Respiratory Syncytial Virus (RSV) is a common respiratory virus responsible for infections in the lungs and breathing passages. Nearly all children will have been infected with RSV by the time they reach two years of age, often presenting with mild, cold-like symptoms. While it can affect people of all ages, the virus poses a significantly higher risk to vulnerable populations. Infants under one year old and adults over 65 are at increased risk for severe illness. Understanding how this virus moves and how long it remains infectious is necessary for protecting those susceptible to severe outcomes like bronchiolitis and pneumonia.
How the Virus Travels
RSV primarily travels through respiratory droplets expelled when an infected person coughs or sneezes. These large droplets typically travel a short distance before falling, leading to droplet spread, which requires close contact for transmission. The virus is then contracted when these droplets land directly on the mucous membranes of the eyes, nose, or mouth of a nearby individual.
Transmission can also occur indirectly through contaminated surfaces, a route known as fomite spread. The virus can survive for many hours on hard, nonporous surfaces, such as crib rails, tables, and toys. An individual can become infected by touching one of these contaminated objects and then touching their face before washing their hands.
While large droplets and direct contact are considered the main mechanisms of spread, the virus may also be carried by fine aerosols. These tiny airborne particles are generated during routine activities like talking and breathing, allowing the virus to travel farther and remain suspended in the air.
The Contagious Window
The timeline of an RSV infection begins with the incubation period, the time between initial exposure and the onset of symptoms. This period typically ranges from two to eight days, with four to six days being the most common timeframe for symptoms to first appear. A person can become contagious and start shedding the virus even before they begin to feel sick, often a day or two before symptoms develop.
The duration of viral shedding (the time a person is infectious) varies significantly by age and immune status. Most healthy adults and older children are contagious for approximately three to eight days. In these cases, contagiousness usually ends once symptoms have largely resolved.
However, the shedding period is notably prolonged in infants and individuals with weakened immune systems. These vulnerable groups can continue to shed the virus and remain contagious for up to four weeks or even longer.
Reducing the Risk of Spread
The most effective way to limit the spread of RSV involves a combination of behavioral changes and modern medical interventions. Isolation is a primary strategy; symptomatic individuals should stay home from work, school, or daycare to avoid transmitting the virus. If a symptomatic person must be around others, wearing a mask can help contain the respiratory droplets that carry the virus.
Rigorous hand hygiene is a powerful tool against transmission, especially given the virus’s ability to survive on surfaces. Frequent hand washing with soap and water for at least 20 seconds, or using an alcohol-based hand sanitizer, significantly reduces the risk of self-inoculation and fomite spread. Regular cleaning and disinfecting of high-touch surfaces, such as doorknobs, countertops, and shared electronic devices, also helps eliminate the virus from the environment.
Modern preventative measures offer targeted protection for the highest-risk groups. New RSV vaccines are available for older adults (typically those aged 60 and over) and pregnant people. Maternal vaccination allows protective antibodies to pass to the fetus, providing the newborn with passive immunity from birth.
For infants, a long-acting monoclonal antibody, such as nirsevimab, is now recommended for those under eight months old and certain high-risk children up to 24 months. This is not a vaccine but a single injection of lab-made antibodies that immediately provide protection for the RSV season. This prophylactic measure is highly effective, demonstrating a significant reduction in hospitalizations related to severe RSV illness in babies.