"Calling" a pandemic

A doctor from Quang Ninh who died April 3 after rapid development of Acute Respiratory Distress Syndrome (ARDS) is being investigated as a possible H5N1 case. Also in the differential is SARS, which has been prominently mentioned but seems unlikely. The doctor had no certain contact with bird flu patients, although three H5N1 patients were treated at the hospital where he worked in a different ward. He is the third health care worker suspected of contracting bird flu from patients. The first was confirmed as H5N1, the second was reported "negative" for H5N1 but many people (ourselves included) have doubts about the accuracy of this. And this case, which has yet to be definitively diagnosed.

The significance of health worker cases is that they are a red flag for person to person transmission. This case, in particular, where the contact was not direct and obvious, would be worrisome. Henry Niman at Recombinomics has gone as far as to say that we now have evidence that "[t]he flu pandemic of 2005 has clearly begun." In another post, Niman says:

Although test results have not been released, four cases at the same hospital over a short time frame create a geographical cluster in Quang Ninh. Since these are the only four cases reported in the province, yet are all at Vietnam-Sweden Hospital, the suspicion level is extremely high. It coincides with the executive order in the United States authorizing quarantine of bird flu patients.

I have been asked what I think about this. I am by nature fairly cautious and have a tendency to wait a bit until events sort themselves out. That is a matter of temperament, not facts. On the other hand, it is certainly plausible that Niman has guessed right. Only history will tell. In this case a matter of a few days or a week will make little difference. If there is a pandemic underway, the die is cast and we can't turn the ship around quickly enough. As I and others have been arguing for months, we should be acting as if a pandemic is underway, and these latest reports do nothing to change that basic attitude.

My personal judgment, posted last Sunday, is that there has likely been widespread person to person transmission of relatively mild disease going undetected for some time. While I can make a reasonable supporting argument for this, it is still a guess at this point because the necessary seroprevalence studies have not been done. If this is the case we will have to see if the disease increases in virulence like the "second wave" of the 1918 flu. If this happens we can expect the hammer to come down in August or September. There is thus still time to prepare organizationally for many sick people and mechanisms to limit spread. The antiviral or vaccine moves are already lost.