[Ecologic dynamics of infectious diseases. I. Seasonal variations]

We studied the incidence of typhoid fever, hepatitis, poliomyelitis, scarlet fever, pertussis and measles from 1954 to 1984 as reported in the yearly records of diseases subjected to compulsory notification. Autocorrelation functions and Fourier analysis were used to study incidence fluctuation. Seasonal variations related in all cases to pathogenic factors were found for all diseases. Air borne transmission was related to a peak incidence in spring and enteric transmission in summer. Person to person transmission and crowding at school are noted as factors influencing the incidence pattern of hepatitis and scarlet fever.