"Bird Flu"

       In October 2003, an epidemic of influenza in chickens began sweeping through several countries in the Pacific Rim (Vietnam, Thailand, Japan, China, South Korea, Cambodia). The virus is H5N1. The H5 molecule is common among bird influenza viruses but has not been seen on flu viruses that cause human epidemics. However, sporadic human cases of H5N1 (with an alarmingly-high fatality rate) have been occurring ever since. 
        As a glance at the tables above will show, humans have had long experience with infections and vaccines by both H1 and H3 flu viruses. But the human population has absolutely no immunity against any H5 viruses. Has the ground been prepared for another worldwide pandemic? 
         So far, person-to-person spread seems to account for only a few cases. Most cases seem to have been acquired from close contact with infected birds. 
However, there are reports that the virus has been found in pigs. This is very troubling as simultaneous infection of a pig by a human strain could provide the opportunity for genetic reassortment between the two strains [Link] with the creation of an H5 virus able to spread rapidly between humans. 
           Work is going forward on an H5N1 vaccine. However, this is a virus that kills chickens so it is not surprising that it does not grow well in the eggs used for vaccine production