Rhinovirus

Rhinovirus

Viral disease

Colds are caused by more than two hundred different viruses. The most common groups of viruses are rhinoviruses and coronaviruses.

The virus can be passed in various ways. When an infected person coughs, sneezes, or speaks, for example, fluid droplets containing the virus are discharged. People nearby may breathe in the droplets and may then become infected.

Cold viruses can be passed from person to person through direct contact, such as shaking hands. The viruses can also be spread through nonliving objects, such as doorknobs, telephones, and toys. This method of transmission is common in day-care centers. A child with a cold may transfer the cold virus to a toy with which he or she is playing. When another child picks up the same toy, he or she may also pick up the cold virus.

Most colds are caused by rhinoviruses that are in invisible droplets in the air we breathe or on things we touch. More than 100 different rhinoviruses can infiltrate the protective lining of the nose and throat, triggering an immune system reaction that can cause a throat sore and headache, and make it hard to breathe through the nose.

Air that's dry — indoors or out — can lower resistance to infection by the viruses that cause colds. And so can being a smoker or being around someone who's smoking. People who smoke are more likely to catch a cold than people who don't — and their symptoms will probably be worse, last longer, and are more likely to lead to bronchitis or even pneumonia.