Severe measles in Copenhagen, 1915-1925.

Among the 2,208 cases of measles at the Infectious Disease Hospital of Copenhagen during the period 1915-1925, the case-fatality ratio was 13%. Mortality was significantly higher for secondary cases (those acquired at home) than for index cases; this difference in mortality was independent of family size. Moreover, mortality was higher for secondary cases than for cases acquired in institutions and hospitals. Children infected at day care institutions had the lowest mortality.