Studies of cholera El Tor in the Philippines. I. Characteristics of cholera El Tor in Negros Occidental Province, November 1961 to September 1962.

After freedom from cholera for over a quarter of a century, the Philippines in 1961 experienced an epidemic of cholera. The disease, shown to be caused by the El Tor strain of cholera vibrio, was clinically indistinguishable from classical Asian cholera. Studies were undertaken in Negros Occidental Province from August to October 1962 to characterize various aspects of the epidemics in this province. This paper describes the general characteristics of the epidemics in Negros Occidental from November 1961 through September 1962.Two types of epidemic occurred. The first, explosive in nature, suggested a common source of spread of infection; the second, with a more protracted course, seemed to be due to person-to-person spread of disease. In the second epidemic, a single hospitalized case in a household and a single hospitalized case in a community were the most common findings, suggesting that infection did not spread easily or, if easily spread, caused significant disease on rare occasions only.