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Key Bird Flu questions answered.This web page aims to provide you with the answers you've been looking for relating to the current bird flu threat. This information is drawn from the most respected sources from around the world so you can be sure that what you read on this web page will help you to develop a clearer picture of the current situation relating to bird flu. Click on a link below to find out more: What
is bird flu? Why
is there so much concern about the current outbreaks of bird flu?
Can
a bird flu pandemic be averted? How
long does it take for for humans to develop symptoms of bird flu? How
severe is the illness caused by bird flu? What
are the symptoms associated with bird flu? Would
my flu shot protect me against bird flu? Is
there a vaccine effective against bird flu (H5N1) in humans? Will
normal seasonal influenza vaccine protect me against bird flu? Are
presently available vaccines useful in averting a bird flu pandemic? Are
any drugs available for prevention and treatment for bird flu? Should
my doctor prescribe antiviral drugs for travel to affected areas?
Is
it true that some countries are stockpiling an H5N1 bird flu vaccine?
What
measures can I take now to prepare for a bird flu pandemic?What is bird flu?Bird flu is a disease of birds caused by influenza viruses closely related to human influenza viruses. It is an important disease economically for poultry farmers because of losses in poultry flocks. Transmission to humans in close contact with poultry or other birds occurs rarely and only with some strains of Bird Flu. The potential for transformation of Bird Flu into a form that both causes severe disease in humans and spreads easily from person to person is a great concern for world health.Why is there so much concern about the current outbreaks of bird flu?Public health officials are alarmed by the unprecedented outbreaks of bird flu in poultry for several reasons. First, most – but not all – of the major outbreaks recently reported in Asia have been caused by the highly pathogenic H5N1 strain. There is mounting evidence that this strain has a unique capacity to jump the species barrier and cause severe disease, with high mortality, in humans.A second and even greater concern is the possibility that the present situation could give rise to another influenza global epidemic (a pandemic) in humans. Scientists know that avian and human influenza viruses can exchange genes when a person is simultaneously infected with viruses from both species. This process of gene swapping inside the human body can give rise to a completely new subtype of the influenza virus to which few, if any, humans would have natural immunity. Moreover, existing vaccines, which are developed each year to match presently circulating strains and protect humans during seasonal epidemics, would not be effective against a completely new bird flu virus. If the new bird flu virus contains sufficient human genes, transmission directly from one person to another (instead of from birds to humans only) can occur. When this happens, the conditions for the start of a new influenza pandemic will have been met. Most alarming would be a situation in which person-to-person transmission resulted in successive generations of severe disease with high mortality. This was the situation during the great influenza pandemic of 1918–1919, when a completely new influenza virus subtype emerged and spread around the globe, in around 4 to 6 months. Several waves of infection occurred over 2 years, killing an estimated 40–50 million persons. Can a bird flu pandemic be averted?No one knows for sure. Influenza viruses are highly unstable and their behavior defies prediction. However, WHO believes that if the right actions are taken quickly, a bird flu pandemic might be averted. This is WHO’s foremost objective at present.The first priority, and the major line of defence, 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 emergency introduction of control measures, including the destruction all infected or exposed poultry stock, and the proper disposal of carcasses. All available evidence points to an increased risk of transmission of bird flu to humans when outbreaks of highly pathogenic avian H5N1 influenza are widespread in poultry. As the number of human infections grows, the risk increases that a new virus subtype could emerge, triggering a bird flu pandemic. This link between widespread infection in poultry and increased risk of human infection is being demonstrated right now in Asia. All but one of the human cases and deaths detected since 2004 have been detected in two countries – Vietnam and Thailand – with very widespread outbreaks in poultry. WHO stresses the urgency of the situation and the need for rapid
action in the animal and agricultural sectors. For example, the culling
in 1997 of Hong Kong’s entire bird population – an estimated
1.5 million chickens and other birds – was done in 3 days. Again
in 2003, the culling of nearly 30 million birds (out of a total bird
population of 100 million) in the Netherlands was done within a week.
Rapid action in both of these situations is thought by many influenza
experts to have averted a bird
flu pandemic in humans. How long does it take for for humans to develop symptoms of bird flu after infection?The time from exposure to the source of infection to onset of bird flu is likely to be between three and five days, with a maximum time of seven days.How severe is the illness caused by bird flu?This appears to vary. In the Hong Kong outbreak of bird flu (subtype H5N1) infection in 1997 there were 18 human cases and six deaths. In the Netherlands outbreak caused by H7N7 avian influenza there were 88 cases with minor symptoms like conjunctivitis (eye infection) and one death. In the current outbreak in southeast and east Asia (caused by H5N1) human illness is very severe in most reported cases. Some cases have been reported to have fully recovered; other cases have reportedly died with pneumonia. Factors underlying severity of illness are not well understood.What are the symptoms associated with bird flu?Early symptoms in humans are likely to be similar to normal influenza such as fever and cough.Would my flu shot protect me against bird flu?Your usual annual flu vaccination will not provide any protection
against bird flu. A new vaccine would need to be produced for
this new strain of flu. Is there a vaccine effective against bird flu (H5N1) in humans?No. Currently available vaccines will not protect against disease caused by the H5N1 strain in humans. WHO is urgently working together with laboratories in the WHO Global Influenza Surveillance Network to develop a prototype H5N1 virus for use by leading vaccine manufacturers.Various organisations worldwide are working towards producing a vaccine against bird flu (H5N1) including the National Institute for Biological Standards and Control (NIBSC) in the UK. Some organisations and some manufacturers have produced candidate vaccines which can be evaluated in humans. However mass production of a vaccine will not take place unless there is evidence of efficient spread between humans. Will normal seasonal influenza vaccine protect me against bird flu?The normal seasonal influenza vaccine provides protection against currently circulating strains of human influenza. It does not provide protection against bird flu H5N1.In the event of a bird flu pandemic, an appropriate vaccine will be developed and made available. The UK Government's Department of Health has invited manufacturers to tender for a contract to supply a limited amount of H5N1 vaccine. The move is part of the work to prepare for and reduce the impact of a possible flu pandemic. Are presently available vaccines useful in averting a bird flu pandemic?Not really, except when used in a very precisely targeted way. Current vaccines, when administered to groups such as poultry cullers, protect against circulating human strains and thus reduce the risk that humans at high risk of exposure to the bird virus might become infected with human and avian viruses at the same time. Such dual infections give the avian and human viruses an opportunity to exchange genes, possibly resulting in a new bird flu subtype with pandemic potential.Annual vaccines are produced for routine use in protecting humans during seasonal epidemics of influenza. They offer no protection against infection with the H5N1 bird flu virus. For these reasons, WHO has issued guidelines for the vaccination, using the current trivalent influenza vaccine, of groups considered at high risk of exposure in countries experiencing outbreaks of highly pathogenic H5N1 bird flu in poultry. Are any drugs available for prevention and treatment for bird flu?Yes. While two classes of drugs are available (The M2 inhibitors - amantadine and rimantadine - and the neuraminidase inhibitors - oseltamivir and zanimivir) initial analysis of viruses isolated from the recently fatal cases in Viet Nam indicates that the viruses are invariably resistant to the M2 inhibitors. Oseltamivir has however been demonstrated under laboratory conditions to be effective against the current H5N1 strains. Most experts agree that neuraminidase inhibitors will be vitally important in managing the consequences of a future bird flu pandemic. The UK government is taking steps to ensure these will be available.Should I ask my doctor to prescribe influenza antiviral drugs if I am going to an area where bird flu outbreaks are occurring?To date, there have been no cases of confirmed influenza A (H5N1) infection in travelers returning from these regions. Transmission of bird flu to those visiting a country affected by highly pathogenic bird flu (HPAI) is highly unlikely if you abide by the travel advice posted on the Department of Health and NaTHNaC websites.
Until the bird flu pandemic starts, it is difficult to predict what
strain of influenza will cause it. Predictions may prove to be wrong
or the predicted virus may have changed enough for a pre-prepared
vaccine to be ineffective. |
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