Is it flu or RSV? It can be tough to tell.

The US is seeing a spike in respiratory syncytial virus (RSV) infections, and it’s taking a toll on pediatric hospitals. Beds at these medical centers are filling up, and the limited capacity has prompted drastic measures. Last week, Connecticut Children’s hospital contacted the National Guard to help set up tents in its parking lot to serve as temporary units. At Rainbow Babies & Children’s Hospital in Ohio, staff are turning away emergency room visits that required hospitalization as they reached bed capacity.

RSV, a seasonal respiratory virus that causes cold-like symptoms, has been around for centuries. Today, it is the leading cause of severe respiratory illness in babies and infants. What makes the current outbreak so alarming is that most hospitalized children are older than 2. 

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“We’re seeing a tidal wave of RSV,” says Sharon Nachman, chief of the division of pediatric infectious diseases at Stony Brook Children’s Hospital. “And we’re not seeing it just in those first two years of life that we typically expect but in school-aged children who should have already had their RSV exposure.” Pediatric experts warn that pandemic disruptions have led to a brutal flu and RSV season.

Why is RSV season so bad this year?

Blame the pandemic. Daniel Ganjian, a pediatrician at Providence Saint John’s Health Center, explains that RSV exposure early in life is critical to training the immune system. Most RSV infections happen in babies whose immune systems are still developing. Infected infants may wheeze and cough for two weeks, but most make a full recovery. RSV was estimated to cause 7 percent of infant deaths, with most happening among those younger than 3. 

Having a memory of the virus allows the immune system to build up the necessary defenses to immediately destroy the pathogen the next time they cross paths. But in early 2020, children did not attend daycare or in-person school, lowering the chance of infection and the creation of an appropriate immune defense. “They have zero antibodies because these kids, who were 1 and 2 during the pandemic, were not exposed to RSV,” Ganjian says. “Now they’re getting it for the first time and they’re getting severe reactions,” he says.

[Related: The US may be in for a brutal flu season]

But what about the kids exposed to the virus in the past and are getting severely ill now? Nachman says that’s because our immune response to the virus is short-lived and easily forgettable. It’s only with repeated exposure that the immune response will get a “kick-start” to remember the virus, Nachman says. But, she adds, since these kids did not get exposed to the virus in the past few years, “their body really forgot how to make an immune response to RSV.” 

Is the RSV outbreak related to the flu?

Flu does not cause RSV infections—different viruses are responsible for the different illnesses. But having both circulating at the same time is a recipe for trouble. While your immune system is busy fighting off one virus, another can sneak in and cause infection. “We have families coming concerned their kid has been sick all month with the flu and that’s not true,” Nachman explains. It’s possible for children to appear sick for a month, but it’s likely they had one virus at a time. Even if there was just a small gap between symptoms, “they might have been infected with a second virus, making it seem like they never got better.”

Historically, flu and RSV season rarely overlapped. Before the pandemic, RSV season occurred from late October to December while flu season peaked in December and ended February. However, since most respiratory viruses took a backseat to COVID-19, there have been disruptions to their seasonal circulation. Now, Nachman says, “these viruses never left”: With many people going back to school and the office, there’s more opportunity for the viruses to spread from person to person.

How can you tell the difference between the flu and RSV?

You can’t tell the difference between the flu and RSV just by looking at someone. Adults and older children can get RSV, too, but in healthy individuals signs of infection are often mild. Both viruses cause similar symptoms such as congestion, cough, and runny noses. In RSV, though, not all symptoms appear at once, and very young infants may experience issues with breathing and irritability. “If your child is having difficulty speaking or you see they’re breathing faster, wheezing with a whistling sound, then you have to go to the pediatrics office to get tested,” says Ganjian. 

If you suspect RSV, you can take a rapid RSV antigen test at a pediatric office or urgent care site. The RSV antigen test detects active viral proteins using a nasal swab, with results provided to you in minutes. 

There is no specific medication or treatment for an RSV infection—although there are clinical trials underway for an RSV vaccine. However, there are ways to relieve symptoms. Since babies are mostly “nose breathers,” Ganjian recommends using a saline vaporize or a nasal suction to remove mucus and relieve nasal congestion. You will also want to keep your child hydrated and use acetaminophen and ibuprofen (never aspirin) to manage any fever or pain. 

How can you protect your family from RSV?

To avoid respiratory infections this fall and winter, experts recommend having children practice good hygiene such as washing their hands before they eat or after being outside, as well as showering and changing clothes once they get home from school. You also want to keep your child’s immune system strong—that requires getting enough sleep and making sure they’re eating foods such as broccoli and sweet potatoes.

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If your child is showing signs of being sick, doctors recommend keeping them at home and avoiding crowded areas. Not only are you helping to contain viral spread, but you’re reducing the risk of your child getting a second infection. Since babies and toddlers under 2 cannot wear face masks, Nachman recommends that parents wear masks when outside to avoid bringing any viruses home.