H1N1: The Hidden or Concealed Pandemic

H1N1 swine flu continues to roam the planet. In the US, cases are thought to be in the hundreds of thousands. In Japan, hundreds of teenagers have caught it, despite no obvious connections with Mexico or the US.

Yet in Europe, health authorities are not testing widely for it and are prescribing drugs as though they could still contain it. And in Geneva, health ministers have fought this week to keep the World Health Organization from following its own rules and calling this a pandemic.

There has been a phenomenal mismatch between quite sensible rules about how to declare a flu pandemic, and equally sensible rules about how to respond. The mismatch was wholly predictable, yet somehow no one saw this coming.

The WHO rules for declaring different degrees of flu pandemic threat are based on epidemiology (how the virus is spreading) for good reasons. This is because any new flu virus to which most of the world has little immunity, and which spreads well enough person-to-person to escape its continent of origin, is very likely to go global, and to cause more sickness and death than flu usually does. That is the definition of a flu pandemic.

The virus's ability to spread is what matters. H5N1 bird flu has travelled across Eurasia, mainly in birds, but it hasn't spread readily in people, so it isn't a pandemic.

The Mexican swine flu H1N1, however, has. When it spread across the Americas, the WHO followed its rules and declared it a level 5 situation; one down from a pandemic. When it starts spreading outside the Americas, through "community transmission" - meaning it crops up generally, not just in people who have visited Mexico or New York recently or their contacts - that means it's got a foothold globally.

A flu that can do that is very unlikely to stop there. The WHO rules make that a full-blown level 6 pandemic.

And frankly, that is starting to happen. As I write, the number of confirmed cases in Japan (and that's just people sick enough to see a doctor and get tested) has jumped by 35 in the past 24 hours, to nearly 300, mostly due to that perennial vector of flu, the gregarious teenager. The main cluster started without any known links to the Americas.

In Europe, countries are deliberately not testing cases that could be community acquired, almost as if someone doesn't want to trigger - 'LEVEL 6'

In fact, Britain, Japan and other countries spent this past week pleading with the WHO not to go to level 6 yet, at least while the virus is still causing mostly mild disease. WHO boss Margaret Chan has now agreed to make the call when she sees "more signals coming from the virus itself or the spread of the disease, including severity."

The problem is, countries have pandemic plans that, rightly, prepare for the worst. Until recently we were worried about H5N1 (we still are) and there seemed a good chance that if it went pandemic, it might start off severe, necessitating major controls from the start.