AN INFLUENZA-A (H1N1) VIRUS, CLOSELY-RELATED TO SWINE INFLUENZA-VIRUS, RESPONSIBLE FOR A FATAL CASE OF HUMAN INFLUENZA

In July 1991, an influenza A virus, designated A/Maryland/12/91 (A/MD) , was isolated from the bronchial secretions of a 27-year-old animal c aretaker. He had been admitted to the hospital with bilateral pneumoni a and died of acute respiratory distress syndrome 13 days later. Antig enic analyses with postinfection ferret antisera and monoclonal antibo dies to recent H1 swine hemagglutinins indicated that the hemagglutini n of this virus was antigenically related to, but distinguishable from , those of other influenza A (H1N1) viruses currently circulating in s wine. Oligonucleotide mapping of total viral RNAs revealed differences between A/MD and other contemporary swine viruses. However, partial s equencing of each RNA segment of A/MD demonstrated that all segments w ere related to those of currently circulating swine viruses. Sequence analysis of the entire hemagglutinin, nucleoprotein, and matrix genes of A/MD revealed a high level of identity with other contemporary swin e viruses. Our studies on A/MD emphasize that H1N1 viruses in pigs obv iously continue to cross species barriers and infect humans.