SCIENCE/TECHNOLOGY: Poor states need bird flu funds

Analysis

The epidemic of H5N1 avian influenza in China and South-east Asia remains widespread, both in domestic chickens and ducks and wild birds (see SCIENCE/TECHNOLOGY: Plans needed for flu pandemic - October 28, 2005; and see SCIENCE/TECHNOLOGY: High risk of bird flu pandemic - July 27, 2005). From there, the disease has spread through Central Asia to Europe and Africa, almost certainly carried by wild migratory birds. The forthcoming spring migrations of wild birds from Africa will probably result in many more infected birds arriving in Western Europe. In addition to China and South-east Asia, countries reporting bird flu in domesticated chicken populations include Turkey, Iraq, Nigeria and India. Since the outbreaks in these countries were first detected in their domesticated populations, it is likely that the disease had previously been present and is now widespread among wild birds there, and probably also in neighbouring states.

According to the most recent World Health Organisation (WHO) figures, there have been 92 human deaths from infection with H5N1 avian influenza. All seem to have resulted from intimate contact with infected birds, and as yet there is no documented case of human-to-human transmission. About 50% of those affected have died. Children and young adults, for whom conventional human influenza is rarely fatal, seem particularly vulnerable to this disease.

National responses. For some months, those countries that can afford to, have been preparing for avian influenza in three main ways:

• They have readied their veterinary services to detect, isolate and eradicate any outbreak among wild or domestic birds.
• They have drawn up contingency plans for health and other government services to handle human infections, should a pandemic occur.
• They are ordering stockpiles of vaccine and anti-viral drugs to protect as many as possible of their populations, starting with front-line medical and military personnel.

The United States has led the way, announcing that it would invest 7.1 billion dollars in preparations against an influenza pandemic. While some of this money will be spent stockpiling anti-viral drugs, the majority will be used to create new vaccine production facilities, using state-of-the-art cell culture facilities, that will have the capacity to produce some 600 million doses within six months -- roughly doubling the world's present flu vaccine production capabilities. Many European governments also have placed orders for Tamiflu and other anti-viral drugs. However, because of limited production capacity, these will not be fulfilled for several months. Moreover, an effective vaccine against a human pandemic strain of H5N1 cannot be prepared until this strain emerges. Therefore, only less effective vaccines against the existing avian H5N1 strain are likely to be available -- in limited quantities -- during the first wave of a pandemic.

Viral evolution. It is the nature of viruses such as influenza to change continuously, because of inherent inaccuracies in their genome replication mechanisms. Some of these mutant strains show new properties that enable the virus to replicate more effectively within its vertebrate host, or become more infectious. Two changes in the H5N1 strain recently have been noted:

• In Vietnam, the first signs of drug resistance have been seen to Tamiflu, the major anti-viral drug being stockpiled as the first line of protection against a potential pandemic.
• An isolate of the virus from Turkey, sequenced at the National Institute for Medical Research in the United Kingdom, shows mutations that permit it to bind more effectively to human cells than avian cells.

Such changes are to be expected. The fear is that further mutations will lead to the ability of the virus to infect humans easily and to pass from one human to another, both necessary prerequisites for a human pandemic (see SCIENCE/TECHNOLOGY: Concerns mount over hybrid virus - March 29, 2004).

Control measures. European veterinary services are introducing culling and movement restrictions on poultry in regions where H5N1 has been detected in wild swans. Most are ordering that all domestic flocks be confined indoors, out of potential contact with wild birds. There are also plans to vaccinate poultry in the Netherlands and France.

There is every chance that these measures, if rigorously enforced, will be effective in preventing the disease spreading among domestic poultry flocks. Nonetheless, there may be further falls in the sale of chicken because of perceived risk.

Nigerian risk. The situation is less encouraging elsewhere. For example, in Nigeria the disease is already widespread in domestic chicken flocks and has infected people. Inadequate veterinary expertise, compensation funds and protective clothing will make it extremely difficult to eradicate there. There have been reports of veterinary officers being unwilling fully to impose WHO recommendations because that would cripple the local poultry industry and, in a country where chickens for consumption are often sold alive in markets, people rushing to sell diseased birds before restrictions are imposed. Such behaviour clearly will spread the disease and increase the risk of further human infections, particularly among people whose immune systems may be suppressed as a result of poverty and disease.

International community policies. The chances of the virus mutating to a human pandemic strain are directly proportional to the number of human infections, which are greatest in poorer countries where people live in close contact with their livestock. These countries require immediate, substantial and continuing financial and technical assistance in detecting, containing and eradicating the disease from domestic birds, and changing bird farming practices to reduce the amount of contact both with wild birds and humans.

At a recent meeting in Beijing, international leaders pledged 1.9 billion dollars to combat avian influenza in these poorer countries, of which 162 million is from Europe and 330 million from the United States. With more countries at risk as the avian disease spreads, it is clear that these sums, even if made available immediately, will prove insufficient (see INTERNATIONAL: Bird flu will reduce global GDP - November 10, 2005).