Overview

Viruses cause most colds and flu. Viruses spread when uninfected people inhale respiratory droplets put out by the coughing and sneezing of infected people. Or they can spread indirectly, when you touch something with virus droplets on it and then touch your eyes, nose or mouth.

Severe cold symptoms usually last up to a week, but coughing can last for 3 to 4 weeks. Colds in children may last longer - a week to 2 weeks for the main symptoms.

The common cold can be from one of more than 200 different viruses that can cause an infection once they invade the body. The average person gets two to six colds a year.

Influenza, commonly called the flu, is caused by different strains of two types of a single family of viruses - type A and type B - that change characteristics every year. (There is a third type, C, which rarely causes disease in humans.) Different strains appear every year, so one year's immunity isn't completely effective the next year. The flu may last two weeks.

Colds are more common during the winter, but can occur any time. Influenza appears almost only during the winter months in the northern hemisphere.

A bacterial sinus infection, or acute bacterial sinusitis, lasts about 10 to 28 days and usually follows a cold or allergies. Sinusitis means an inflammation of the sinuses, which are the airspaces within the bones of the face. Sinusitis is usually caused by allergies or a viral infection within these spaces, and doesn't require antibiotics. Symptoms lasting beyond 7 to 10 days may be the result of a bacterial infection with a need for antibiotics.

The types of sinusitis are:

• Acute, which lasts for three weeks or less
• Chronic, defined as lasting three months, but can continue for longer - even years
• Recurrent, which is several acute attacks within a year

Prognosis

The common cold doesn't have a cure. Rest, cough drops and over-the-counter drugs may relieve symptoms. Antibiotics don't kill the viruses that cause colds. Most healthy people can recover from colds and influenza on their own. The flu, however, can be very serious for the elderly. A doctor should check older patients carefully if the flu is suspected.

Acute bacterial sinusitis can be treated successfully with antibiotics.

More on Cold, Flu and Sinus

In the Encyclopedia:

This article was reviewed and updated June 2007.