Sporadic occurrence of zoonotic swine influenza virus infections.

Two infections by swine influenza virus, antigenically similar to A/New Jersey/76 (H1N1) virus, were detected during community epidemics with other influenza viruses. The swinelike viruses were obtained during virological surveillance of acute respiratory illnesses, and the clinical symptoms of these two patients were similar to those caused by other respiratory viruses. Both patients reported contact with swine a few days before onset of illness, but in one case it was brief. Serological studies suggested that one patient may have transmitted the virus to his roommate, but spread into the community was not indicated.