Malaria surveillance in New York City: 1991-1996.
BACKGROUND: The transmission of malaria has increased in recent years in many countries where it was once eradicated or under control, and malaria remains a major cause of morbidity and mortality throughout the developing world. Imported cases of malaria have been increasing in New York City and throughout the United States during the past decade. The New York City Department of Health has modified its malaria surveillance program in order to improve the assessment of diagnosis and treatment of malaria in New York City residents and to provide appropriate advice to health professionals who treat these patients. OBJECTIVES: To describe the epidemiologic and clinical characteristics of laboratory-confirmed cases of malaria diagnosed in New York City residents from January 1, 1991, through December 31, 1996. METHODS: The retrospective study of case reports was carried out by the Malaria Surveillance Program of the Bureau of Communicable Diseases, New York City Department of Health, New York City, NY. It included the laboratory diagnosis of malaria and the species involved, and included also descriptive epidemiologic information of patients with malaria (age, sex, race/ethnicity, date and place of onset of illness, travel history, immigration status, previous history of malaria, history of blood transfusion, drugs used for treatment or prophylaxis), as well as a record of clinical complications of the infection (thrombocytopenia, hemolysis, anemia, cerebral malaria, renal failure, respiratory distress syndrome, fatal outcome). RESULTS: Malaria was diagnosed in 988 residents of New York City during the 5-year period from January 1, 1991, through December 31, 1995. The largest number of cases, 254 (26%), occurred in 1996, with the majority of these cases (76%) observed between the months of May and October. Sixty-four percent (627) of these cases were males. The age range of cases was from newborn (first day of life) to 83 years (median, 31 years). Of the 962 cases of whom the racial/ethnic identity was known, 580 (59%) were black/non-Hispanic and 255 (26%) were Asian/Pacific Islander. Travel outside of the United States was reported by 958 patients, the majority to Africa (569/958, 59%). Only 139 patients (14%) claimed the use of malaria prophylaxis during travel. Plasmodium falciparum was identified in 505 (51%) and P. vivax in 356 (36%) of the cases. Clinical complications included hemolysis with severe anemia, thrombocytopenia, cerebral malaria, renal failure, and respiratory distress syndrome. All four fatal cases involved infections with P. falciparum, either alone or in combination with another plasmodia species. CONCLUSIONS: Imported cases of malaria occur frequently in New York City and may be associated with serious complications. Health care providers should consider this diagnosis in patients who have recently travelled or arrived from abroad, presenting with headache, fever, and other constitutional symptoms. There are many missed opportunities for the use of malaria prophylaxis, and physicians should familiarize themselves with current recommendations for malaria prophylaxis for travel to areas of the world where people are at risk for the transmission of malaria.