An influenza B epidemic within a remote Alaska community. Serologic, epidemiologic, and clinical observations.

During January 1969 an epidmic of influenza B was documented in Klawock, Alaska, a remote insular community 80 miles west of Ketchikan. One person died and 149 others developed an acute respiratory disease characterized by fever, cough, headache, and coryza. A fourfold or greater rise in hemagglutination-inhibiting (HI) antibody titer to influenza B developed in 26 persons, and influenza B virus was isolated from 5 patients. Reciprocal HI testing of the Alaska strain (B/Alaska/4-69) did not disclose a significant antigenic difference from the vaccine strain (B/Massachusetts/3-66). However, 36 of the 46 persons who had been vaccinated during the preceding 3 to 12 months developed clinical influenza, and the attack rate within this group did not differ significantly from the attack rate among the unvaccinated population.