RSV: What to Know About Symptoms, Transmission and Treatment - The New York Times

Before the Covid pandemic, most people caught respiratory syncytial virus before the age of 2. Now things have changed.

You may have seen respiratory syncytial virus, or R.S.V., in the news recently, as rates of the virus have ticked up across the United States. R.S.V. usually circulates from late December to mid-February. But this year, an early spike in cases is resulting in markedly higher numbers of infections and hospitalizations.

As rising R.S.V. rates coincide with the expected wintertime surge in Covid-19 as well as an early flu season, experts are worried about a "tripledemic" and the strain it could place on hospitals and emergency departments that are already stretched thin.

Here's what to know about R.S.V., who is most at risk and what you can do to avoid getting sick.

What is R.S.V. and why is it on the rise?

R.S.V. is a common winter virus that typically causes mild cold-like illness in most people, but can occasionally be very dangerous for young children and older adults, said Emily Martin, an associate professor of epidemiology at the University of Michigan School of Public Health.

"The youngest infants have a high risk of coming into the hospital in what we call their first R.S.V. season," Dr. Martin said. "If a child is born in the summer and they get exposed for the first time in the winter, they are at risk of having more serious disease. But many infants didn't experience the first R.S.V. season on the regular schedule that they would have, particularly if they were born in or after 2020."

In a normal prepandemic year, 1 to 2 percent of babies younger than 6 months with an R.S.V. infection may need to be hospitalized. And virtually all children have gotten an R.S.V. infection by the time they are 2 years old.

But many experts believe masking, social distancing, school closures and other precautions taken during the first year or two of the pandemic protected most children from exposure to the virus and other germs. "As a result, there are still many children who are less than 3 years old who've never been exposed to R.S.V.," said Dr. James Antoon, an assistant professor of pediatrics and pediatric hospitalist at Monroe Carell Jr. Children's Hospital at Vanderbilt University in Nashville, Tenn. "The virus is now playing catch-up in all these kids."

Can adults get R.S.V.?

They can. "Adults still get R.S.V. fairly regularly and they can get reinfected multiple times throughout adulthood," Dr. Martin said. Because adults already have a lot of antibodies against the virus from previous exposures, their illness tends to be much milder. In fact, it can be almost indistinguishable from the common cold or even a mild case of the flu or Covid-19, she said.

Most adults with R.S.V. are able to shake off an infection in a week or two, but seniors and those who have weakened immune systems, as well as those with chronic lung or heart disease, can develop more severe cases. According to the Centers for Disease Control and Prevention, an estimated 177,000 older adults are hospitalized with R.S.V. each year and 14,000 of them die.

What are the symptoms of an R.S.V. infection?

In adults and children, R.S.V. typically causes mild symptoms like a cough, runny nose and fever. These appear gradually, four to six days after getting exposed. In young babies, the only signs of an infection may be general lethargy, irritability and a decreased appetite, said Dr. Priya Soni, a pediatric infectious disease specialist at Cedars-Sinai Guerin Children's in Los Angeles. Parents should also be on the lookout for signs that their child is having difficulty breathing, Dr. Soni said. For example, if an infant or toddler is breathing faster than usual, if you notice more of their ribs or belly moving as they breathe or if their nostrils are flaring, those are all signs that you should take them to see a doctor.

Young children tend to struggle more, not just because their immune systems are still learning to recognize and fight off viruses, but also because their airways are so small, Dr. Soni said. An R.S.V. infection can dramatically increase mucus secretions in the airways, which older children and adults are able to cough or sneeze out. But infants and toddlers do not yet have strong enough muscles to cough up all the extra fluid, so parents or health care providers need to do the job for them by suctioning their airways.

If mucus collects in the small airways in the lungs, it can cause blockages and inflammation known as bronchiolitis, which is one of the most common complications that results in hospitalization. Another outcome of severe R.S.V. in young children is pneumonia. Several studies have also linked severe R.S.V. to an increased risk of recurrent wheezing and asthma later in life. "R.S.V. can be extremely disruptive to young lungs," Dr. Martin said.

Those at highest risk for severe infections include premature infants, babies under 6 months of age, infants and toddlers with chronic lung disease or congenital heart disease, as well as children with weakened immune systems and those who have neuromuscular disorders that make it difficult to clear out mucus.

Is there a test for R.S.V.?

There are rapid antigen tests and P.C.R. tests to check for R.S.V., but they are typically reserved for young children or older adults, because there is no treatment for an infection if you do not need hospitalization, Dr. Soni said. If a patient is showing signs of a severe infection, a health care provider may also check their breathing with a stethoscope and order a white blood cell count or other tests, such as a chest X-ray or CT scan.

What can you do to avoid R.S.V.?

Unlike Covid, R.S.V. can spread when people touch contaminated surfaces. It also spreads through respiratory droplets, Dr. Martin said. So it's a good idea to disinfect surfaces, particularly in settings like day care centers, where young children are constantly touching things, sneezing on things and sticking them in their mouths.

Premature infants and children with certain medical conditions can also take a monthly monoclonal antibody medication called Palivizumab during R.S.V. season to help keep them out of the hospital.

Although several vaccines in clinical trials have started to show promise for R.S.V., none are available yet. That's why experts recommend more general measures to prevent infection, such as frequent hand-washing — and for those who are sick, staying home.