Meet Respiratory Syncytial Virus, a Common Illness You’ve Never Heard Of

Haven’t heard of respiratory syncytial virus before? You’re not alone. But guess what: You’ve probably already had it. 

With COVID-19 cases still high and the start of flu season upon us, it can be stressful to have yet another virus to worry about. RSV is usually mild — but its symptoms can be similar to those of COVID-19 and other viruses. Here’s what you need to know. 

What is respiratory syncytial virus? 

Respiratory syncytial virus (RSV) is one of many respiratory viruses that causes the common cold. Most people get it as infants, but unfortunately you can get it again (and again and again) later in life. 

“We think there’s a pattern where people continually get exposed and reinfected throughout life. Previous infections seems protective against severe symptoms but not against actually getting infected,” says Dr. Amanda Casto, an acting assistant professor in the Division of Allergy & Infectious Diseases at the UW School of Medicine. 

Like other respiratory viruses — think influenza and SARS-CoV-2 — RSV is transmitted through droplets that enter the nose, mouth or eyes. Unlike the flu and COVID-19, infection with RSV usually isn’t serious. Symptoms are usually things like a runny nose, coughing and sneezing. 

Doctors assume RSV is extremely common but don’t really know because most people who have cold-like symptoms don’t get tested to see what virus they have, says Casto. 

“We also think there’s a lot of asymptomatic RSV infection, where people have either no symptoms or really mild symptoms, but we don’t have good numbers on how many people that is,” she says. 

Like other respiratory viruses, cases of RSV tend to ramp up during fall and winter, which Casto says is thought to be from people being indoors more due to colder weather and shorter daylight hours. 

Can RSV cause more serious illness? 

For most people, RSV will feel like a cold and go away within a week or two. But for some people, RSV can lead to serious complications that may require hospitalization. 

The most at-risk group by far is infants. RSV is the most common cause of bronchiolitis (which is similar to bronchitis) and pneumonia in children younger than one year.  

“Kids who are up to six months can end up in the hospital even if otherwise healthy as can older kids who have medical issues,” Casto says. 

Serious illness in infants and young kids is still rare; according to the U.S. Centers for Disease Control and Prevention, only one to two out of every 100 infants who get RSV will need to be hospitalized. 

Still, it's important to recognize symptoms of potential RSV in infants and young kids. The illness may start mild, with symptoms like a runny nose, a cough or wheezing, and less of an appetite. In infants younger than six months, the only symptoms may be things like irritability, decreased activity and appetite, and pauses between breaths. 

If your infant has any of these symptoms, it won't hurt to contact your child's doctor.

People with a condition that suppresses their immune system, such as cancer, are also more at risk for RSV complications. Having a chronic illness, such as asthma or heart disease, and being older than 65, also puts someone at higher risk. 

How can I tell RSV apart from the flu or COVID-19? 

Because of its nonspecific symptoms, it can be hard for adults to distinguish RSV from other respiratory illnesses like the flu and COVID-19, though there are some symptoms that aren’t common with RSV but are with the flu, such as a headache or body aches, or are common with COVID-19, such as shortness of breath or decreased taste or smell.  

One symptom that occurs more with RSV than other respiratory illnesses is ear infections and discomfort, according to Casto.  

There are tests that can identify RSV infection, though these are mostly performed on people who are at risk for severe disease from cold viruses or who are in the hospital. Still, if you develop cold symptoms, you should get tested for COVID-19 and the flu since SARS-CoV-2, influenza, RSV and other cold viruses all cause similar symptoms. 

And if you’re having trouble breathing, have a high fever or have chest pain, you should call 911.  

How should I treat RSV? 

Treating RSV is mostly about keeping yourself or your child comfortable until your immune system does its job and resolves the infection. If you're sick, staying comfortable means taking over-the-counter pain and cold medicines, staying hydrated, and allowing yourself to rest. If your child is sick, consult with their doctor about medications that are safe to give them, and make sure they stay hydrated.

For people with severe disease, an antiviral medication is sometimes given but it is only effective if administered early on in the infection (think a day or so). After a few days, it isn’t as helpful.  

Casto says that there is also a newly developed RSV antibody treatment that can be given to people at high risk or who are hospitalized, but its effectiveness is not yet clear. Other novel treatments are in the works, too, which could potentially become a standard way to protect infants from the virus. 

“There is a lot of research into developing a vaccine for RSV. Given the work that went into the COVID-19 vaccine, we’ve gained knowledge of vaccine development that will probably help speed up the RSV vaccine. There are a few candidate vaccines in trials,” Casto says.