Surveillance for low-level malaria.

Due to good detection and control, malaria has reached very low levels in China with the result that existing methods of surveillance, taking blood slides from all fever cases and those with a common cold, are finding very few malaria cases among the millions of persons examined. Passive case detection agents in areas of moderate and low endemicity in Hubei Province, China, were instructed to indicate on the form associated with each slide whether the patient was considered to be a clinical case of malaria (group 1), was thought to have malaria but did not have all the features (group 2), had fever alone and was not thought to be a case of malaria (group 3), or merely had a common cold (group 4). In the low endemic area (slide positivity rate 0.23%), only 5 cases in group 3 and 4 in group 2 were detected per 10,000 examinations. It is recommended that these categories be discontinued in malarious areas of low endemicity, to encourage greater efficiency in detecting cases in groups 1 and 2. In the moderately endemic area, with a slide positivity rate of 4.19%, all categories, including group 4, were considered valuable for detecting malaria cases.