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Flu and COVID Cases Are Surging: How to Protect Yourself

BY KATHY KATELLA January 4, 2024

Annual flu and updated COVID vaccines, as well as RSV vaccines and a monoclonal antibody, are tools to prevent a “tripledemic”—flu, COVID, and RSV hitting at once.

[Originally published: Oct. 17, 2023. Updated: Jan. 4, 2024]

The new year has brought a surge in flu and COVID-19 cases at a time when experts are monitoring both viruses, as well as respiratory syncytial virus (RSV). All three illnesses have swept through the United States during the past several winters, causing severe illness in vulnerable people and overwhelming hospitals with pediatric and adult patients.

This year, flu is on the rise in most parts of the country, according to a recent Centers for Disease Control and Prevention (CDC) report. COVID cases and hospitalizations have also been ticking upward.

The good news is that, for the first time, there are better tools to prevent—or minimize the effects of—these diseases. It’s not too late to get a flu shot or an updated COVID vaccine, and there are vaccines and a monoclonal antibody injection for those most vulnerable to RSV. How much they will help head off the threat of a so-called “tripledemic”—all three diseases hitting at once—is still difficult to say.

“There are predictive models,” says Shana Gleeson, MD, a Yale Medicine infectious diseases specialist. “But we can’t say for sure how it's all going to play out.”

One potential factor is how many people get the new shots, Dr. Gleeson explains. “Another is how much more likely these viruses will be to spread at a time when most people have stopped wearing masks and taking other precautions, such as avoiding crowded, enclosed spaces,” she says.

Below, Yale Medicine experts tell you what you need to know to keep yourself and your family safe from influenza, COVID, and RSV.

What is the difference between flu, COVID, and RSV?

All three of these respiratory illnesses are caused by highly contagious viruses. They all cause cold-like symptoms, such as cough and runny nose. However, each has unique features, such as loss of taste or smell with COVID (although the latter symptom is reported to be less frequent than it was before the Omicron variant), and wheezing in children with RSV.

While many people experience mild illness from these viruses, factors like age and general health put some at higher risk for hospitalization and death. In the case of COVID, even healthy young people have developed Long COVID, defined as signs, symptoms, and conditions that can continue for weeks, months, or years beyond the initial infection or develop later.

Flu can come on fast and cause the entire body to ache within a couple of days. COVID symptoms may appear two to 14 days after exposure to the virus, while RSV takes four to six days; in the latter two diseases, symptoms build slowly.

If you get sick from any of these illnesses, it may be difficult to figure out which one you have, although a rapid home test may rule out COVID, and a doctor can provide laboratory tests for flu and RSV, if necessary.


Flu is a common illness during the winter. But it can be severe, especially in children younger than age 5 and adults ages 65 and older, pregnant women, and those with compromised immune systems and chronic conditions, such as diabetes or asthma. It attacks the respiratory system, causing fever, body aches, cough, headache, and sore throat.

How to prevent the flu: Get the annual flu shot, which is available to everyone ages 6 months and older. Although the CDC recommends getting the shot by the end of October for peak protection, it is given throughout the season, which usually peaks between December and February, and can extend until May.

Most people ages 6 months and older need only one dose of the flu vaccine; however, some children, ages 6 months through 8 years, may require two doses for the best protection.

“Some people will still get the flu after getting the vaccine,” Dr. Gleeson says. “But data suggests that if you do, the vaccine decreases the risk of severe disease and hospitalization. You might feel bad, but not as dramatically ill as you would have been if you didn't get the vaccine.”

This year, special measures for flu vaccination are no longer recommended for people with egg allergies, regardless of the severity of a previous reaction to egg. This is based on studies that show those severe allergic reactions are rare, according to the CDC, which also recommends all vaccines be given in settings where allergic reactions can be recognized and treated quickly. People with allergies to other vaccine ingredients should talk to their providers.

If you get the flu: The CDC recommends staying home for at least 24 hours after your fever is gone. The fever should go away on its own without over-the-counter medication, according to the CDC. Also, children and teenagers should not take aspirin or products that contain salicylate to treat flu symptoms, since that ingredient can cause a rare condition called Reye’s syndrome in people 18 and younger.

You can talk to your doctor about getting a prescription for an antiviral drug, such as Tamiflu, especially if you are 65 or older, pregnant, or have a medical condition such as asthma or heart disease. Children can take these medications as well. Antiviral drugs, including pills, inhaled powders, and solutions delivered intravenously, fight the flu virus in your body, and they work best when you start taking them early, one or two days after symptoms start. Antivirals can help reduce symptoms, shorten your illness by one or two days, and prevent pneumonia and other serious complications, including death.


COVID cases rates are rising. A particular concern is the recent emergence of new Omicron subvariants, including JN.1, which quickly rose to become the dominant variant in the U.S. over the last months of 2023.

How to prevent COVID: Get one of the updated mRNA vaccines from Pfizer-BioNTech or Moderna, recommended for everyone ages 6 months and older, or the updated shot from Novavax for ages 12 and older. These shots were made to protect against XBB.1.5, an Omicron subvariant that was circulating widely earlier this year, and they are expected to prevent infection and severe disease from descendants and relatives of the XBB strain that are circulating now, according to the CDC. The agency also states that existing COVID vaccines, tests, and treatments still work well against JN.1.

