Mosquito-Borne Disease Risk Regions

Regional Risk Hierarchy

• The World Health Organization recommends that all travelers to sub-Saharan Africa face high risk in both rural and many urban areas, with chloroquine-resistant falciparum malaria being common throughout the region 1, 2, 3
• The Centers for Disease Control and Prevention notes that during 1980-1988, 80% (1,222 of 1,534 cases) of P. falciparum infections among U.S. civilians were acquired in sub-Saharan Africa, despite only an estimated 90,000 Americans traveling there annually 4
• The World Health Organization reports that of 37 fatal malaria infections, 27 were acquired in sub-Saharan Africa 4
• Travelers to Africa spend considerable time, including evening and nighttime hours, in rural areas where malaria risk is highest, according to the Centers for Disease Control and Prevention 4
• The Indian subcontinent poses risk in all areas except high mountains, with both rural areas and some cities affected, as stated by the World Health Organization 1, 2, 3, 5
• P. vivax predominates, but falciparum malaria is present and often resistant to chloroquine in South and Southeast Asia, according to the World Health Organization 1, 2, 3, 5
• Rural agricultural areas associated with rice production and flooding irrigation in Asia carry the highest risk for Japanese encephalitis, as reported by the Centers for Disease Control and Prevention 7
• A high risk of highly chloroquine-resistant malaria exists in the Amazon basin, particularly in Brazil's "legal Amazon" and adjacent countries to the north and west, according to the World Health Organization 1, 2, 3
• Approximately 500 human cases are reported annually in South America, primarily among men with occupational exposures in forested areas, though the disease is substantially underreported, as noted by the Centers for Disease Control and Prevention 8

Critical Risk Factors Across All Regions

• Malaria transmission occurs mainly between dusk and dawn due to nocturnal feeding habits of Anopheles mosquitoes, as stated by the World Health Organization 9
• In temperate areas of Asia, transmission is seasonal with human disease peaking in summer and fall, according to the Centers for Disease Control and Prevention 7
• Rural agricultural areas, particularly those with rice production and flooding irrigation, carry the highest risk, as reported by the Centers for Disease Control and Prevention 7
• Urban areas generally pose lower risk, though some cities in Asia remain affected, according to the World Health Organization 1, 2, 3, 5
• Short-term travelers (<1 month) restricted to major urban areas face minimal risk for Japanese encephalitis, as noted by the Centers for Disease Control and Prevention 7
• The Centers for Disease Control and Prevention advises against underestimating risk based on short travel duration alone, as brief trips with extensive outdoor or nighttime exposure in rural areas during active transmission periods can still result in infection 7