Editor's note: This page was last updated on Aug. 24, 2023 following the approval of various RSV vaccines and a new preventative, antibody-based drug.

Respiratory syncytial virus, or RSV, is a very common respiratory virus, particularly among children.

Indeed, "by age 2, 90% of people have had at least one infection" with RSV, said Dr. Octavio Ramilo, chief of infectious diseases at Nationwide Children's Hospital in Columbus, Ohio, who studies RSV. But people can catch the virus at any age, and become infected multiple times.

In healthy children and adults, the virus typically causes mild, cold-like symptoms, but it can cause more serious disease in infants younger than 12 months old, or adults over age 65, according to the Centers for Disease Control and Prevention (CDC). In these more serious cases, the virus spreads from the upper respiratory tract to the lungs, potentially leading to pneumonia, inflammation of the lungs' air sacs (alveoli), or bronchiolitis, inflammation of the lungs' small airway passages.

Infants are particularly at risk for severe disease because of their tiny airways — which, when inflamed, can easily compromise breathing — as well as their immature immune system, Ramilo said.

"When you look at the number one cause of hospitalization in the first year of life, the number one is RSV," Ramilo told Live Science. It's a "very problematic pathogen," Ramilo added, and the infection leads to millions of doctor visits and thousands of hospitalizations each year.

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What are the symptoms of RSV?

Symptoms of RSV often resemble those of the common cold. According to the CDC, typical symptoms include:

Runny nose/congestion Coughing Sneezing Fever Decrease in appetite Headache In infants, additional symptoms can include fussiness and poor feeding, according to the American Academy of Pediatrics (AAP).

Symptoms typically appear within four to six days of exposure to the virus, according to the Mayo Clinic. In severe cases, the Mayo Clinic says symptoms can also include:

Wheezing Difficulty breathing or rapid breathing A bluish color of the skin caused by lack of oxygen Severe cough People should seek immediate medical care if they experience difficulty breathing, a high fever or a blueish color of the skin, according to the Mayo Clinic.

How does RSV spread?

RSV can spread through the air when an infected person coughs or sneezes, or through contact with contaminated surfaces. The virus can survive for up to six hours on hard surfaces, such as toys and doorknobs, and can survive for about 30 minutes on unclean hands, according to AAP.

Children often spread the virus to others at school or in daycare settings, according to the CDC. Those who are infected with the virus are typically contagious for three to eight days; but people with an immunodeficiency may be contagious for much longer, up to four weeks and even after symptoms clear up.

Is RSV seasonal?

In the U.S., RSV typically circulates from late fall to early spring, but the exact timing in a given region can vary from year to year, according to the CDC.

The COVID-19 pandemic also disrupted the timing of RSV season, leading to unusual summer outbreaks and earlier-than-average seasons. According to a report published in July 2021 in the CDC journal Morbidity and Mortality Weekly Report, RSV activity in the U.S. dropped to historically low levels from about April 2020 to April 2021. But when COVID-19 restrictions began to lift in the spring of 2021, RSV surged, leading to a summer spike in RSV infections, the report said.

The reason behind these trends still isn't clear, Ramilo said. Although some experts suspect that measures to reduce the spread of COVID-19 taken in 2020, such as mask-wearing and social distancing, also reduced the spread of RSV, Ramilo said he doesn't think this is the whole story. "I don't think we can explain everything from nonpharmaceutical interventions" like masking wearing and social distancing, said Ramilo, who noted that other respiratory viruses, such as rhinovirus and adenovirus, still circulated in 2020, despite restrictions.

What is clear is that the summer of 2021 saw a dramatic increase in RSV hospitalizations. "Here, we saw a big increase in July and August," at the same level that's usually seen in December or January, Ramilo said. In 25 years of studying RSV, "this is the first time we've seen an outbreak in the middle of July and August," he said.

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Is RSV the same as COVID-19?

RSV is different from COVID-19. RSV belongs to a family of viruses known as pneumoviruses, whereas SARS-CoV-2, the virus that causes COVID-19, belongs to a group of viruses known as coronaviruses. Since RSV and SARS-CoV-2 are both respiratory viruses, their symptoms can be similar, according to the Mayo Clinic.