If you get COVID: You should stay home for at least five days to avoid spreading it to others. Most people have mild illness and can recover at home with the help of rest, fluids, and over-the-counter medicines if needed. Talk to your doctor about the three prescription-only antiviral medications if you have mild or moderate COVID and are at high risk for severe disease. (You are at higher risk if you have an underlying medical condition, such as asthma, cancer, or heart disease, or a weakened immune system. Risk also starts to rise with age, starting at age 50.) You must take these medications as soon as possible after noticing symptoms.

The National Institutes of Health (NIH) recommends three antiviral therapies in order of preference, starting with Paxlovid™ (nirmatrelvir and ritonavir), a pill for children and adults ages 12 and up. Paxlovid must be taken within the first five days after noticing symptoms. Pills can be prescribed by a health care provider or, in some cases, a pharmacist, and taken at home.

Remdesivir (Veklury®), the second choice on the NIH list, is for use when Paxlovid is not available or clinically appropriate. It can help adults and children who are at least 28 days old or weigh at least 7 pounds and who may or may not be hospitalized. It must be taken within seven days of when symptoms start. Remdesivir is given intravenously at a health care facility for three consecutive days.

The third option is molnupiravir (Lagevrio™), a pill for adults to be taken twice a day for five days starting as soon as possible within five days after symptoms begin.


RSV is a common winter virus that can cause a cold-like illness. Most healthy children older than age 2 and adults younger than age 60 will have a mild case of RSV that will get better in about a week. However, people 60 and older can develop lower respiratory tract disease from RSV, leading to inflammatory conditions such as pneumonia and bronchiolitis.

Also at higher risk are premature infants, infants up to 12 months (especially those 6 months and younger), and children younger than 2 years with chronic lung disease, congenital heart disease, weakened immune systems, and/or neuromuscular disorders. Those groups are at risk for hospitalization and death from RSV, and there are no treatments beyond supportive care.

How to prevent RSV: If you are eligible, get an RSV vaccine, which can prevent an infection from spreading to the lower respiratory tract. If you are 60 or older, you can choose between two new vaccines: Arexvy™, developed by GSK, or Abrysvo™, from Pfizer. You can decide whether an RSV vaccine is right for you based on “shared clinical decision-making,” according to the CDC, meaning you may receive a single dose based on discussions with your health care provider.

The Abrysvo vaccine is administered to pregnant women to provide them with protective antibodies that will be passed on to their fetuses to protect their newborns for their first six months of life. The CDC Advisory Committee on Immunization Practices (ACIP) recommended the vaccine for seasonal use in most parts of the country, meaning that it should be given to pregnant people who would reach 32 to 36 weeks of gestation—the point when the vaccine can be given—during the period of September to January to protect babies born between October and March, when the risk of RSV infection is traditionally highest.

From February to August, parents of small children approaching their first RSV season should talk to their pediatricians about a new immunization, a monoclonal antibody called nirsevimab (brand name Beyfortus™). This is a shot for infants up to 8 months old, born during—or entering—their first RSV season, and for a small group during their second season if they are between 8 and 19 months old and at high risk for severe disease (including children who are severely immunocompromised).

Most babies who have protection against RSV from the vaccine given to their mother while she was pregnant should not need further protection from the monoclonal antibody, according to the CDC.

An older monoclonal antibody called Palivizumab (Synagis®) is also available. It’s given as intramuscular injections starting before the start of the RSV season, and then usually once a month throughout the season to infants and young children who are at increased risk of severe RSV disease based on gestational age and certain underlying medical conditions.

If you get RSV: Stay home when you’re sick—people infected with RSV may be contagious for three to eight days. Most people will have mild symptoms and get better in a week or two. Supportive care includes drinking plenty of fluids to prevent dehydration and taking over-the-counter medications for discomfort and fever. Dehydration, ear pain, or trouble breathing may be signs of a secondary infection that could become serious enough to require hospitalization, which might include treatment with intravenous fluids, oxygen therapy, or mechanical ventilation.

Should you get all three vaccinations (if eligible) at the same time?

The CDC considers it safe to get the COVID-19 and flu vaccines at the same time. Research is in progress to explore the effects of administering both vaccines in a single shot.

But the RSV vaccines for older adults and pregnant women (who can pass the antibodies along to their newborns) are new, and there isn’t data at this time to say for sure whether giving those at the same time as the other two shots is the best strategy.

People who get more than one vaccine in the same visit may experience more side effects, Dr. Gleeson explains. "You may notice increased side effects, such as fatigue, muscle aches, and soreness at the injection site, if you get them on the same day,” she says. “However, most side effects remain mild and are short-lived, even in people who get both vaccines at the same time.”

What other steps can you take to avoid infections?

While vaccines offer strong protection, they may not always protect against infection, so it’s wise to take additional precautions. For COVID, this may include keeping home tests on hand to use if you feel sick so you can avoid spreading the virus if you have it. You can order COVID-19 rapid tests for free from the government.

Other strategies to prevent winter respiratory viruses, provided by the CDC, include:

  • Practicing strategic masking, which means wearing well-fitting masks or respirators that cover your mouth and nose when people around you are coughing, sneezing, or talking—or whenever you feel it is appropriate.
  • Improving indoor air quality by using air filters or opening windows.
  • Using household cleaners that contain soap or detergent to remove dirt and germs from surfaces. Use a weaker bleach solution or EPA-sanitizing spray to sanitize surfaces or objects.
  • Practicing hand hygiene.
  • Staying away from people who are sick. The closer you are to a greater number of people, the more likely you are to be exposed to a respiratory virus.

The CDC is monitoring all three diseases. If you want to know whether they are spreading in your area, you can check the CDC website for COVID-19 hospitalizations in your county, weekly flu maps, or RSV trends.