Most infants are exposed to the respiratory syncytial virus (RSV) by their second birthday. RSV can cause a serious lung infection in infants and younger children and is more common in premature babies and infants or younger children with health problems, such as heart or lung disease.
Seniors and adults with heart or lung problems may experience a severe infection. People with a weakened immune system are also at risk. RSV does not cause such a serious infection for healthy children and adults, who may experience symptoms that are similar to the common cold.
Even though people, including infants, develop antibodies (immune defenses) against the virus after an infection, it appears the virus is able to reinfect individuals throughout their lifetime. In cases of reinfection, symptoms are usually less severe than the first infection.
Viruses are biological agents made of genetic materials and proteins that are able to infect a host (a living organism) and replicate. RSV can enter the body through the eyes, nose, or mouth. Physical contact, kissing, or inhaling air droplets containing the virus (from an infected person's cough or sneeze) all increase the possibility of acquiring the infection.
The virus particles can live for hours on surfaces such as keyboards, toys, and doorknobs, so you can also become infected by touching your eyes, nose, or mouth after coming into contact with an infected surface.
Much like the flu, which is also caused by a virus, RSV is a seasonal condition. RSV appears to spread most rapidly from autumn to spring. As children enter daycare or interact with other children, RSV moves easily from one child to the next.