It is possible to be infected with both RSV and COVID-19, but such coinfections do not appear to be common, Ramilo said. Doctors have been on the lookout for these coinfections because it's known that children can sometimes be infected with RSV and other coronaviruses that cause the common cold, Ramilo said. But "we haven't seen very many cases [of RSV and COVID-19 coinfections], just a handful," he said.

What are the risk factors for RSV?

According to the CDC and AAP, people at risk for severe RSV infections include:

Premature babies, particularly those born before 29 weeks Children younger than 2 years old with congenital heart disease or chronic lung disease Children or adults with weakened immune systems due to a medical condition (such as cancer) or medical treatment (such as an organ transplant) Adults older than 65, especially those with chronic heart or lung disease Every year in the U.S., the virus leads to approximately 2.1 million doctor's visits among children younger than 5 and about 58,000 to 80,000 hospitalizations in the same age group, the CDC estimates. It's the most common cause of hospitalization in infants, and annually, 100 to 300 children under 5 die from the infection in the U.S.

Among adults ages 65 and older, RSV leads to 60,000 to 160,000 hospitalizations each year and about 6,000 to 10,000 deaths in the U.S.

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How is RSV treated?

There's no specific treatment for RSV. Because RSV is caused by a virus, not a bacterium, antibiotics won't work to treat the infection. Most people who catch RSV get better within a week or two without medical intervention.

Over-the-counter medicines, such as acetaminophen or ibuprofen, can help manage symptoms, such as pain and fever. Children should never take aspirin, according to the CDC. People can also use nasal saline drops and suctioning to help with a stuffy nose, according to the Mayo Clinic. Those with an infection should drink plenty of fluids to stay hydrated.

RSV may also increase the risk of ear infections in children, according to the AAP. If a child develops a bacterial ear infection, their doctor may prescribe antibiotics.

In rare cases, people with RSV are hospitalized, and their treatment in the hospital may include fluids, additional oxygen or use of a mechanical ventilator to help with breathing.

In the U.S., about 3% of infants with RSV infection need to be hospitalized, Ramilo said. But most are able to go home within two to three days, according to the AAP.

How to prevent RSV spread

Basic hygiene measures can reduce the risk of RSV infection, according to the Mayo Clinic, including:

Frequent hand washing Regular cleaning of frequently-touched surfaces, such as doorknobs, as well as children's toys Covering coughs and sneezes (with your sleeve rather than your hands.) Avoiding contact with sick people People who have cold symptoms should steer clear of those at risk for severe disease from RSV.

Is there a vaccine for RSV?

There are two FDA-approved vaccines for RSV — one for older adults, and one for both older adults and pregnant people.

The FDA approved the first-ever RSV vaccine in May 2023. The shot, called Arexvy and made by the pharmaceutical company GSK, is approved for adults ages 60 and older.

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The vaccine contains an adjuvant, a substance that revs up the immune system, and a lab-made version of a protein found on the surface of the virus. The virus uses this fusion, or "F" protein, to break into cells. The shot trains the immune system to recognize what the F protein looks like in its "prefusion" form, the shape it's in before it infects cells.

The second RSV vaccine approved by the FDA is called Abrysvo. Made by Pfizer, the shot was approved for older adults in May 2023 and for pregnant people in August 2023. Like Arexvy, Abrysvo contains lab-made perfusion F proteins. Neither vaccine contains preservatives, according to their drug labels.

Read more about the vaccines and who should get them.

Are there drugs to prevent RSV?

There are two antibody-based drugs available to protect infants and some young children from RSV.

These injectable drugs, called monoclonal antibodies, are given to infants during their first RSV season. And some older children at high risk of infection are recommended the shots in their second RSV season.

The shots contains lab-made proteins that mimic antibodies made by the immune system. This type of drug doesn't train a child's immune system to make its own RSV-fighting antibodies, like a vaccine would. Instead it provides a ready-made supply.

Read more about the monoclonal antibodies, who should get them and when.

Additional resources

Read more about RSV in infants and children, from the American Academy of Pediatrics. Get more details on RSV symptoms and care, from the CDC. Find information on RSV risks and complications, from the Mayo Clinic.

This article is for informational purposes only, and is not meant to offer medical advice.