Typical symptoms resemble the common cold. However, RSV infection can also result in pneumonia, especially in the very young, the very old or those with weakened immune systems. However, mild or inapparent illness may occur. Symptoms may persist for a few days to a number of weeks. Symptoms generally begin four to six days after exposure.
Symptoms generally develop slowly over a period of several days.
The contagious period is usually less than 10 days after symptoms begin, but occasionally is longer. RSV is usually diagnosed based upon the appearance of typical symptoms. The use of specific laboratory tests is often limited to cases of severe illness and to special outbreak investigations. A medication called ribavirin is effective against RSV infection if begun in the first few days after symptoms appear. Because RSV infection is often resolved on its own, treatment of mild symptoms is not necessary for most people.