Henan Province (population, 90 million) in China has nonstable endemic malaria. After 1970 when 10.2 million cases of malaria were reported in the province, a huge control programme was undertaken, and in the mid-1980s indoor spraying and bednet impregnation with pyrethroids began. By 1992 only 318 cases were reported. In 1992 Henan declared "basic elimination of malaria" and in consequence spraying and bednet impregnation ceased after 1994. Subsequently, malaria broke out again in southern Henan. In 1995 we conducted a household survey for malaria transmission in southern Henan. Blood smears and serum samples for immunofluorescent antibody (IFA) testing were collected from 2329 people and 3.1% (73/2329) were positive for infection with Plasmodium vivax and 13% (301/2329) positive for malaria (titre > or = 1:20). All age groups were affected. Exophilic Anopheles sinensis occurs throughout the province; endo-anthropophilic A. anthropophagus, whose vectorial capacity is 20 times greater than that of A. sinensis, occurs mainly in southern Henan (S of latitude 33 degrees N) and was greatly reduced in numbers during 1985-92. Comparison of 1995 entomological data with historical data showed that A. anthropophagus increased in proportion to other anophelines after spraying activities and impregnation of bednets ceased. Over 10% of 9377 residents reported having malaria. The true number affected among the at-risk population of 700,000 must be larger. We conclude that impregnated bednets and malaria surveillance should continue even after an area is declared to have "basically eliminated" malaria.
PIP: As a result of an aggressive malaria control program initiated in China's Henan Province in 1970, including indoor spraying and bednet impregnation with pyrethroids, the "basic elimination of malaria" was declared in 1992 and spraying and bednet impregnation ceased in 1994. Subsequently, there was a resurgence of vivax malaria in southern Henan. In a 1995 household survey of malaria transmission in three counties in southern Henan, blood smears and serum samples were collected for immunofluorescent antibody testing from 2329 residents. 3.1% were positive for infection with Plasmodium vivax and 13% were positive for malaria (titre of 1:20 and above). More than 10% of 9377 residents in six counties reported having malaria at least once in 1994-95. Comparison of 1995 entomological data with historical data indicated that Anopheles anthropophagus increased in proportion to other anophelines after spraying activities and bednet impregnation ceased. Malaria control in Henan should not have led to withdrawal of protective measures, especially since there is extensive cross-border movement in this area.