What is bird (avian) flu?

Bird flu is an infection caused by avian (bird) influenza (flu) viruses. These flu viruses occur naturally among birds. Wild birds worldwide, acting as reservoirs, carry a normally harmless form of influenza viruses in their intestines, and wild birds usually do not get sick from them. Unlike most avian influenza viruses, however, the new strain, H5N1, has caused mortality in more than 80 species of wild birds. Avian influenza can be very contagious among domestic poultry, and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.

Do avian influenza viruses infect humans?

Avian influenza (bird flu) viruses do not usually infect humans, but a number of confirmed cases of human infection with bird flu viruses have occurred since 1997, usually in persons who had close contact with infected poultry. One bird flu virus strain known as avian influenza A (H5N1) has been of particular concern in recent years. The World Health Organization (WHO) maintains situation updates and cumulative reports of human cases of avian influenza A (H5N1). This information is available at http://pandemicflu.gov/#map. Additional information is available at http://www.cdc.gov/flu/avian/gen-info/avian-flu-humans.htm.

How do people become infected with bird flu viruses?

Most cases of H5N1 avian influenza infection in humans have resulted from direct or close contact with infected poultry (e.g., domesticated chickens, ducks, and turkeys) or surfaces possibly contaminated from feces of infected birds. For a human influenza pandemic to occur, avian influenza must mutate/change to be able to be passed easily from person to person. A human influenza pandemic can arise from changes that occur in certain kinds of bird flu viruses but no one knows when, or even if, this will happen. Today, there have been no reported cases of sustained human-to-human transmission of bird flu.

What are the symptoms of bird flu in humans?

People infected with the current strain of the avian influenza virus (H5N1) have shown everything from typical human influenza-like symptoms (fever, cough, sore throat, and muscle aches) to pneumonia, severe respiratory distress, and other life-threatening complications.

What areas of the world have bird flu?

The H5N1 strain of avian influenza virus has not infected birds in North or South America to this date. Outbreaks in birds, mainly migratory birds and domestic poultry, have been observed in certain countries in Asia, Europe, and northern and central Africa. For a complete list of countries, visit WHO's Global and Country Maps.

How does avian flu differ from seasonal flu?

Unlike seasonal flu, in which infection usually causes only mild to moderate respiratory symptoms in most people, H5N1 infection may follow an unusually aggressive clinical course, with rapid deterioration and high fatality. Primary viral pneumonia and multi-organ failure have been common among people who have become ill with H5N1 influenza.

In the current situation in Asia, Europe, and Africa, more than half of the people infected with the virus have died. Most cases have occurred in previously healthy children and young adults. However, it is possible that the only cases currently being reported are those in the most severely ill people and that the full range of illness caused by the H5N1 virus has not yet been defined.

Is there a vaccine against bird flu?

No vaccine is currently available. A vaccine is being developed and tested but has not yet been approved for human distribution.

Does the current seasonal flu vaccine protect against bird flu?

No. Influenza vaccine for the 2006-07 season does not provide protection against avian influenza.

What drugs are available for treatment of either seasonal flu or bird flu?

Two drugs, oseltamivir (commercially known as Tamiflu ®), and zanamivir (commercially known as Relenza ®) can reduce the severity and duration of illness caused by seasonal influenza. The effectiveness of the drugs depends on their early administration (within 48 hours after symptom onset). For cases of human infection with H5N1, the drugs may improve prospects of survival, if administered early, but clinical data is limited.

For the above drugs, the main constraints — which are substantial — involve limited production capacity and a price that is prohibitively high for many countries. At present manufacturing capacity, which has recently quadrupled, it will take a decade to produce enough oseltamivir to treat 20% of the world's population. The manufacturing process for oseltamivir is complex and time-consuming, and is not easily transferred to other facilities.

So far, most fatal cases of H5N1 infection have resulted from the effects of the virus and cannot be treated with antibiotics. Nonetheless, since influenza is often complicated by secondary bacterial infection of the lungs, antibiotics could be life saving in the case of late-onset pneumonia.

What is the difference between a vaccine and an antiviral?

Vaccines are usually given as a preventive measure. When immunized, the body is then poised to fight or prevent infection more effectively.

Antivirals are drugs that may be given to help prevent viral infections or to treat people who have been infected by a virus. When given to treat people who have been infected, antiviral medications may help limit the impact of some symptoms and reduce the potential for serious complications, especially for people who are in high risk groups.