Is It COVID, Flu, or RSV? Here's How to Really Know What's Making You Sick

These clues can help you figure out which virus you may have.

healthcare provider swabbing senior male for viruses

Pekic/Getty Images

  • The U.S. is in the midst of a "tripledemic" with COVID, flu, and RSV cases and hospitalizations rising.
  • All three respiratory illnesses have very similar symptoms—including fever, cough, and fatigue—and it can be difficult to determine which virus you have based on symptoms alone.
  • The only true way to know which virus you have is to get tested, preferably in a clinical setting that can test for multiple viruses at once.

COVID, flu, RSV—all three respiratory illnesses are driving what’s being called a “tripledemic” in the United States right now, as cases continue to rise and hospital beds fill up.

So far this season, the Centers for Disease Control and Prevention (CDC) estimates that there have been at least 15 million flu illnesses—an unusually high number this early on.

Rates of respiratory syncytial virus (RSV) hospitalizations also continue to be the highest they’ve been since the CDC began tracking the illness during the 2018–2019 season.

COVID, too, continues to circulate, with 44% of U.S. counties currently experiencing medium to high community levels.

All three respiratory illnesses cause similar symptoms, and with so much symptom overlap, it can be difficult to determine which illness you have based on symptoms alone. But experts say that knowing which virus you have can still be useful for knowing treatment options or potentially protecting others from becoming ill.

Here’s what to consider if you’ve come down with a low-grade fever or pesky cough—including the only sure-fire way to know what virus you’re dealing with.

Symptoms May Offer Some Insight

Fever, cough, sore throat, congestion or runny nose—these symptoms can show up if you have either RSV, COVID, or flu.

“The presentation of these respiratory virus infections overlaps pretty substantially,” David Kimberlin, MD, co-director of the division of pediatric infectious diseases at the University of Alabama and Children’s of Alabama, told Health.

Symptoms of Flu, RSV, and COVID-19
Fever or chills Usually Common Common
Cough Common Common Common 
Shortness of breath Rarely Sometimes* Common
Fatigue Usually Sometimes Common
Muscle or body aches Usually Sometimes Common
Headache Common Sometimes Common
New loss of taste or smell Rarely Rarely Sometimes
Sore throat Sometimes Sometimes Common
Congestion or runny nose Sometimes  Usually Common
Nausea or vomiting Sometimes* Rarely Sometimes
Diarrhea Sometimes* Rarely Sometimes
Loss of appetite Sometimes Common Sometimes
Sneezing Sometimes Common Rarely
Wheezing Rarely Common Rarely
*Nausea, vomiting, and diarrhea from flu; shortness of breath from RSV more common in children. Sources: Centers for Disease Control and Prevention, National Library of Medicine, National Institutes of Health

Onset of symptoms may also be able to provide you with clues. Flu in particular has been known to have a very short incubation period with symptoms showing soon after exposure—anywhere from two to four days from when a person was infected.

In addition to a short incubation period, flu symptoms tend to come on quickly and all at once, according to Beth Thielen, MD, a physician-scientist in the University of Minnesota’s Division of Pediatric Infectious Diseases. Many people with flu say it feels as though they’ve been hit by a truck when symptoms appear.

Meanwhile, COVID and RSV tend to be more gradual in their symptom onset, and have a slightly longer incubation period. Depending on which variant you've been infected with, COVID's incubation period can range from two to 14 days after exposure; RSV has an incubation period of four to eight days.

Trying to diagnose yourself based off of symptoms and symptom onset alone, however, isn’t fool-proof.

“There is not a precise way short of doing molecular testing to be able to say with any certainty what [you have],” said Dr. Kimberlin.

Age, Location Matters for Viruses

According to Dr. Kimberlin, which virus you may have been infected with may depend on where you are in the country.

The latest CDC data show that the large majority states in the US have high or very high respiratory illness activity—that's defined as presenting with a fever along with a cough or sore throat. Meanwhile, though COVID cases may be slowly rising, more than half of communities in the US are still listed as having low community transmission levels.

