Avian Influenza: Exploring All the Avenues

As the clock continues to tick, health officials worldwide are scrambling to find viable means to head off the next pandemic. To date (9 August 2006), 236 recognized cases of avian (H5N1) influenza virus infections have occurred in humans, resulting in 138 deaths. New human cases are now being detected in Thailand after initial hope that the disease had been controlled there. The vast majority of these cases have been the result of transmission directly to humans from infected birds, although person-to-person transmission has occurred in a few instances. The potential for these avian viruses to completely bridge the species barrier and acquire the ability to spread between humans is unclear; recent experiments suggest that adaptation to mammals may be complex (1). However, if this virus, or some other influenza virus with a novel hemagglutinin or neuraminidase, does emerge as a human-to-human pathogen at some point, the world will confront an extremely severe public health threat.

Our options for combating an H5N1 pandemic are limited. Vaccines will represent the ultimate method of control but, given the limits of current vaccine production technology, may not be available in time to prevent the first wave of pandemic cases. In addition, for reasons that are not clear, effective immunization using conventional inactivated vaccines will require relatively high doses, which will reduce vaccine availability during a pandemic (2, 3). Antiviral agents have some …