Cause and Risk Factors for Bird Flu (Avian Flu)

Bird flu is caused by infection with one of the avian influenza viruses. People who handle or have other contact with infected birds (e.g., farm workers) are at increased risk for developing the disease. People who live in or travel to affected areas of the world (e.g., Asia, and parts of Africa and Europe), health care providers in these areas, and household members of infected patients are also at increased risk.

Signs and Symptoms of Bird Flu

The period of time between exposure to the virus and development of symptoms (called the incubation period) is longer for bird flu than for regular flu, from two to as many as 17 days. Symptoms of bird flu vary, depending on which virus caused the infection. Early symptoms include the following:

  • Cough
  • Extreme fatigue
  • Fever (usually higher than 100.4 °F)
  • Headache
  • Malaise (generally feeling unwell)
  • Muscle aches
  • Runny or stuffy nose
  • Sore throat

Avian flu symptoms often also include diarrhea (may be bloody and/or watery), vomiting, and abdominal pain. Chest pain and bleeding from the nose and gums have also been reported. In most bird flu cases, respiratory tract complications (e.g., pneumonia, acute respiratory distress) develop quickly.

Diagnosis of Bird Flu

If avian flu is suspected, diagnostic tests are used to detect the virus and identify the strain. A physical examination, blood tests, and chest x-rays also may be performed.

In a nasopharyngeal culture, a sample of secretions from the nose and throat is taken using a cotton swab, grown in a laboratory setting, and examined under a microscope for the presence of avian influenza virus. This test can be used to detect flu viruses and determine the strain; however, results of the test can take as long as 3 days.

In February 2006, the Food and Drug Administration approved a rapid test to detect bird flu. Because the H5N1 avian influenza virus is so aggressive, it is important to diagnose this disease and begin treatment quickly. Results of the rapid test usually are available within four hours.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 01 Aug 2007

Last Modified: 01 Sep 2015