Tuesday, September 20, 2005

Bird flu conventional wisdom?

As a wise person once said, "It's not what I don't know that scares me. It's what I think I know and I'm wrong about." The current H5N1 outbreak in Indonesia requires we look at our conventional wisdom about transmission and presentation of this disease. In an electronic version of the Clinicians Biosecurity Network Weekly Bulletin yesterday (9/19/05), Borio and Bartlett reviewed a recent article in the Journal of Infectious Diseases (J Infect Dis. 2005 Oct 15;192(8):1311-4) by Frederick Hayden and Alice Croisier. Several points are made.

Conventional wisdom is that transmission of influenza is primarily human-to-human via respiratory droplets, with possibly some transmission via hands (handshakes, etc.) or inanimate objects with viable virus on them. But with many reports of viral particles in bird feces and in one case at least in human feces, the possibility of the fecal - oral route must be considered. This means the gastrointestinal tract is a route of exposure, consistent with reports of infection by consumption of undercooked poultry.If the virus can infect the human intestine (as it does the intestines of birds), then the persistent reports of diarrhea being a common presenting symptom must be clearly recognized, not as a rare presentation but a relatively common one.

The JID article also reports that a WHO study done this year shows that 30% of the Vietnamese cases do not give a history of contact with infected poultry. This suggests, once again, that there might already be much undetected human-to-human transmission of relatively mild disease in southeast asia. We have already made this point a number of times. The absence of any systematic seroprevalence surveys in the area is to be deplored. We should know the answer to this question by now.

In past pandemics there have usually been several waves, the first of which is often milder, with the second the most severe. If it is true that we may have already experienced a mild wave in southeast asia last spring, this bodes ill for the coming months. While it is quite possible that the Indonesian episode is a false alarm, alarm is now appropriate, false or otherwise. Time is getting short for individual communities to mobilize and organize themselves to minimize the consequences of what potentially is a much more serious threat than Hurricane Katrina. This is a warning of a global hurricane. And we are no more prepared than were the authorities in New Orleans.