Rationale:

• Prophylactic regimens change frequently because of regional variability in malaria risk (even within countries), resurgence of malaria in areas previously free of the disease, and the ongoing spread of drug-resistant parasites.
• Efficacy of malaria prophylaxis depends on the response of local parasite strains to antimalarial drugs and patient compliance.

Evidence:

• The risk of acquiring malaria varies according to: geographic region visited, travel destination within geographic areas (e.g., urban vs. rural), type of accommodations (e.g., camping vs. air-conditioned hotel), duration of stay (e.g., <1-week business trip vs. 3-month adventure travel), time of travel (high- vs. low-transmission season), altitude (<2,000 vs. >2,000 meters), and efficacy of and adherence to malaria prophylaxis (1). Another risk factor is poor knowledge and understanding of the extent and potential severity of malaria.
• Chloroquine-resistant P. falciparum is widespread in sub-Saharan Africa, Asia, and South America (2). Chloroquine resistance has also been reported in some areas of the Middle East: Iran, Yemen, Oman, and Saudi Arabia (3).
• Chloroquine-resistant P. falciparum malaria has not been reported from Mexico, Central America north of the Panama Canal, Haiti, and the Dominican Republic.
• Mefloquine-resistant P. falciparum now occurs in Thailand, Cambodia, Myanmar, and Vietnam (4) with scattered cases reported in the Amazon Basin (5).
• High-grade resistance of P. vivax to chloroquine has been reported in Oceania and parts of Southeast Asia (6; 7). Case reports of patients with chloroquine-resistant P. vivax have also been reported from Brazil (8), Guyana (9), Colombia (10), India (11), and Myanmar (12).
• Chloroquine-resistant P. malariae has been reported in Sumatra, Indonesia (13).

Comments:

• Up-to-date maps and information identifying malarious areas within countries can be found in the Traveler's Health section of the CDC Web site.
• When in doubt, contact the CDC Malaria Hotline (770-488-7788) for the geographical distribution of drug-resistant malaria and appropriate prophylactic regimens.
• Immigrants returning home to visit relatives are at high risk for acquiring malaria, because they often do not take malaria prophylaxis (they are going home and do not consider malaria a serious disease); they are often medically underserved and therefore less likely to seek pretravel advice; they often travel with children or when pregnant (e.g., returning to show family a new child or because they are pregnant); and they do not know that they have lost immunity to malaria and are at risk (14).