AVIAN INFLUENZA (H5N1) - Frequently asked questions

What is avian influenza?
Avian influenza, or "bird flu", is a contagious disease caused by influenza viruses that normally infect only birds, but occasionally also other animals. Domestic poultry is especially vulnerable to infections. It can cause large outbreaks associated with high mortality. In these instances the term “highly pathogenic avian influenza” (HPAI) is used. Outbreaks in poultry may spread rapidly.

What is A(H5N1)?
A(H5N1) is a highly pathogenic strain of bird flu virus that is currently causing epizootics among poultry in South East Asia, and has been detected in Croatia, Russia, Romania and Turkey. The diagnosis can only be made by laboratory tests and must be confirmed in one of the international reference laboratories where the virus is further characterized. Characterisation can take up to two weeks, which therefore could also be the time needed to confirm the disease as being caused by the highly pathogenic avian influenza A(H5N1) virus.

What do the A, the H and the N in A(H5N1) stand for?
Influenza viruses are divided in three types: A, B, and C. Type A viruses infect mammals (among which humans) and birds. Type B and C viruses infect humans only. Type A and B viruses cause the so called “flu”. Type C viruses cause milder respiratory symptoms. Type A influenza viruses are further subdivided into 16 hemagglutinin subtypes (H1-H16) and 9 neuraminidase subtypes (N1-N9). For further information (click here).

What is the risk for the general public?
The risk for people is very small. The A(H5N1) virus that has been circulating since 1997 in Asia, is very aggressive, but does not transmit easily from animal to humans. To date (January 2006) 151 human cases have been reported (in Cambodia, China, Indonesia, Thailand, Turkey and Viet Nam), and all were in very close contact with infected poultry. Of them 82 died. For up-to-date numbers click here. Fortunately, the present virus does not transmit easily from person-to-person.
The threat of the A(H5N1) virus to the general public comes from the following mechanism. First, the A(H5N1) virus may recombine with a human influenza virus. This process of gene reassortment inside the human body can give rise to a completely new subtype of the influenza virus. This can also take place in pigs as pigs can be infected with human as well as avian influenza viruses. Second, the A(H5N1) virus may adapt directly to the human host. In both instances, few, if any, humans would have natural immunity to this new influenza virus.
The worst-case scenario is that this new virus will be easily transmitted from person-to-person and will have a high mortality. This new virus could be capable of infecting many people and could cause a worldwide epidemic (pandemic) with serious consequences. Therefore, the World Health Organization, the European Commission, the European Centre for Disease Prevention and Control and national authorities, are all actively involved in the prevention of transmission from infected animals to humans. In addition, there is a close collaboration between those people specialised in Human and Animal health.

Is there a vaccine against H5N1 in humans?
No. Currently available vaccines will not protect against disease caused by the A(H5N1) strain in humans. The WHO and many other organisations worldwide are working towards producing a vaccine against avian A(H5N1) influenza. Candidate vaccines have been produced, which are being evaluated in humans. However mass production of a vaccine will probably not take place unless there is evidence of efficient spread between humans.

Will normal seasonal influenza vaccine protect me against avian influenza?
The normal seasonal influenza vaccine provides protection against currently circulating strains of human influenza. It does not provide protection against avian influenza A(H5N1). In the event of an influenza pandemic, a new vaccine would need to be produced.

Are drugs available for prevention (prophylaxis) and treatment?
Two licensed modern virus inhibitors (neuraminidase inhibitors) exist: oseltamivir (Tamiflu®) and zanamivir (Relenza®) exist. Both have demonstrated, under laboratory conditions, to be effective against the current A(H5N1) virus. They reduce spreading of the virus and help to diminish the symptoms of influenza. In many European countries the national government already have a stock of these drugs and have placed orders to ensure sufficient quantities.

Can I go on holiday to the affected areas?
There is no negative travel advice for the affected countries due to the bird flu. But people are recommended to stay away from poultry markets and animal farms for children.

How did the avian flu spread from Asia to Europe?
The disease can spread from country to country through international trade in live poultry. The current opinion is that migratory birds could possibly carry the virus for long distances. Their role in spreading of low pathogenic avian influenza is confirmed, but their role in the spread of Highly Pathogenic Avian Influenza A(H5N1) is less clear. Wild ducks are the natural reservoir of bird flu viruses. These birds develop only mild and short-lived illness themselves. They could carry the virus over great distances, and excrete it in their droppings, as such spreading the virus to other areas. Chickens, domestic ducks, turkeys, geese, and several other species raised on farms are susceptible to this virus that causes lethal infections.
Another way Highly Pathogenic Avian Influenza can be spread is by the movement of commercially kept birds, movements of waste products of birds, by contaminated clothes of people moving from farm to farm and by smuggling of infected birds. This is why bio-security is so important.

Can a pandemic be averted?
No one knows for sure. Influenza viruses are highly unstable and their behaviour cannot be predicted. The most important part of prevention is to reduce opportunities for human exposure to the largest reservoir of the virus: infected poultry. This is achieved through the rapid detection of poultry outbreaks and the introduction of emergency control measures, including the destruction of all infected or exposed poultry stock, and the proper disposal of carcasses. The rapid culling of all infected poultry, as happened in Hong Kong in 1997 [A(H5N1)] and in the Netherlands in 2003 [A(H7N7)], is thought by many influenza experts to have averted an influenza pandemic in humans. In the current situation, the focus is therefore on rapid intervention in infected poultry farms, together with proper protection measures for the people in close contact with the infected animals.

For more information see:
http://www.eiss.org/html/influenza_h5n1.html

Last updated: 30 January 2006