Swine influenza A at Fort Dix, New Jersey (January-February 1976). I. Case finding and clinical study of cases.

After the isolation of A/New Jersey/76 (Hsw1N1) influenza virus from five soldiers at Fort Dix, New Jersey, case finding was initiated by obtaining specimens for viral isolation from 95 patients with acute respiratory disease and determining antibody to influenza A/Mayo Clinic/103/74 (Hsw1N1) antigen in paired sera from 74 soldiers who had been hospitalized with acute respiratory disease. Influenza A/New Jersey virus was not isolated, but serologic studies identified eight additional soldiers as A/New Jersey influenza patients. Development of heterotypic antibody to A/Mayo Clinic antigen following infection and/or immunization with influenza A (H3N2) strains was studied and was found to occur infrequently. One of the 13 identified patients had died, and postmortem findings were consistent with viral pneumonia. Four of the 12 surviving patients had radiologic evidence of pneumonia, but clinical syndromes in all 12 were similar to those described for other influenza A infections.

Swine influenza A at Fort Dix, New Jersey (January-February 1976). II. Transmission and morbidity in units with cases.

Epidemiologic study of 13 influenza A/New Jersey/76 (Hsw1N1) patients indicated that person-to-person transmission had occurred in several distinct military units. Soldiers in eight of these units (companies) were studied to determine whether they had experienced influenza A/New Jersey infections and associated acute respiratory disease. Titers of hemagglutination-inhibiting antibody to influenza A/Mayo Clinic/103/74 (Hsw1n1) antigen were determined. In seven of these eight companies, individuals with titers of greater than or equal to 1:20 were found. In these seven companies, members of platoons with cases (contact platoons) had antibody prevalences of 7%-56%, and members of platoons without cases had prevalences of 0-40%. Hospital admissions for acute respiratory disease were proportionately greater in trainees with A/Mayo Clinic antibody titers of greater than or equal to 1:20 than in trainees without antibody in five of six contact platoons studied.