The seventh pandemic of cholera in the USSR, 1961-89.

Over the period 1961-89 a total of 1,713,057 cases of cholera were reported to WHO from 117 countries in all continents. The course of the epidemic fell into three periods: in period I (1961 to 1969), 24 countries (predominantly in Asia) reported about 419,968 cholera cases; in period II (1970 to 1977), 73 countries from Asia, Africa, Europe, and the Americas reported 706,261 cases; and in period III (1978 to 1989), 83 countries reported 586,828 cases. The global epidemic was at its most severe in 1967-74. Subsequently morbidity declined and up to 1989 had remained high and stable, with 44,000-52,000 cases per annum. In the USSR 10,723 cholera cases and carriers were reported between 1965 and 1989 from 11 republics (but not Latvia, Lithuania, Estonia, or Armenia). In 1965 and 1970-74 large-scale outbreaks of imported cholera were characteristic of the epidemic in the USSR. Thereafter morbidity declined, and sporadic cases were reported along with environmental, predominantly nontoxigenic strains of cholera vibrio. Most of the outbreaks in the 1970s were waterborne, and virulent strains containing the vct-gene were isolated from samples of water. Large-scale outbreaks continued that were associated with seafood and dairy produce that were contaminated with cholera vibrio. Clinical cases of cholera as well as a considerable number of carriers of avirulent nontoxigenic strains were reported. The epidemiological situation in the USSR is unstable, with cases of cholera and virulent strains from surface water being reported every year.(ABSTRACT TRUNCATED AT 250 WORDS)