Avian influenza, or "bird flu," is a contagious disease of animals caused by viruses that normally infect only birds, and less commonly, pigs. Avian influenza viruses are highly species specific, but have, on rare occasions, crossed the species barrier to infect humans.
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What is special about the current outbreaks in poultry?
The current outbreaks of avian influenza, which began in Southeast Asia in mid-2003, are the largest and most severe on record. Never before have so many countries been simultaneously affected, resulting in the death or destruction of 150 million birds. The causative agent, the H5N1 virus, has proved to be especially tenacious.
What are the implications for human health?
The widespread persistence of H5N1 in poultry populations could lead to direct infection when the virus passes from poultry to humans, resulting in very severe disease. Of the few avian influenza viruses that have crossed the species barrier to infect humans, H5N1 has caused the largest number of cases of severe disease and death in humans. Unlike normal seasonal influenza, where infection causes only mild respiratory symptoms in most people, the disease caused by H5N1 is unusually aggressive, with rapid deterioration and high fatality. Of greater concern is the risk that the virus could mutate into a form that is highly infectious for humans. Such a change could mark the start of a global outbreak.
Does the virus spread easily from birds to humans?
No. Though more than 100 human cases have occurred in the current outbreak, this is a small number compared with the huge number of birds affected and the numerous opportunities for human exposure, especially in areas where backyard flocks are common. It is not presently understood why some people, and not others, become infected following similar exposures.
What about the pandemic risk?
A pandemic can start when three conditions have been met: a new influenza virus subtype emerges; it infects humans, causing serious illness; and it spreads easily and sustainably among humans. The H5N1 virus amply meets the first two conditions: It is a new virus for humans (H5N1 viruses have never circulated widely among people), and it has infected more than 100 humans, killing more than half of them. No one will have immunity should an H5N1-like pandemic virus emerge.
How serious is the current pandemic risk?
The risk of pandemic influenza is serious. With the H5N1 virus now firmly entrenched in large parts of Asia, the risk persists that more human cases will occur. Each additional human case gives the virus an opportunity to improve its transmissibility in humans. The recent spread of the virus to poultry and wild birds in new areas further broadens opportunities for human cases to occur. While neither the timing nor the severity of the next pandemic can be predicted, the probability that a pandemic will occur has increased.
Is the world adequately prepared?
No. Despite an advance warning that has lasted almost two years, the world is ill-prepared to defend itself during a pandemic. The World Health Organization has urged all countries to develop preparedness plans, but only around 40 have done so. WHO has further urged countries with adequate resources to stockpile antiviral drugs nationally for use at the start of a pandemic. Around 30 countries are purchasing large quantities but the manufacturer has no capacity to fill these orders immediately. On present trends, most developing countries will have no access to vaccines and antiviral drugs throughout the duration of a pandemic.
We have a small flock of chickens. Is it safe to keep them?
Yes. In the United States there is no need at present to remove a flock of chickens because of concerns regarding avian influenza. The U.S. Department of Agriculture monitors potential infection of poultry and poultry products.
What precautions can be taken to reduce the risk for infection from wild birds in the United States?
As a general rule, the public should observe wildlife, including wild birds, from a distance. This protects you from possible exposure to pathogens and minimizes disturbance to the animal. Avoid touching wildlife. If there is contact with wildlife do not rub eyes, eat, drink or smoke before washing hands with soap and water. Do not pick up diseased or dead wildlife. Contact your state, tribal or federal natural resource agency if a sick or dead animal is found.
Sources: World Health Organization, Centers for Disease Control and Prevention
