Bird Flu (Avian Influenza, H5N1, H7N9)

Bird Flu Summary
The H5N1 and H7N9 influenza A strains cause bird flu in humans. Bird flu symptoms include typical flu-like symptoms. People may also experience vomiting, nausea, and diarrhea. The antiviral medications oseltamivir and zanamivir may be effective against bird flu complications.
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Bird flu (avian influenza) facts

  • Bird flu is a viral infection of birds that infrequently, to date, may infect humans.
  • Bird flu in humans is caused by influenza A strains of viruses (H5N1 and H7N9).
  • The greatest risk factor for getting bird flu is close contact with sick or dead birds.
  • Seek medical care immediately if infection with bird flu is suspected.
  • Currently, person-to-person transfer of bird flu is rare.
  • In humans, bird flu causes fever, cough, sore throat, and muscle aches, and some have nausea, vomiting, diarrhea, or eye infections; about 60% develop serious complications and die.
  • Presumptive diagnosis is done by symptoms and known association with infected or dead birds; definitive diagnosis is done by specialized lab tests.
  • Treatment for bird flu is antiviral drugs and supportive care, usually done in a hospital.
  • There are no known effective home remedies for bird flu.
  • Complications of bird flu are common and include respiratory, heart, kidney, and other organ system damage that often results in death.
  • In general, the prognosis is poor for bird flu as only about 40% of infected people survive.
  • Avoiding areas where bird flu is having a breakout and staying away from sick or dead birds is the best way to prevent the infection.
  • There is no commercially available bird flu vaccine. The U.S. government has some vaccine against H5N1 strains, and the NIH is testing another vaccine against strain H7N9, but these are not available to the public in 2013.
  • There is controversy about experimental manipulation of bird flu to make it more easily transferrable (more infectious) in humans.

What is bird flu?

Bird flu (also termed avian influenza) is a viral-caused illness that affects wild and domesticated birds. The disease usually causes either little or no symptoms unless the bird population is susceptible, in which it may cause death in birds within about 48 hours. Influenza A virus strains that cause bird flu primarily affect birds and are not easily able to infect people. However, in the late 1990s, a new strain of bird flu arose that was remarkable for its ability to cause severe disease and death in domesticated birds such as ducks, chickens, or turkeys. This strain was called "highly pathogenic" (meaning very severe) avian influenza (HPAI, a term seen in older publications).

Known history of humans affected by bird flu is short. The first human case of illness from highly pathogenic avian influenza was identified in 1997, and about 641 infected people have been identified by October 2013, mainly infected by strain H5N1 with 380 deaths. Human infection with bird flu is rare but frequently fatal. More than half of those people infected (380) have died (a current estimate of the mortality rates in humans is about 60%). The Chinese government announced they detected a new strain of bird flu in March 2013. It is named H7N9 (also termed H7N9 Chinese bird flu). The WHO has been informed by Chinese officials of a total of 136 laboratory-confirmed human cases with avian influenza A (H7N9) virus infection, including 45 deaths, but the figures vary according to the source. So far, there is no evidence of sustainable human-to-human transmission, but Chinese officials in October 2013 reported the first incident of person-to-person transmission of H7N9 bird flu although all other people infected had direct contact with infected birds (chickens). H7N9 is transmitted from person to person although this situation is being closely watched for any changes. The H7N9 strain has been detected mainly in China (Shanghai and several other smaller cities), and the patients usually come from areas where they have a likelihood of direct contact with infected birds. Other big cities in China (Beijing, Hong Kong) have not reported infections to date. The WHO (World Health Organization) in April 2013 started publishing daily updates on the H7N9 infections and deaths reported in China.

Birds have been affected with avian influenza in Asia, Europe, the Near East, and Africa, and the outbreak has killed millions of poultry. In October 2013, an outbreak in Australia resulted in the culling (destruction) of about 400,000 chickens to prevent further spread of the H7N9 strain. Highly pathogenic bird flu strain(s) are not currently found in the United States. Human cases of bird flu have largely been confined to Southeast Asia and Africa. The virus spreads from bird to bird as infected birds shed flu virus in their saliva, nasal secretions, and droppings. Healthy birds get infected when they come into contact with contaminated secretions or feces from infected birds. Contaminated surfaces such as cages might also allow the virus to transfer from bird to bird. Contact with humans occurs in the same way, mainly by flocks of chickens cultivated by farmers who are exposed to wild birds infected with bird flu viruses. Other people are exposed to the bird flu when, for example, infected birds are processed for sale before they are cooked or if people come in contact with contaminated wild bird droppings or dead birds.

Medically Reviewed by a Doctor on 1/10/2014