RSV produces illness in both children and adults, but it has largely affected children this season, and it can be particularly dangerous for them. If a child is experiencing a respiratory illness right now, RSV is a top contender.

“If you are a younger child and you have bronchitis, right now is it more likely to be RSV,” said Dr. Kimberlin, who also noted that, after that, the illness could be due to metapneumovirus or parainfluenza viruses—both of which can cause respiratory infections.

COVID, too, is a possibility for that age group, “but it’s less likely to be flu or a run-of-the-mill cold caused by a rhinovirus,” said Dr. Kimberlin.

If you’re an adult, however—particularly one with a cough, fever, congestion, and runny nose—it’s most likely to be flu, with COVID coming in at a close second.

Older adults, very young children, and people with weakened immune systems or underlying medical conditions are at an increased risk of severe infection from RSV, flu, COVID, or all three.

Importance of Knowing Which Virus You Have

The only true way to know which virus you can attribute your symptoms to is to take a test—but with similar symptoms for all three viruses, is it even necessary to know your exact diagnosis? Experts say it can be.

Although at-home COVID tests are available, PCR tests—or tests that you can get in a clinical setting—are still more accurate. Healthcare providers can also test for multiple viruses at once, which can be especially beneficial if your symptoms match all three viruses.

Knowing what you have can give you more information to provide anyone you may have infected, especially those who are high-risk. It can also get you feeling better faster.

“We do have treatments for influenza, which are particularly recommended for young children and older adults and immunocompromised folks,” said Dr. Thielen, adding that they can shave a day off of illness for anyone.

Paxlovid, the antiviral treatment available for COVID, is also available for people at high risk of developing severe disease from infection. Paxlovid is prescription-only and has shown to reduce the risk of hospitalization or death by 88%, but it does come with the risk of Paxlovid rebound, or the recurrence of COVID symptoms following treatment. However, rebound illness has also affected people who haven’t taken Paxlovid.

Different Viruses, Similar Prevention Measures

According to Dr. Kimberlin, all of these viruses are caused by a person-to-person contact through infected respiratory droplets—that typically means inhaling virus-laden droplets from the air when an infected person is talking, coughing, sneezing, or otherwise ejecting them from their mouth or nose. You can also pick them up on surfaces and transport them to your nose, eyes or mouth.

For COVID and flu, safe and effective vaccines are available. Though they may not protect against symptomatic disease entirely, vaccines can greatly reduce the risk of hospitalization and death, and potentially lessen symptoms if you do end up getting a breakthrough infection.

In addition to available vaccines, the same precautions used during the COVID pandemic are helpful regardless of the virus at hand.

“Much of what we learned so painfully during the pandemic can be applied here,” said Dr. Kimberlin. “Use common sense, wash your hands frequently, don’t touch your face, wear a mask, make sure you’re in a place that’s pretty well-ventilated.”

According to Dr. Thielen, the best plan of action is to take a multi-layered approach.

“No one technique is 100% effective, but if you layer a few techniques, it can really reduce the chances of contracting a number of viruses and can reduce the severity of illness if you do,” she said.

Both emphasized the importance of staying home if you’re sick, even if it isn’t COVID.

“Take the lessons learned from COVID and apply them to the other things that are making you sick. Just because it’s not COVID does not mean it’s not something that is bad,” said Dr. Kimberlin. “We have to be responsible in order to protect one another.”

Was this page helpful?
7 Sources uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Weekly U.S. influenza surveillance report.

  2. Centers for Disease Control and Prevention. RSV-NET interactive dashboard.

  3. Centers for Disease Control and Prevention. COVID-19 integrated county view.

  4. American Lung Association. Learn about flu.

  5. Manti S, Cuppari C, Lanzafame A, et al. Detection of respiratory syncytial virus (RSV) at birth in a newborn with respiratory distressPediatr Pulmonol. 2017;52(10):E81-E84. doi:10.1002/ppul.23775.

  6. Centers for Disease Control and Prevention. Symptoms of COVID-19.

  7. Administration for Strategic Preparedness & Respone. Paxlovid.

Related Articles