MOLECULAR-BASIS FOR THE GENERATION IN PIGS OF INFLUENZA-A VIRUSES WITH PANDEMIC POTENTIAL

Genetic and biologic observations suggest that pigs may serve as ''mix ing vessels'' for the generation of human-avian influenza A virus reas sortants, similar to those responsible for the 1957 and 1968 pandemics . Here we demonstrate a structural basis for this hypothesis. Cell sur face receptors for both human and avian influenza viruses were identif ied in the pig trachea, providing a milieu conducive to viral replicat ion and genetic reassortment. Surprisingly, with continued replication , some avian-like swine viruses acquired the ability to recognize huma n virus receptors, raising the possibility of their direct transmissio n to human populations. These findings help to explain the emergence o f pandemic influenza viruses and support the need for continued survei llance of swine for viruses carrying avian virus genes.