Q: What are the differences between a cold and the flu?

A: The common cold is a mild, viral respiratory illness seen year round, characterized by a cough, scratchy throat, runny nose, headache, and sinus congestion. It usually has no lingering complications once symptoms abate.

By contrast, flu, caused by the influenza virus, comes with more severe and sudden symptoms, such as fever, sore throat, and muscle aches, followed by cough. Serious complications can develop, such as pneumonia, especially in older people.

Both cold and flu symptoms last about a week. If caught early, the flu can be treated with antiviral drugs, but most people will improve without care. Neither antibiotics nor antivirals help a cold. Those symptoms can be relieved by over-the-counter drugs.

December through March is the traditional flu season. Flu can be diagnosed with a nasal or throat swab. If you test positive for flu and your symptoms began within the last 48 hours, your doctor may suggest antivirals to help you recover faster.

If you experience any of these severe symptoms, call your doctor:

Fever lasting more than three days can signal a bacterial infection.

Fever and severe sore throat without coughing can mean strep throat.

Persistent congestion and headaches can be signs of a sinus infection.

An annual vaccine can prevent flu. Within two weeks of getting the vaccine, antibodies are protective. The flu vaccine is changed every year and is recommended yearly for almost everyone, especially for children older than 6 months, pregnant women, adults over 50, and people with chronic illness or suppressed immune systems. Another tool to prevent colds and flu is frequent hand-washing.

- Ronald Goren, M.D.