Wednesday, March 02, 2005

Keeping track and chasing the numbers

With Xinhuanet (PR China) reporting two additional suspect cases of bird flu in the north of Vietnam, it is perhaps time to step back and take stock. The confusion over whether the the 21 year old man from Thai Binh (case 18) is alive or dead (see update to post here) should remind us that in a rapidly developing situation with multiple sources of information it is hard to keep track of what is going on. That is why we can be grateful that the Center for Infectious Disease Research and Policy at the University of Minnesota (CIDRAP) is doing the heavy lifting for the rest of us. You can find their count here, including a useful comparison with the "official" WHO figures.

Since mid-December 2004, the combined WHO, press and governmental sources, as disambiguated by CIDRAP, show 22 cases and 14 deaths (case fatality of 63%), all (except one Cambodian case) in Vietnam. The "official" figures are 11 cases and 10 deaths (case fatality 91%), representing confirmed human cases according to WHO. Going back to the beginning of the current outbreak in southeast asia (January 2004), there are 65 cases and 46 deaths in the CIDRAP tabulation (case fatality 71%) and 55 cases with 42 deaths in the official account (case fatality 76%).

People will interpret the recent spate of cases differently. WHO is urging calm:
. . . WHO says the latest reports of bird flu in Vietnam are not necessarily alarming.

It's not an alarming situation, said Hans Troedsson, Vietnam's WHO representative. What we see is the end of this outbreak.

Three or four new cases don't mean something has dramatically changed, he said. We could see sporadic cases popping up irregularly. It is very difficult to predict. (AP/AFP via The Star Online [Malaysia])
Maybe. The question is what will signal a real change in the state of affairs. We suggested earlier that an increase in the size of clusters, not necessarily the number of clusters or cases, would be a red flag. If true, this makes it all the more important to conduct thorough investigations of the familial and other clusters that do appear.