Bird flu, also called avian influenza, is typically confined to birds, according to the Centers for Disease Control and Prevention (CDC). However, in rare cases, it has crossed over to humans, mainly among humans exposed to infected poultry. Bird flu produces a spectrum of disease in humans ranging from conjunctivitis (inflammation of the lining of the eye) to severe and even fatal pneumonia.
Early Symptoms
Symptoms of avian influenza usually appear within two to five days after exposure to sick or dead poultry, according to National Institutes of Health (NIH) scientist Timothy M. Uyeki. Early symptoms include fever, cough, fatigue, lethargy, muscle pain, headache, sore throat, abdominal pain, nausea, vomiting and diarrhea and are not readily distinguishable from symptoms produced by other kinds of viral infections. In children, the symptoms may include seizures. Conjunctivitis--localized inflammation of the lining of the eye--is a distinctive symptom of avian influenza compared to other kinds of influenza viruses, but it rarely occurs.
Pneumonia
A defining feature of avian influenza is progression to pneumonia. While most kinds of viral infections resolve within four days, according to a 2009 article in "Clinical Infectious Diseases," this is the time when most patients with avian influenza go to the hospital complaining of fever, chills, shortness of breath and chest pain--classic symptoms of pneumonia. In one series, the median age of patients was 20; most had no underlying medical conditions. The mortality rate of avian influenza is more than 60 percent, even with access to medical care. In fatal cases, the average time between onset of symptoms death and is nine days.
Other Complications
Although bird flu exerts its main effects on the lungs, other body systems are also affected. Complications that don't affect the lungs in patients with bird flu include heart failure, kidney failure, encephalitis, multisystem organ failure and clots in the blood vessels (disseminated intravascular coagulation). In a 2008 article in the "New England Journal of Medicine," the authors describe spontaneous abortion in a pregnant woman with bird flu. In many cases, these complications herald death.
References
- Centers for Disease Control and Prevention: Avian Influenza A Virus Infections of Humans
- "Clinical Infectious Diseases;" Human Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus: Review of Clinical Issues; T.M. Uyeki; 2009
- "New England Journal of Medicine;" Update on Avian influenza A (H5N1) Virus Infection in Humans; Writing Committee of the Second World Health Organization Consultation on Clinical Aspects of Human Infection with Avian Influenza A (H5N1) Virus; 2008
