Incidence and spread of a new variant of the type B influenza virus among the population of Czechoslovakia. III. Incidence of type B1 strains in 1960 and in the epidemic of 1961.
D003604:Czechoslovakia; D058872:Epidemics; D006801:Humans; D015994:Incidence; D029524:Betainfluenzavirus; D009975:Orthomyxoviridae
INFLUENZA VIRUSES