Studies of cholera El Tor in the Philippines. 3. Transmission of infection among household contacts of cholera patients.

As part of a broad epidemiological investigation of cholera El Tor in the Philippines, the authors cultured rectal swabs obtained from the household contacts of cholera patients hospitalized in the Negros Occidental Provincial Hospital from August through October 1962. Additional infected persons were found in 25 (60%) of the 42 households with confirmed cases and in 55 (18%) of 302 household contacts of confirmed patients. Since only five of the 55 infected household contacts developed illness severe enough to require hospitalization, it was apparent that those with severe illness accounted for but a small proportion of the total infections. Asymptomatic infections were rarely found outside the households with proven cases, suggesting that close person-to-person contact was necessary for the spread of infection. Asymptomatic carriers as well as symptomatic patients appeared to play significant roles in the transmission of infection.