MOSQUITO-TRANSMITTED MALARIA IN NEW-YORK-CITY, 1993

In August, 1993, 3 cases of Plasmodium falciparum malaria in people wi thout recent travel histories or bloodborne exposure were reported in New York City. An epidemiological investigation confirmed the absence of risk factors for acquisition of malaria in two cases. The third cas e could not be definitively classified as locally acquired malaria bec ause the patient had travelled to Thailand two years before malaria wa s diagnosed. The 3 individuals lived in separate houses in the same ne ighbourhood of Queens, New York and had onset of illness within a day of each other. The investigation consisted of patient interviews, acti ve case finding, reviewing recent New York flight and shipping arrival s, and an entomological survey for anopheline mosquitoes and breeding sites. No other cases were identified. The 3 patients lived several mi les from air and sea ports and prevailing winds would have carried any mosquitoes at those sites away from the patients' homes. By the time of the environmental investigation (September, 1993), the area was dry and neither adult nor larval anophelines were found. However, weather conditions at the probable time of infection (July, 1993) were very d ifferent.Malaria was probably transmitted to these 2 patients by local anopheline mosquitoes that had fed on infected human hosts. Mosquito- control measures were not implemented because there was no evidence of ongoing transmission. The occurrence of mosquito-transmitted malaria in New York City demonstrates the potential for reintroduction of mala ria transmission into areas that are no longer endemic and emphasises the need for continued surveillance and prompt investigations, if case s without risk factors are reported.