Sunday, March 26, 2006

No frills status summary

For my own purposes I made a quick status summary of where we are in the H5N1 story. This is a no frills account.

As of today 41 countries have reported H5N1 in birds and 9 of these countries in humans (I have added Egypt to WHO's official tally of eight. Four or five dozen bird species and 9 mammals (including humans) have been found naturally infected and a handful more have been infected experimentally. Among the mammals are pigs, cats and dogs, all animals that live closely with humans in many parts of the world.

Thus almost a quarter of the countries with bird infections also have human infections. This is a conservative estimate as many countries with reported bird infections have limited ability to detect human cases. So far none of the seven western European countries with infected birds have reported human cases, although mammalian infections have been reported in Germany and Austria (cats, marten). Human cases have been reported as far westward as Turkey and Iraq. Vietnam has reported the most cases and deaths (93/42, 2003 - present), with Indonesia rapidly coming up in second place (29/22, all since July, 2005).

The virus has crossed species barriers in birds (approximately five dozen species now infected) and in mammals (9 species). It has not been looked for in many other species, so we do not know the full extent of its host range. It has retained its lethality in most species where it has been detected. The age distribution of viral infections continues to show a marked shift to younger age groups compared to the usual seasonal flu age distribution. It is differentiating genetically and continuing to evolve, although the meaning of this in terms of public health is unknown.

Cambodia, China and Indonesia have reported additional human cases in the last few days, so the virus continues to propagate in birds and humans. The official WHO total count as of March 24 is 186 cases of whom 105 have died (56%). The WHO official tally is an undercount and only includes cases where laboratory confirmation has been obtained from a WHO reference laboratory or equivalent.

A year ago this virus seemed bottled up in Asia and Southeast Asia. In July it suddenly became visible in Indonesia, with cases in humans, birds, cats and swine. Since then we have seen a steadily accelerating geographic spread of the disease in birds with sporadic cases in other species, including humans, in other areas. Small clusters of human cases have also been seen, although spread beyond secondary cases is not known to occur at this time.

Clearly there is a lot going on with this virus, only some of which we know and less we understand. It is obviously time to be taking prudent measures to plan for a possible pandemic at some time in the near future. The best time to do this is when we can do it calmly, rationally and efficiently.

If it doesn't happen, that will be great. Anyone who says it couldn't happen or that we needn't be concerned about it yet because it has only killed birds and a handful of people is unbelievably irresponsible. I will name names: Marc Siegel and Peter Doshi.