Summer Flu: Symptoms, Causes & How to Avoid It

If you come down with a fever, stomachache, or sore throat in the middle of summer, you might think you have the “summer flu.” But despite the name, it's probably not actually the flu.

“The flu is caused by the influenza virus, which peaks in the colder months and is rare during the summer,” says Irene Frantzis, MD, a Columbia pediatric infectious disease specialist. “However, several other viruses easily spread in the summer and cause flu-like symptoms, so we often group those infections together and call them the ‘summer flu.’”

Dr. Frantzis shares what symptoms to watch for, when to see a doctor, and how to lower your family’s risk.

What causes the summer flu?

The term "summer flu" refers to multiple viral illnesses that can look and feel similar to influenza. Common culprits include adenoviruses, enteroviruses like those causing hand, foot, and mouth disease, and occasionally COVID-19. Some bacterial infections, such as foodborne illnesses and tickborne diseases, can also cause flu-like symptoms.

Unlike the flu and other cold-weather viruses that spread mainly through coughing and sneezing, many summer illnesses spread through close physical contact, contaminated surfaces, and shared food and drinks.

Children are especially likely to be exposed to summer viral infections because they spend more time in group settings, like camps, daycares, playgrounds, summer sports, and pools. Infections can then spread to family members and other adults, particularly during picnics and cookouts when sharing food is common.

What are the symptoms of summer viruses?

Many summer viruses cause the same symptoms as a cold or the flu, including:

• Fever
• Sore throat
• Runny nose or congestion
• Headache
• Muscle aches
• Stomach symptoms are especially common during the summer, such as vomiting, diarrhea, stomach pain, or a combination of these symptoms with or without a fever.

How do you treat the summer flu?

Most summer viral infections resolve on their own with rest and hydration. Because vomiting and diarrhea can quickly lead to dehydration, especially in hot weather, drink plenty of fluids or electrolyte solutions.

Prescription medications aren’t effective against most summer viruses: Flu medicines like Tamiflu specifically treat influenza viruses, while antibiotics treat bacterial infections and don’t work against viruses at all. However, you can sometimes find relief with over-the-counter medications, including acetaminophen for fevers and body aches.

When should you call the doctor about summer flu symptoms?

Some elderly people and people with compromised immune systems are at risk for more severe viral infections. Seek medical care if someone is experiencing any of the following:

• Wheezing or trouble breathing
• Signs of dehydration, such as urinating less than usual or crying without tears
• Is unusually sleepy or difficult to wake
• Stiff neck or bad headache
• Red or purple diffuse rash
• Severe pain
• A high fever (above 101ºF or 38.3ºC) lasting more than three days, even without other symptoms

How can you prevent summer illnesses?

You can't avoid every infection, but a few simple habits can reduce your family’s risk:

• Wash hands thoroughly with soap and water, and use hand sanitizer
• Keep sick children home from camp, daycare, and other group activities until they're feeling better
• Avoid sharing drinks, utensils, and food, and encourage kids to do the same
• Practice good hygiene at pools and waterparks, where some stomach viruses can spread if people who are ill enter the water
• Stay up to date on recommended childhood vaccinations, such as chickenpox, measles, and COVID-19
• Keep picnic and cookout foods at cool temperatures and avoid leaving perishable foods sitting out in the heat
• Check for ticks after spending time in wooded or grassy areas

“We don’t have vaccines for a lot of these summer viruses, so hand hygiene is the most important way to avoid getting infected,” says Dr. Frantzis. “Taking these steps can help you and everyone around you stay healthy and enjoy the summer.”

Irene Frantzis, MD, is a pediatric infectious disease specialist and an assistant professor of pediatrics at the Vagelos College of Physicians and Surgeons.