NEW YORK, Aug 27 (Reuters) -- Influenza viruses that originate in birds can acquire the ability to recognize and bind to human cells while they are in the respiratory tract of pigs, according to a new report.
The findings support the notion that pigs act as "mixing vessels" that alter avian virus strains so that they can cause pandemics -- worldwide influenza epidemics that can be potentially life-threatening to susceptible individuals. Influenza pandemics occurred in 1918, 1957, 1968 and 1977, according to the report in the September issue of the Journal of Virology.
"These findings help to explain the emergence of pandemic influenza viruses and support the need for continued surveillance of swine for viruses carrying avian virus genes," report Dr. Toshihiro Ito and colleagues from research centers around the world.
Bird viruses are usually 100-fold less efficient at replicating in humans and other primates, although a variety of both human and avian viruses can infect pigs. In the new study, the researchers found that cell receptors in the respiratory tract of pigs bind to both human and avian influenza viruses.
"The evidence we present supports the role of pigs as a source of potentially hazardous influenza A viruses, arising through classical genetic reassortment or a novel adaptation to human virus receptors or perhaps through both mechanisms," the authors conclude. "Thus, continued intensive monitoring of swine populations for avian-like influenza viruses should be an integral part of global health planning."
SOURCE: Journal of Virology 1998;72:7367-7373.
