Sir

An influenza pandemic will occur at some time in the future: having worked on flu viruses since 1959, I am certain of this. If the deadly H5N1 ‘bird flu’ suddenly acquired human transmissibility, while retaining pathogenicity, the resulting pandemic would cause millions of human deaths. If the pandemic were caused by another bird influenza virus, or if the human H2 virus that disappeared in 1968 were to return, humanity would still be in for a bad time.

No ‘pandemic vaccine’ could be stockpiled, because of uncertainty about the virus strain. So what can be done? School closure, quarantine, travel restrictions and so on are unlikely to be more effective than a garden hose in a forest fire.

There are, however, two safe antiviral drugs that are effective against all flu viruses, including H5N1. These are the neuraminidase-inhibitors zanamivir/Relenza and oseltamivir/Tamiflu. (Although my crystallization of flu virus neuraminidase led to the development of these drugs and I have a financial interest in Relenza, I have none in Tamiflu.)

Tamiflu is a small carbocyclic molecule that was rationally designed from a knowledge of the X-ray crystal structure of influenza virus neuraminidase. The virus needs neuraminidase to escape from infected cells and spread through the body. The catalytic site of flu neuraminidase, unlike the variable surface antigens, is conserved by all strains of the virus. Tamiflu was designed to fit precisely in the catalytic site of the enzyme, inhibiting its activity.

To be effective, Tamiflu has to be given before infection, or very soon after flu symptoms appear. The time needed to obtain a prescription is a serious drawback.

Although governments around the world are reported to be stockpiling Tamiflu, their strategies for using it are not clear. Britain is reported to have 14.6 million doses of Tamiflu, enough for a quarter of the population. Australia is reported to have enough to protect 200,000 front-line workers prophylactically during a pandemic: two pills a day for 50 days.

This strategy, I believe, is wrong. A more efficient use would be to have Tamiflu available over the counter in local pharmacies, coupled with a rapid, sensitive and accurate flu diagnostic test. People with flu symptoms could then go immediately to the pharmacy, be rapidly tested to see if the infection is influenza and, if it is positive, be given Tamiflu.

Not only would the infection be curtailed — the person would, on recovery, be immune to reinfection with the same virus.

This procedure could be called ‘aborted-infection immunization’ and should be used in the early stages of a pandemic, when no vaccine is available, or in the inter-pandemic period by those people who do not take the vaccine or who experience vaccine failure.

The neuraminidase inhibitors exist. They do work. Correct use could be achieved through public education. In a pandemic they would alleviate much of the flu victims' misery, reduce economic losses and probably prevent deaths.