Avian influenza is caused by bird flu viruses that occur naturally among birds. Wild birds carry the viruses in their intestines, but usually do not get sick from them. However, the viruses become deadly and contagious when they infect domestic birds, including chickens, ducks, and turkeys. During an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.
Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe to acute respiratory diseases and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.
 Mode of Transmission
Infected birds shed influenza virus in their saliva, nasal secretions, and feces. Susceptible birds become infected when they have contact with contaminated secretions or excretions or with surfaces that are contaminated with secretions or excretions from infected birds. Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.
Human-to-human transmission of bird flu has happened about a dozen times in the past, in countries including Cambodia, Thailand, Vietnam and Indonesia. In nearly every case, transmission has occurred among blood relatives who have been in close contact, and the virus has not spread into the wider community.
 Did You Know?
- People believe that during a Bird Flu outbreak, they will get the disease by eating eggs, chicken and other poultry. But this is not strictly true -- if the eggs and the meat are cooked through, there is no danger of contracting Bird Flu in this way.
- In 1957, the Asian flu from the H2N2 influenza virus killed 100,000 people.
- Highly pathogenic avian influenza, with a mortality rate approaching 100%, was first recognized in Italy in 1878. 
- According to WHO, the first strain of H5N1 was in Scotland in 1959. Since this time there have been approximately 20 more outbreaks. 
- It was first isolated from birds (terns) in South Africa in 1961. This was an H5N3 strain. 
- During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. 
- Only two large “die -offs” of birds have occurred - once in South Africa in 1961 and most recently Hong Kong during the 2002-2003 winter. 
- The first known human infection was in Hong Kong in 1997. 
- The only U.S. avian flu outbreak to date was a strain of H5N2 in Pennsylvania in 1983.
 Human Health Risks During a Bird Flu Outbreak
 High Risk Group
- Household or close family contacts of a strongly suspected or confirmed H5N1 patient, because of potential exposure to a common environmental or poultry source as well as exposure to the index case.
 Moderate Risk Group
- Personnel involved in handling sick animals or decontaminating affected environments (including animal disposal) if personal protective equipment may not have been used properly.
- Individuals with unprotected and very close direct exposure to sick or dead animals infected with the H5N1 virus or to particular birds that have been directly implicated in human cases.
- Health care personnel in close contact with strongly suspected or confirmed H5N1 patients, for example during intubation or performing tracheal suctioning, or delivering nebulised drugs, or handling inadequately screened/sealed body fluids without any or with insufficient personal protective equipment. This group also includes laboratory personnel who might have an unprotected exposure to virus-containing samples.
 Low Risk Group
- Health care workers not in close contact (distance greater than 1 meter) with a strongly suspected or confirmed H5N1 patient and having no direct contact with infectious material from that patient.
- Health care workers who used appropriate personal protective equipment during exposure to H5N1 patients.
- Personnel involved in culling non-infected or likely non-infected animal populations as a control measure.
- Personnel involved in handling sick animals or decontaminating affected environments (including animal disposal), who used proper personal protective equipment
 Bird Flu Treatment
The World Health Organization recommends the use of neuraminidase inhibitors principally oseltamivir with zanamivir as a less recommended alternative. Neuraminidase inhibitors work by inhibiting the ability of the virus to reproduce. If neuraminidase inhibitors are not available then amantadine or rimantadine can be used, but they are not generally as effective. These drugs also work by inhibiting the virus' ability to reproduce. These drugs can also be used for chemoprophylaxis, but regard should be paid to supply levels to ensure that these are sufficient to treat those actually infected with the H5N1 virus. There are no global guidelines on the use of antibiotics either as treatment or prophylaxis as there is too much variance in resistance patterns in the virus from region to region. Antibiotics should be considered for any secondary infections such as ventilator-associated or hospital-acquired pneumonia.
 Is Culling of Birds During an Outbreak the Solution?
- Human to Human Transmission of Bird Flu
- Center for Disease Control and Prevention
- WHO Rapid Advice Guidelines on pharmacological management of humans infected with avian influenza A (H5N1) virus