Effects of suspended residual spraying and of imported malaria on malaria control in the USA.

The activities of the National Malaria Eradication Programme, a co-operative campaign inaugurated in July 1947 by the United States Public Health Service and certain State and local health agencies, are outlined. Control operations reached their maximal level in 1948, when 1,364,950 dwellings in 13 "malarious" States were sprayed with residual DDT, and the percentage of mosquito control achieved was 83.2.In 1950, only 2,227 cases of malaria were reported, as compared with 16,203 in 1947 and 9,797 in 1948. But the return of infected servicemen from Korea caused a temporary increase in the incidence in 1951 and 1952, when the totals were 5,600 and 7,023, respectively. In 1953, however, only 559 civilian cases were reported; of the cases appraised, 28 were of local origin, and, of these, at least 24 are known to have been infected in 1952.The Public Health Service ceased active participation in the Programme in 1951, but continued to give technical advice. At the same time, State authorities received Federal support in activating malaria surveillance-and-prevention programmes. More-selective anti-anopheline activities have replaced residual insecticide spraying, which is now carried out in only a few isolated areas. It is believed that these measures have prevented imported malaria from increasing the diminishing incidence of primary indigenous cases in the USA.