Avian influenza, known more casually as bird flu, is an infectious disease caused by a family of viruses that normally infect birds. Beginning in 1997 an avian influenza called H5N1 has infected and caused the deaths of humans.
Causes and symptoms
An influenza virus that birds carry in their intestines causes Avian flu. The virus spreads as infected birds excrete saliva, nasal secretions, and feces. Birds vulnerable to the flu become infected when they come into contact with the excretions or surfaces contaminated by the viruses.
Birds that survive the H5N1 infection can excrete the virus for at least 10 days. This has helped the H5N1 strain to spread through bird-to-bird contact from wild birds to domestic birds on farms in live bird markets. The virus can also spread in surfaces including manure, bird feed, equipment, vehicles, egg flats, and crates, and the clothing and shoes of people who come into contact with the virus.
In general, people who contract bird flu have symptoms similar to traditional human influenza including fever, cough, sore throat, and aching muscles. Other symptoms included eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications. Influenza weakens the respiratory system and leaves the lungs open to infection. Many people with flu die from a pneumonia caused by secondary bacterial infection. Bacteria are able to grow in the lungs because the body's defenses have been weakened by the flu virus.
Diagnosis
The symptoms of avian flu and human flu are very similar, so laboratory testing is needed to diagnose avian influenza. In addition to diagnosing the individual, testing in 2005 was performed to determine whether the infection was spreading from birds to people or from humans to humans.
Diagnostic tests for human flu are rapid and reliable, according to WHO. International laboratories within WHO's global network have high-security facilities and experienced staff to test samples of suspected avian flu sent from around the world. Test methods include a viral culture that analyses a blood sample and swabbings of the nose or throat. Other testing examines respiratory secretions.
In the United States, the Centers for Disease Control is among the organizations preparing for a possible outbreak of bird flu in humans. In addition to specifics related to diagnosing bird flu, CDC refers healthcare workers to precautions to prevent the spread of flu and other respiratory infections in medical settings.
Precautionary measures include restricting bird from coming into the United States from infected countries, testing poultry for avian flu viruses and euthanizing infected birds. People with symptoms of respiratory infection are advised to cover their mouths or use facial tissues when coughing or sneezing. After coughing or sneezing, individuals should wash their hands well with soap and water, alcohol-based hand rub, or antiseptic handwash.
In July 2007, The United States Food and Drug Administration approved the first vaccine for use against H5N1 bird flu. The vaccine will be administered in two injections about 30 days apart. It will not be available to individuals, but has been purchased by the United States government to be distributed through the public health system in the event that the H5N1 virus develops the ability to pass from person to person.
Treatment with existing drugs
Existing anti-viral drugs may be partially effective against avian flu viruses if they are administered promptly. In the United States, four drugs have been approved by the U.S. Food and Drug Administration (FDA) for the treatment and prevention of influenza A viruses. Amantadine (Symmetrel), rimantadine (Flumadine), seltamivir (Tamiflu), and zanamivir (Relenza) have proven clinically effective in the treatment of human influenza A viruses in otherwise healthy adults.
However, avian flu research indicated that the H5N1 virus was resistant to amantadine and rimantadine, according to CDC. The other two drugs would "probably work," according to CDC. However effectiveness has not bee proven.
Prognosis
Bird flu has been fatal to fewer than 200 people as of mid-2007. Health organizations and government agencies focused on preventing or reducing the risks of a pandemic caused by bird flu.
Prevention
As of 2007, bird flu was primarily a risk for people in the United States who worked with poultry. Potentially vulnerable people included those working with poultry on farms, processing plants, and avian veterinarians. People working with birds in locations such as commercial poultry facilities, veterinary offices, and live bird markets should wear protective clothing. That equipment includes boots, coveralls, face masks, gloves, and headgear, according to the United States Department of Agriculture (USDA).
Furthermore, poultry producers should implement security measures to prevent the outbreak of a highly pathogenic virus. Those actions include keeping flocks away from wild or migratory birds and providing clothing and disinfectant facilities for employees. Plastic crates are recommended for use at live bird markets because they are easier to clean than wood crates. Cleaning and disinfecting areas are also important for preventing an outbreak. Infected birds will be quarantined or destroyed.