What’s the Difference Between RSV, the Flu and COVID-19?

It comes down to a wheeze, a fever and long-term effects
Person taking electronic temperature of sick child in bed.

As if parenting wasn’t hard enough, COVID-19 has made the “sick kid questions” even more confusing: Is it just a cold or something else? Can I send my child to school? When should I call their healthcare provider?

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“Every child runs a gauntlet of infections during the first five years of their life,” says pediatric infectious disease specialist Frank Esper, MD. “Navigating childhood illnesses can be challenging for parents.”

Can RSV and flu be mistaken for COVID-19?

RSV, flu and COVID-19 are respiratory viruses. These viruses affect your respiratory system — the network of tissues and organs that help you breathe. “Cough, runny nose and fever are common to all respiratory viruses,” says Dr. Esper. “When I see a child with these symptoms, I usually rely on a laboratory test to make an accurate diagnosis.”

But there are some subtle differences between RSV, flu and COVID-19.

Symptoms unique to RSV

RSV, or respiratory syncytial virus, is a virus nearly all children get by age 2. In addition to a cough, runny nose and fever, a unique symptom of RSV is wheezing. A wheeze sounds like a whistle or rattle when your child breathes.

Most children recover from RSV on their own, but sometimes, it can lead to severe illnesses such as:

  • Bronchiolitis, swelling of the small airways in your child’s lungs.
  • Pneumonia, an infection of your child’s lungs.

RSV can infect people of any age but is most serious for young children and older adults. Hospitals admit nearly 60,000 children under age 5 for RSV every year.

Symptoms unique to flu

A distinctive sign of the flu is a very high fever. Along with other respiratory symptoms, the flu often causes high fevers of 103 or 104 degrees Fahrenheit (39.44 or 40 degrees Celsius). People usually feel miserable, more so than with other viruses, says Dr. Esper. This can include nausea and vomiting as well, which, though not unique to the flu, is also often worse than with other viruses.

Children under age 5, and especially under age 2, are at higher risk of complications from the flu. These include:

Each year, between 7,000 and 26,000 children develop symptoms serious enough to require hospitalization.

Symptoms unique to COVID-19

The signs of COVID-19 are similar to flu and RSV. But unlike the other viruses, COVID-19 can have a serious effect on body systems outside the lungs. “Flu can do this too, but the symptoms usually go away once the virus leaves your lungs,” states Dr. Esper. “COVID can cause long-term effects, such as brain fog.”  

Several symptoms you may think are unique to COVID-19 are actually common among respiratory viruses. For example:

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  • Loss of taste and smell: Many viruses, including those that cause the common cold and flu, can affect your sense of taste and smell.
  • Vomiting and diarrhea: Up to 30% of children with respiratory viruses have gastrointestinal symptoms, says Dr. Esper.

Other tools to help diagnose respiratory viruses

Providers often use disease surveillance systems to help make diagnoses. Surveillance shows the circulation patterns of respiratory viruses across the U.S. and over time. This information can be a clue when evaluating patients. If the surveillance system shows that a certain disease is circulating a lot in your area, that can help guide your provider toward a diagnosis.

The circulation of respiratory illnesses is often seasonal, though COVID-19 has changed this. For example, before the pandemic, RSV peaked in the winter. “If we saw a baby with a wheeze in the winter, it was likely RSV,” says Dr. Esper. “But in 2021, RSV peaked in July. This was shortly after things started opening back up.”

In 2022, Dr. Esper says RSV continues to be off-cycle. It started circulating in August and has peaked in October, with a positivity rate reaching 41% in young children (0 to 5 years old) and 28% in elementary-aged children (6 to 12 years old) the week of October 17.

The 2021-2022 flu season was also off its usual schedule and went on longer than normal. “Usually, flu peaks between December and February and is over by April,” notes Dr. Esper. “But it was going strong into this past May.”

Although it’s still too early to determine how the flu might circulate during the 2022-2023 flu season, you can take steps to protect yourself. “We currently don’t know when to expect the peak flu,” says Dr. Esper, “so it’s good to get your flu shot now if you haven’t already done so.”

Want to know what viruses are circulating in your area? Check out the national surveillance programs for flu, COVID-19 and other viruses.

Home testing now and in the future

If your child has a runny nose, cough and fever — the telltale signs of a respiratory virus — a COVID-19 test is a good first step. Knowing if your child has COVID-19 can help you protect other family members and prevent the spread outside of your household.

Many clinics use a triple test that can detect flu, RSV and COVID-19. Dr. Esper predicts parents may soon have triple tests for home use as well. 

“Before the pandemic, home tests for respiratory viruses were not available,” he says. “Now, pharmacy shelves are stocked with COVID antigen tests. It won’t be long before home tests include flu and RSV.”

In the last year, you could buy an at-home PCR test that includes testing for COVID, flu and RSV. But Dr. Esper notes you won’t get immediate results because you have to send the sample to a lab for processing. “The processing time is 24 to 48 hours after they receive the test,” he explains. “Therefore, it can be several days before you find the results.”

Home testing for flu and RSV has many benefits:

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  • Early identification of flu could help people get the treatment they need quicker. Early treatment with a medication called Tamiflu® significantly reduces how long you’re sick with the flu.
  • A diagnosis of RSV at home could help you know when to keep your baby out of daycare. This could protect other children from RSV, which spreads rapidly in childcare settings.
  • An RSV diagnosis is also helpful to isolate your child from family members who are prone to getting bad lung infections.

Can my child have a co-infection with more than one virus?

Co-infection — when you have multiple viruses at once — is common in children. In any childcare or preschool room, you’ll find children sick with a range of viruses. “When they’re all coughing, it’s not surprising that a child can catch two or even three viruses at the same time,” states Dr. Esper. “We saw co-infections before the pandemic, and we’re seeing them now with RSV, flu and COVID-19.”

Dr. Esper hasn’t seen any evidence that having more than one virus leads to worse symptoms or outcomes, though. Providers treat infections the same way, whether there are one or three.

How to prevent respiratory illnesses

One thing COVID-19 taught people is how to prevent viral illnesses. COVID-19 prevention strategies were also very effective at preventing flu and RSV.

In addition to wearing a mask and physical distancing, these steps can reduce your risk of respiratory infections:

  • Get your child vaccinated for flu and COVID-19 (if your child is eligible).
  • Sanitize high-contact surfaces, such as desks, tables and doorknobs if someone in your household is sick.
  • Wash your hands regularly or use hand sanitizer.

Additionally, it’s helpful to keep your child home if they’re sick. This minimizes the risk of spreading illness to other children at school.

When to call their healthcare provider

Children usually recover from respiratory viruses on their own with rest and fluids. Dr. Esper recommends reaching out to your child’s healthcare provider if they have:

  • Trouble breathing.
  • Severe vomiting and diarrhea to a point where they’re not eating or drinking.
  • Symptoms that aren’t improving or are getting worse after five days.

If your child has a high fever and you suspect it’s the flu, get in touch with their provider right away. Early treatment with Tamiflu within the first two days of symptoms can help your child get better faster.  

Also check with your provider sooner if your child has any underlying health conditions, such as:

Respiratory infections are common in childhood. While you can take steps to reduce your child’s risk, you can’t avoid them entirely. If your child is sick, keep them home to reduce the spread of infection to others in your community. As they recover, your child will develop immunity that will help protect them from future infections.

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