The Hong Kong influenza virus epidemic in the USSR.

An epidemic wave of influenza associated with the A2/Hong Kong/68 virus reached the USSR in the second 10-day period of December 1968. During the first quarter of 1969 the epidemic involved almost all cities of the Soviet Union. The intensities of the rise and of the fall of the 1969 epidemic wave were less pronounced than those of the 1965 influenza A2 epidemic, but were more extended. In most towns the epidemic lasted 50-80 days whereas in 1965 the epidemic in towns lasted 25-30 days.The influenza caused by A2/Hong Kong/68 was characterized by an unusual age-group distribution. Children under 7 years of age made up only one-quarter of the total influenza cases during the peak of the epidemic wave in most communities. The clinical course of the disease was, in the main, of average severity, there being no significant differences in symptoms compared with influenza caused by virus A2.Analysing the influenza epidemics associated with influenza A2 virus during recent years one may note peculiar features of the A2 Hong Kong/68 influenza epidemic. On the one hand, these are apparently connected with the shifts in antigenic character of the virus, and, on the other hand, with the timely arrangements undertaken by public health services to prepare for the influenza epidemic, i.e., the carrying out of prophy actic and anti-epidemic measures.