscles worked: glutes and quads

Reps: 8-12

Sets: 1-2

Rest: 30-90 seconds between sets

Starting position: Stand with your feet apart. Hold a weight in each hand with your arms at your sides and palms facing inward.

Movement: Slowly bend your hips and knees, leaning forward no more than 45 degrees and lowering your buttocks down and back about eight inches. Pause. Slowly rise to an upright position.

Tips and techniques:

• Don’t round or excessively arch your back

Make it easier: Do the move without holding weights.

Make it harder: Lower yourself at a normal pace. Hold briefly. Stand up quickly.

Reverse lunge

Muscles worked: quads, glutes, hamstrings

Reps: 8-12

Sets: 1-3

Rest: 30-90 seconds between sets

Starting position: Stand straight with your feet together and your arms at your sides, holding dumbbells.

Movement: Step back onto the ball of your left foot, bend your knees, and lower into a lunge. Your right knee should align over your right ankle, and your left knee should point toward (but not touch) the floor. Push off your left foot to stand and return to the starting position. Repeat, stepping back with your right foot to do the lunge on the opposite side. This is one rep.

Tips and techniques:

• Keep your spine neutral when lowering into the lunge.
• Don't lean forward or back.
• As you bend your knees, lower the back knee directly down toward the floor with the thigh perpendicular to the floor.

Make it easier: Do lunges without weights.

Make it harder: Step forward into the lunges, or use heavier weights.

Calf raises

Muscles worked: calves

Reps: 8-12

Sets: 1-2

Rest: 30 seconds between sets

Starting position: Stand with your feet flat on the floor. Hold on to the back of a chair for balance.

Movement: Raise yourself up on the balls of your feet as high as possible. Hold briefly, then lower yourself.

Make it easier: Lift your heels less high off the floor.

Make it harder: Do one-leg calf raises. Tuck one foot behind the other calf before rising on the ball of your foot; do sets for each leg. Or try doing calf raises without holding on to a chair.

About the Author

Matthew Solan, Executive Editor, Harvard Men's Health Watch

Matthew Solan is the executive editor of Harvard Men’s Health Watch. He previously served as executive editor for UCLA Health’s Healthy Years and as a contributor to Duke Medicine’s Health News and Weill Cornell Medical College’s … See Full Bio View all posts by Matthew Solan

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD