A poultry problem?
In dealing with avian flu, don't look to SARS for a model.
There are growing fears of an influenza pandemic as avian flu sweeps through poultry stocks across Asia. Already, a dozen people have died as a result of contracting the disease by direct contact with infected birds, and there are fears of millions of deaths worldwide if the disease begins to be transmitted directly from one person to another.
While there is some basis to these fears, they are almost certainly overstated. Avian flu is a major problem for chicken producers in east Asia, but a number of important barriers mean its effect on human health is likely to be relatively small.
The worry about avian flu should be looked at in context. There has been much talk in medical circles of the near-inevitability of another ‘big one’ – a new disease which causes many thousands or millions of deaths in a very short space of time. As Professor John Oxford of Queen Mary’s School of Medicine in London wrote in The Times last year, ‘We virologists are akin to volcanologists – we sit waiting for the explosion, knowing it will come, but not being sure exactly when’ (1).
Influenza, and avian flu in particular, is a prime candidate to be the ‘big one’, having already caused a small outbreak in Hong Kong in 1997. Influenza not only contributes to thousands of deaths each year in Britain alone, but has been responsible for three major pandemics in the past 100 years, most notably the ‘Spanish Flu’ of 1918-19 which may have claimed between 20million and 40million lives. Other pandemics in 1957-58 and 1968-69 claimed many thousands more.
Unlike SARS, the cause of much anxiety last year, influenza can be highly infectious once adapted to a particular species. Avian flu is novel among humans, so there is no built-up resistance. Avian flu appears to have a high mortality rate – at least, in those cases that have been serious enough to be reported. Of 20 cases reported to the World Health Organisation (WHO) up to 5 February, 16 were fatal (2).
The big fear is of a new human strain of influenza emerging as more people are infected with avian flu. WHO notes that ‘If more humans become infected over time, the likelihood also increases that humans, if concurrently infected with human and avian influenza strains, could serve as the “mixing vessel” for the emergence of a novel subtype with sufficient human genes to be easily transmitted from person to person. Such an event would mark the start of an influenza pandemic’ (3).
Precautionary action is already in full swing. Millions of birds are being slaughtered in Thailand, Vietnam, China and other countries. Work is already underway on producing a vaccine.
Exports of uncooked chicken from Thailand, a major exporter, have been banned by the European Union. This move seems excessive given that the press release announcing the move notes that, ‘The EU does not import live poultry and hatching eggs from Thailand and although the risk of importing the virus in meat or meat products is probably very low the Commission wants to make sure that any possible transmission is avoided’ (4).
At present, the reaction to the disease has been relatively restrained, probably because there have been few deaths, and they have almost all been linked back to direct contact with live poultry. While there will be a substantial economic cost to farmers and the poultry industry, there have been no warnings to stay away from certain countries, only advice to avoid contact with live poultry.
However, while the scale of panic about avian flu has been limited, the underlying outlook is precaution. An editorial in The Times (London) captured the mood when it suggested that ‘[A]s SARS showed, however costly the economic consequences, it is better to err on the side of alarmism’ (5).
While there is sense in trying to eliminate the disease from animals as soon as possible, there is a danger of blindly repeating the experience of SARS. The real lesson of SARS was that the reaction was out of all proportion to the threat from the disease. WHO was too quick to issue travel advisories and paint a picture of doom and gloom, such that the resulting economic damage caused far more problems than the disease. Perhaps this explains the ultra-cautious language being used by WHO this time around.
In its present form, avian flu does not represent a major threat to global health. Only those who come into direct contact with live poultry are at risk, and the low number of cases to date suggests that this is not an easy route of transmission. The problems that avian flu cause in Asia, where people are in contact with live poultry in conditions of poverty, need to be dealt with through whatever medical and regulatory means are the best. For those countries with more developed farming conditions, and where human contact with live poultry is minimal, any risk needs to be put into perspective.
If the risks at present are low in east Asia, the virus may have even less impact away from the countries in which they emerge due to such factors as climate, sanitation, poverty and general health. An analogy is with a traveller buying a potted plant while on holiday only to find it wilt and die back home. A virus that emerges in one set of circumstances may simply fail to thrive in a different situation.
For those who do not come into contact with live poultry, there is almost no risk of infection. Transmission from one person to another seems to be extremely inefficient. Even if the worst were to happen and avian flu did become much more infectious, there are good reasons to believe that any new pandemic could be dealt with much more effectively than in the past. These are the positive lessons of SARS.
As WHO notes, ‘The threat from avian influenza is well understood. Unlike SARS, diagnostic tests already exist, as do effective, although costly, antivirals for humans. While it is challenging, research is already well underway on the development of a human vaccine against this strain’ (6).
While antibiotics cannot treat a viral disease like influenza, they can deal with other infections that often cause more problems for influenza sufferers than flu itself. Intensive care improvements mean that the very seriously ill can be nursed through crisis points in their illness where perhaps in the past they would have proved fatal.
We should not lose sight of the fact that most people in the world are now generally healthier, wealthier and better fed than they were in the past, especially in comparison to the immediate aftermath of a global conflict in 1918.
A pandemic of avian flu would be unpleasant, but it is unlikely, and if it happens we have the ability to deal with it. However, we live in an era where the human ability to cope with adversity is denigrated, so any new disease can become the object of panic. Perversely, this fear is particularly strong in the West, where infectious disease is rarely more than an irritation for otherwise healthy people, while in the developing world, malaria, AIDS and even diarrhoea kill millions.
While it makes sense for specialists to worry about exotic new diseases like avian flu, the energies of society would be better served trying to conquer the illnesses we already know.
(1) A mass killer is on the way, and we’re not ready, Professor John Oxford, The Times (London), 28 November 2003
(2) Confirmed Human Cases of Avian Influenza A(H5N1), World Health Organisation, 5 February 2004
(3) Avian influenza – fact sheet, World Health Organisation, 15 January 2004
(4) Commission suspends EU poultry imports from Thailand after avian influenza outbreak, EU Commission, 23 January 2004
(5) Avian pandemic, The Times (London), 2 February 2004
(6) Unprecedented spread of avian influenza requires broad collaboration, World Health Organisation, 27 January 2004
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