Definition

     Bird flu or avian influenza is flu infection in birds. The disease is of concern to humans, who have no immunity against it. The virus that causes this infection in birds can mutate (change) to easily infect humans. Such mutation can start a deadly worldwide epidemic.

Cause

     Historically, avian influenza viruses infected pigs and mixed with pig influenza viruses. The viruses exchanged genetic information, which led to the formation of a new virus. This new virus could then infect humans and easily spread from person to person. Previous flu pandemics (worldwide epidemics) have started this way.

Symptoms

     Symptoms of avian flu infection in humans depend on the particular strain of virus. In case of the H5N1 virus, infection in humans causes more classic flu-like symptoms, which might include:

• Cough (dry or productive)

• Sore throat  

• Fever  > 100.4°F (38°C)

• Difficulty breathing

• Diarrhea

• Runny nose

• Headache

• Malaise

• Muscle aches

Screening and Diagnostics

• Chest x-ray  

• Nasopharyngeal culture  

• Blood differential

• Auscultation (to detect abnormal breath sounds)

     Other tests may be done to look at the functions of your heart, kidneys, and liver.

Treatment 

• Treatment with the antiviral medication oseltamivir (Tamiflu), and perhaps zanamivir (Relenza), may decrease the severity of the disease, if started within 48 hours after symptoms begin. Oseltamivir may also be prescribed for household contacts of people diagnosed with avian flu. Samples of H5N1 from human infections proved resistant to the antiviral medications amantadine and rimantadine. Therefore these medications cannot be used if an H5N1 outbreak occurs.

• People with severe infection may need breathing assistance with mechanical ventilation. It is currently recommended that people diagnosed with H5N1 infection be put in isolation.

• Because different types of avian flu virus may cause different symptoms, treatment may vary.

• Currently, there is no available vaccine against avian influenza. However, a vaccine against H5N1 is being tested in clinical trials.

• Doctors recommend that people get an influenza (flu) shot to reduce the chance of an avian flu virus mixing with a human flu virus, which would create a new virus that may easily spread.

Prognosis

     Prognosis depends on the severity of infection and the type of avian influenza virus that caused it. The current death rate for patients with confirmed H5N1 infection is more than 50%. The H7N7 avian flu outbreak in the Netherlands resulted in 89 confirmed human cases but only one death. An avian flu virus designates H9N2 infected 3 children in Asia; all three recovered.

Complications 

     Pneumonia  and acute respiratory distress are seen with H5N1 infections. Infection with this virus may also lead to sepsis and organ failure.

Prevention  

     Travelers should avoid visits to live-bird markets in areas with an avian flu outbreak. People who work with birds who might be infected should use protective clothing and special breathing masks. Avoiding undercooked or uncooked meat reduces the risk of exposure to avian flu and other food borne diseases.