What Is RSV (Respiratory Syncytial Virus)? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Respiratory syncytial virus (RSV) is a common germ that can infect the nose, throat, lungs, and breathing passages.

For most healthy children and adults, RSV can result in mild, cold-like symptoms. But RSV can be serious and even life-threatening for the very young, the old, and people with weakened immune systems or underlying lung or heart disease.

Though many people have never heard of this virus, “RSV is so common that pretty much everyone gets it by the time they are 2 years old,” says Denise McCulloch, MD, MPH, an infectious disease physician-scientist at the University of Washington School of Medicine in Seattle.

RSV circulates in most parts of the country from November to April — the so-called “RSV season” — and typically peaks in January and February. But the arrival of COVID-19 in 2020 upended RSV’s usual pattern.

Measures like mask mandates and social distancing, designed to prevent COVID-19 transmission, also kept RSV levels low during the early years of the pandemic. But once large numbers of people began gathering mask-free again, RSV came back strong.

The 2022–2023 winter RSV season in the United States kicked off unusually early, in October, with numerous outbreaks among children that strained hospitals. An abnormally high number of seniors contracted RSV as well.

While infectious disease experts anticipate that RSV will eventually return to its typical late fall-winter pattern, it may continue to be off-kilter for a while. “At this point, we really need to be on the lookout for RSV at any time of year,” says Marian Michaels, MD, MPH, a professor in the division of pediatric infectious diseases at the University of Pittsburgh School of Medicine.

Symptoms of RSV tend to show up four to six days after getting infected, notes Mayo Clinic. For most children past 6 months old and adults who get RSV, symptoms are similar to the common cold:

• Runny nose
• Congestion
• Mild headache
• Sore throat
• Cough
• Fever
• Tiredness

Symptoms generally last three to seven days, though a cough can linger for a couple of weeks.

Infants don’t always show these symptoms, notes the Centers for Disease Control (CDC). In babies less than 6 months old, the only symptoms of RSV infection might be irritability, decreased activity and appetite, and apnea (pauses while breathing).

Contact your doctor right away if your baby or child:

• Has breathing difficulty
• Is irritable and cannot or will not take a bottle or breast
• Is younger than 3 months old and has a fever
• Shows signs of dehydration, such as a dry mouth, crying without tears, and less frequent urination (fewer wet diapers)

RSV spreads easily. When someone who is infected coughs or sneezes, virus-containing droplets become airborne. “If you’re standing within six feet of that person, the virus can enter your body through your eyes, nose, or mouth,” says Dr. Michaels.

You can also get RSV by touching something an infected person touched, like a doorknob or a toy, then touching your eyes, nose, or mouth. The virus can last on hard surfaces for many hours.

Virtually everyone gets RSV at least once and sometimes more than once. “Because you don’t develop a perfect immune response, you can get reinfected,” Michaels notes. “The first infection, however, is usually the worst.”

Young children who attend childcare centers or who have siblings in school are at a higher risk of exposure and infection. When kids bring RSV home, parents often get it, too. “For adults, it’s usually no big deal,” says Michaels. “You have a cold, and you don’t really know it’s different from any other rival infection. That’s because one, our airways are bigger, and two, we’ve seen it before.”

But for some babies, children, and adults, RSV can lead to serious lung infection, breathing problems, and hospitalization. “Infants are particularly vulnerable to severe RSV infection in the first two months of life,” Dr. McCulloch notes. Other people who are at risk for developing severe or life-threatening RSV include:

• Premature infants
• Young children born with heart or lung disease
• Children or adults with weakened immune systems due to diseases like cancer or treatment such as chemotherapy
• Children who have neuromuscular disorders, such as muscular dystrophy
• Adults with heart or lung disease
• Older adults, especially those age 65 and up

Your doctor may suspect RSV based on symptoms and the amount of RSV currently circulating in your community.

The process of making a diagnosis begins with a physical exam that typically includes listening to the lungs with a stethoscope to check for wheezing or other abnormal sounds, as well as a simple test to check blood oxygen levels that uses a small device called a pulse oximeter that clips to a finger, says Mayo Clinic.

To make a definitive diagnosis and rule out other respiratory illnesses like the flu or COVID-19, your doctor may order an antigen (rapid) test or a PCR (polymerase chain reaction) test for RSV.

If more severe illness is suspected, your doctor may order imaging tests — such as a chest X-ray or computerized tomography (CT) scan to check the lungs for signs of infection.

For at-home testing, the U.S. Food and Drug Administration (FDA) recently authorized a kit from Labcorp that lets people determine whether they have RSV, COVID-19, or flu by swabbing their noses and sending the sample to a lab for PCR analysis.

Prognosis of RSV

Most of the time an RSV infection goes away on its own in a week or so, but RSV can be serious in infants and older adults. One to 2 out of every 100 children younger than 6 months old with RSV may need to be hospitalized; most improve with supportive care like oxygen and IV fluids and can go home in a few days, according to the CDC.

RSV usually goes away on its own in one to two weeks, the CDC says. People may have symptoms for three to eight days, during which they are usually contagious. But some babies and individuals with weakened immune systems can continue to spread the virus even after they seem to have recovered, for as long as four weeks, the CDC says.

