Patterns of respiratory illness among elderly persons: the value of communitywide surveillance studies for influenza.
Poland
G A
GA
D000368:Aged; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D008297:Male; D008403:Mass Screening; D012107:Research Design; D012111:Residence Characteristics; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000821:virology*