Deceptive calm at global pandemic war's nerve centre

London: An unremarkable low-rise complex of buildings near New Haw in Surrey is in the vanguard of global efforts to monitor and combat avian influenza.

The sprawl of buildings around the original 1917 veterinary laboratory forms the hub of a network of 16 centres run by the Veterinary Laboratories Agency, an executive agency of the Department for Environment, Food and Rural Affairs (Defra).

New Haw hosts the national reference laboratory for avian flu, the reference laboratory for the World Organisation for Animal Health (known by the French acronym OIE) and also for the UN's Food and Agriculture Organisation.

Steve Edwards, chief executive of the VLA, said millions of tests are carried out each year by 1,300 staff to protect animal and human health.

"When emergencies arise, we are ready and we are flexible," he said. If avian flu takes hold in Britain, ongoing work and research would be dropped to focus on influenza.

"When there is a national disease emergency, we have the capacity and the capability to put the resources behind it."

Samples

The lab is testing samples from dead birds collected around the country, as well as confirming results from other labs around the world.

The effort to identify strains is led by Dr Ian Brown, head of avian virology. In a specially equipped laboratory he demonstrates how the first step is to infect chicken eggs with the suspect virus, which comes in the form of a tissue sample, droppings or a cloacal swab (from the backside) because the virus infects the gut of birds.

The scientists drill into the live egg and inject the virus sample into the cavity around the bird embryo, then seal the shell with nail varnish. The cells in the cavity are particularly receptive to growing virus. The egg is incubated for six days, then fluid is extracted. The first simple test is so-called haemagglutinin inhibition. Bird viruses are able to bind to red blood cells and, when added to chicken blood, form a mat of red cells. However, this mat can be created by more than bird flu, notably by what are called ortho- and para-myxoviruses.

When specific reagents antisera are added to the tube, the cells converge to a dot, confirming which H type of virus is there.

If the infected embryos die quickly, in as little as two days, then it might be one of the highly lethal strains such as H5N1 and more tests are required.

The eggs are handled in a glovebox in "category three" facilities, where the laboratory can only be reached by passing through several chambers, held at negative air pressure to ensure that any airborne virus stays inside.

To work there, staff put on special clothes that are washed and sterilised after use.

Deadly flavours of avian flu virus

The avian flu virus subtypes are labelled according to an H number (for haemagglutinin) and an N number (for neuraminidase), referring to the two proteins on its surface.

The H protein helps the virus invade the cells in the throat (in humans in birds it is the digestive tract), while N allows viral progeny to chop their way out of infected cells, the latter being the target for proven treatments such as Tamiflu.

There are 16 flavours of H and nine Ns, giving a possible 144 possible flu strains that they test for. Only three avian strains have made it to humans: H1N1, H2N2, and H3N2. And there is H5N1, the focus of current fears.

The Telegraph Group Limited, London 2006