There is no specific treatment for RSV or medicine that shortens the course of the infection.

In the meantime, if you have RSV or are caring for another adult or a child who is infected, there are some steps you can take to ease discomfort:

• For adults, encourage drinking by keeping a supply of water at the bedside. For a baby with RSV, continue nursing or bottle-feeding as usual; suction their noses first to help with breathing.
• Try using a cool mist vaporizer to soothe dry nasal passages (be sure to keep the humidifier clean to prevent the growth of bacteria or mold).
• Apply saline nasal drops to help loosen mucus.
• Adults with fever and children older than six months can take an over-the-counter pain and fever reducer, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). Never give aspirin to children, as it has been linked to a very rare but dangerous condition called Reye’s syndrome.

One or 2 out of every 100 children younger than 6 months with RSV infection may need to be hospitalized, says the CDC. Those who are hospitalized may require IV fluids, oxygen, and rarely, mechanical ventilation.

There are a number of steps you can take to reduce your risk of getting and spreading RSV.

During RSV season (or whenever RSV is circulating at especially high levels in your community), be sure to:

• Wash your hands frequently (for at least 20 seconds) and teach kids the importance of hand-washing. If soap and water isn’t available, use sanitizer with at least 60 percent alcohol.
• Avoid touching your eyes, nose, and mouth and encourage kids to avoid doing this as well.
• Avoid close contact with those who are sick.
• Don’t share or allow kids to share cups, toys, or bottles.
• Clean high-touch surfaces, like doorknobs and countertops, with virus-killing disinfectant.
• Don’t smoke and avoid exposure to secondhand smoke. Babies who are exposed to tobacco smoke (even from close contact with a smoker’s clothing) have a higher risk of getting severe RSV, Michaels notes.
• Consider wearing a face mask when around people you don’t live with, especially in indoor public areas.

For infants at high risk of severe RSV, including babies born very prematurely or who have congenital lung disease or heart defects, doctors use a protective medication called Synagis (palivizumab), which is a monoclonal antibody (an immune system protein that is created in the lab). The drug, which is given as a monthly injection for five months, can help prevent severe RSV infection.

On the horizon is a monoclonal antibody drug called nirsevimab, recently developed by Sanofi and AstraZeneca, that can protect infants against severe RSV for an entire season with just one shot.

Vaccines for RSV

After decades of research, with many setbacks, numerous RSV vaccine contenders are finally getting close to the finish line.

For adults 60 and older, GSK (formerly known as GlaxoSmithKline) announced in the fall of 2022 that its RSV vaccine candidate is more than 80 percent effective against serious illness. A few months earlier, Pfizer reported that its vaccine was more than 85 percent effective against severe disease.

The FDA is reviewing the companies’ clinical-trial data and is expected to announce a decision about approvals in spring 2023.

As for babies, Pfizer said in the fall of 2022 that its RSV vaccine candidate — administered to mothers during pregnancy — is about 80 percent effective against hospitalization in infants under 90 days old, and almost 70 percent effective among those younger than six months. The vaccine received a breakthrough designation from the FDA earlier in the year, according to a press release, which will expedite the approval process.

“Newborns are highly vulnerable to RSV, but vaccines don’t tend to be effective until a baby is at least 2 months old,” McCulloch says. Vaccinating mothers, who can pass the antibodies on to their babies, is a strategy already used with flu and pertussis (whooping cough), she notes.

Most healthy adults and children handle RSV well, but complications can occur if the virus spreads to the lower respiratory tract.

This can result in bronchiolitis (inflammation of the small airways of the lungs) and pneumonia (infection of the lungs). In fact, RSV is the most common cause of bronchiolitis and pneumonia in children younger than 1 year old, says the CDC.

For both children and adults, RSV can also make chronic health problems worse. For example, those with asthma may experience asthma attacks as a result of RSV infection, notes McCulloch.

Adults with congestive heart failure or chronic obstructive pulmonary disease may experience more severe symptoms, or exacerbations, triggered by RSV, she adds.

While some research suggests that having severe RSV as a baby can increase a child’s risk of developing asthma, it’s not clear if the connection is cause and effect. “We don’t know if kids get asthma because they had severe RSV or if it’s because this child, who was going to have asthma, was more at risk of having RSV cause lung disease,” Michaels explains.

RSV is an extremely common infection that can sometimes lead to serious complications. In a typical pre-pandemic year, RSV led to approximately 58,000 hospitalizations in the United States and as many as 500 deaths among children younger than 5 years old.

For individuals 65 and over, RSV typically caused some 177,000 hospitalizations and 14,000 deaths each year, according to the CDC.

RSV is one of more than 200 different viruses behind the common cold. Rhinoviruses, the most common cause of a cold, account for 10 to 40 percent of colds. Different kinds of coronavirus (there are dozens beyond the one linked to COVID-19) can also result in colds.

HealthyChildren.org

This website, from the American Academy of Pediatrics, offers details about RSV in babies, with video and audio that help caregivers know when a child’s breathing signifies a potentially dangerous case of RSV.

Centers for Disease Control and Prevention

The CDC provides details in English and Spanish about RSV symptoms, transmission, and more, including downloadable fact sheets with info on RSV in older adults and children.