Respiratory syncytial virus (RSV) is a common respiratory virus that most people associate with infants, but it causes significant illness in adults too. In the United States alone, RSV leads to roughly 60,000 to 160,000 hospitalizations and 6,000 to 10,000 deaths each year among adults 65 and older. For healthy younger adults, RSV typically feels like a bad cold. For older adults or those with chronic health conditions, it can progress to pneumonia and respiratory failure.
How RSV Infects the Respiratory Tract
RSV spreads through respiratory droplets and contaminated surfaces. When the virus reaches the mucous membranes of your nose, mouth, or eyes, it latches onto the cells lining your airways and begins replicating inside them. Your immune system responds by flooding the area with inflammatory cells and signaling molecules to fight the infection. This battle between the virus and your immune response is what actually causes most of the damage: the airway lining becomes inflamed and swollen, and debris from destroyed cells starts clogging the passages.
In many adults, the infection stays in the upper airways (nose, throat, sinuses) and resolves on its own. But RSV can move deeper into the lungs, causing bronchitis or pneumonia. When this happens, the smaller airways become obstructed with swelling and cellular debris, making it progressively harder to breathe. People who already have compromised lung function from conditions like COPD or asthma are especially vulnerable to this progression, because their airways have less margin before breathing becomes dangerously difficult.
Symptoms and How They Progress
When RSV stays in the upper respiratory tract, it looks and feels identical to any other cold virus: stuffy nose, runny nose, sore throat, cough, low-grade fever, and fatigue. There’s nothing distinctive about these early symptoms that would tip you off that RSV is the cause rather than a rhinovirus or another common bug.
The concern starts when infection spreads to the lower respiratory tract. Nasal congestion deepens into a productive cough with mucus. Wheezing and shortness of breath develop in 70% to 93% of cases involving the lower airways. You may notice that breathing feels labored during normal activities like walking across a room or climbing stairs. In severe cases, oxygen levels drop and the infection can progress to respiratory failure requiring hospitalization.
The incubation period is typically a few days after exposure. Once symptoms appear, you’re generally contagious for 3 to 8 days, though you may start spreading the virus a day or two before symptoms show up. People with weakened immune systems can remain contagious for four weeks or longer, even after they feel better.
Who Is Most at Risk for Severe Illness
Healthy adults under 65 almost always recover from RSV without complications. The virus becomes dangerous when it hits people whose hearts, lungs, or immune systems are already compromised. Adults at the highest risk for severe RSV include those with:
- Chronic lung disease such as COPD, emphysema, asthma, or interstitial lung disease
- Heart conditions including heart failure, coronary artery disease, or congenital heart disease
- Weakened immune systems from medications, cancer treatment, or immune disorders
- Diabetes with complications such as kidney disease, neuropathy, or retinopathy
- Neurologic or neuromuscular conditions that impair coughing or airway clearance
- Severe obesity with a BMI of 40 or higher
- Chronic liver disease, chronic kidney disease, or chronic blood disorders like sickle cell disease
Nursing home residents face elevated risk regardless of their underlying health, partly because of close living quarters and partly because frailty compounds the strain RSV places on the body. Age alone is a major factor: adults 75 and older are considered high-risk even without other conditions.
Bacterial Coinfection: A Hidden Danger
One of the more serious complications of RSV in adults is bacterial coinfection, where bacteria take advantage of the damaged airway lining and establish a secondary infection on top of the virus. Among hospitalized adults with RSV, bacterial pneumonia has been reported in 42% to nearly 80% of cases. The most common culprit is Streptococcus pneumoniae, found in about 24% of coinfections, followed by several other bacterial species.
These dual infections tend to be considerably worse than RSV alone. Hospital stays are longer, and patients with bacterial coinfection are more likely to end up in intensive care. This is one reason that an RSV infection which seems to be improving and then suddenly worsens, with new fever or increasing shortness of breath, warrants prompt medical attention.
How RSV Is Diagnosed
RSV can’t be distinguished from other respiratory viruses based on symptoms alone, so lab testing is needed for a definitive diagnosis. The two main approaches are PCR-based tests and rapid antigen tests. PCR tests (the same type of molecular test widely used during the COVID-19 pandemic) are highly sensitive and considered the gold standard. Rapid antigen tests return results faster but are less sensitive, meaning they can miss some infections. Many clinics and hospitals now use multiplex panels that test for RSV, flu, and COVID-19 simultaneously from a single nasal swab.
Treatment Is Mostly Supportive
There is no widely available antiviral medication that targets RSV in adults. Treatment focuses on managing symptoms and supporting the body while it fights off the infection. For most people, that means rest, fluids, and over-the-counter medications to reduce fever and relieve congestion.
For those who develop lower respiratory tract involvement, treatment may include supplemental oxygen and inhaled medications to open the airways. People with underlying COPD or asthma often need their existing respiratory medications adjusted during an RSV infection. Hospitalized patients with bacterial coinfection receive antibiotics targeting the secondary bacterial pneumonia. In the most severe cases, patients may need mechanical ventilation to support breathing until the infection clears.
RSV Vaccines for Adults
Three RSV vaccines are now licensed for adults 50 and older: Arexvy (GSK), Abrysvo (Pfizer), and mResvia (Moderna). The CDC has no preference among the three, so the choice typically comes down to availability. Two of these vaccines, Abrysvo and mResvia, are also approved for adults ages 18 to 49 who are at increased risk for severe RSV-related lower respiratory illness.
The CDC recommends a single dose of RSV vaccine for all adults 75 and older and for adults 50 to 74 who have any of the conditions that increase risk of severe disease. This is not an annual shot: one dose is currently considered a complete vaccination, and no booster is recommended at this time. The best timing is late summer or early fall, before RSV season picks up in the community, though eligible adults can get vaccinated at any point during the year.
RSV circulates primarily during fall and winter in most of the United States, following a seasonal pattern similar to the flu. Unlike flu, however, RSV has historically received far less public attention, which means many adults at risk have never discussed vaccination with a healthcare provider. If you’re 75 or older, or between 50 and 74 with a chronic heart, lung, or immune condition, RSV vaccination is a straightforward way to reduce your odds of a serious respiratory illness.