Swine influenza virus infections. Transmission from ill pigs to humans at a Wisconsin agricultural fair and subsequent probable person-to-person transmission
D. L. Wells, D. J. Hopfensperger, N. H. Arden, M. W. Harmon, J. P. Davis, M. A. Tipple and L. B. Schonberger
Division of Viral and Rickettsial Diseases, Centers for Disease Control, Atlanta, Ga 30333.
In September 1988, a previously healthy 32-year-old pregnant woman was
hospitalized for pneumonia and died 8 days later. The only pathogen
detected was an influenza virus antigenically related to the swine
influenza virus (SIV). Four days before illness onset, the patient visited
a county fair swine exhibition where there was widespread influenzalike
illness among the swine. To detect other persons who were possibly infected
by contact with the ill swine, we measured serum SIV
hemagglutination-inhibition antibody titer in 25 swine exhibitors who were
9 to 19 years old. Nineteen (76%) had SIV hemagglutination-inhibition
titers of 20 or greater. Antibody was undetectable in serum samples from 25
swine exhibitors from a neighboring county. Additional studies suggest that
one to three health care personnel who had contact with the patient
developed influenzalike illnesses with laboratory evidence of SIV
infection. An outbreak of apparent SIV infection in swine resulted in
multiple human infections, and, although no recognized community outbreak
resulted, there was evidence of virus transmission from the patient to
health care personnel.
