The sound of a hundred shrugging epidemiologists.

New Scientist is being reassuring – sort of – when it declares that this swine flu pandemic business isn’t any kind of surprise:

But in 1998, says Richard Webby of St Jude’s Children’s Research Hospital in Memphis, Tennessee, swine H1N1 hybridised with human and bird viruses, resulting in “triple reassortants” that surfaced in Minnesota, Iowa and Texas. …

By 1999, these viruses comprised the dominant flu strain in North American pigs and, unlike the swine virus they replaced, they were actively evolving. There are many versions with different pig or human surface proteins, including one, like the Mexican flu spreading now, with H1 and N1 from the original swine virus.

…

There are now so many kinds of pig flu that it is no longer seasonal. One in five US pig producers actually makes their own vaccines, says Vincent, as the vaccine industry cannot keep up with the changes.

This rapid evolution posed the “potential for pandemic influenza emergence in North America”, Vincent said last year. Webby, too, warned in 2004 that pigs in the US are “an increasingly important reservoir of viruses with human pandemic potential”. One in five US pig workers has been found to have antibodies to swine flu, showing they have been infected, but most people have no immunity to these viruses.

Kind of puts a damper on that whole bacon thing now, doesn’t it?

Tags: epidemiology