Vector-borne infections are common and widespread and pose a major risk to local residents and travelers. Access to clean water and sanitary disposal of waste are limited in many areas, so infections related to fecal contamination of food and water remain common and widespread. Vaccine-preventable diseases such as measles, mumps, rubella, poliomyelitis, and diphtheria persist in the region.
The most common cause of systemic febrile illness in travelers to this region is malaria caused by Plasmodium falciparum. Subacute or chronic infections in immigrants (and long-term residents) from the area include tuberculosis, hepatitis B, HIV, lymphatic filariasis, onchocerciasis, loiasis, schistosomiasis, echinococcosis, leprosy, and intestinal parasites.
Vector-borne infections: Malaria transmission is intense in many parts of the region, including urban areas, where falciparum malaria, much of it resistant to chloroquine, predominates. Sporadic cases and outbreaks of yellow fever have occurred in at least 18 of the countries (especially in West Africa) since 2000; outbreaks were reported in 2005 from Guinea, the Sudan, Côte d’Ivoire, Mali, Senegal, Burkina Faso, and Sierra Leone. All countries in the region are considered to be in the endemic zone, and unvaccinated travelers are at risk for infection. Official reports of yellow fever reflect only a small percentage of all infections. African trypanosomiasis has increased in Africa (it is epidemic in Angola, Democratic Republic of Congo, and the Sudan; and highly endemic in Cameroon, Central African Republic, Chad, Congo, Côte d’Ivoire, Guinea, Mozambique, Uganda, and Tanzania; low levels are found in most of the other countries), and an increase in travelers has been noted since 2000. Most had exposures in Tanzania and Kenya, reflecting common tourist routes. Trypanosoma brucei gambiense is found in focal areas of west-ern and central Africa; T. b. rhodesiense, which causes more acute illness, is found in east Africa. Vector-borne viral infections include dengue fever, Crimean-Congo hemorrhagic fever,* Rift Valley fever,* West Nile fever, chikungunya fever, and O’nyong nyong fever. Lymphatic filariasis is present in many areas; onchocerciasis is widely distributed around river systems, especially in West and Central Africa and as far east as Ethiopia. Another filarial infection, loiasis, is widely distributed in the tropical rain forest, especially in Central and West Africa. Filarial infections are rare in short-term travelers. The rickettsial infections murine typhus, louse-borne typhus, and African tick bite fever (due to Rickettsia africae) occur in the region. African tick-bite fever has been increasingly recognized in travelers to rural areas. Murine typhus is more common in coastal areas. Tungiasis (penetration of the skin by sand fleas) is widespread in tropical Africa, especially West Africa, including Madagascar.
In 2005-2006, massive outbreaks of chikungunya occurred on island countries in the southwest Indian Ocean (Réunion, Mayotte, Mauritius, and Seychelles). Infections were also imported by returning travelers to Europe (160 imported cases in France alone) and the United States.
Tick-borne relapsing fever is widespread in eastern and central Africa and sporadic elsewhere. Epidemics of louse-borne relapsing fever have occurred in the past but pose little risk to usual travelers. Visceral leishmaniasis is endemic in Ethiopia, Kenya, and Sudan (and has caused large epidemics); it is found in the savanna parts of the region. Cutaneous leishmaniasis is also found in the savanna and in Sudan, Ethiopia, and Kenya. Myiasis transmitted by the tumbu fly can affect travelers.
Food- and water-borne infections: Dysentery and diarrhea are common in local populations; diarrhea in travelers may be caused by bacteria, viruses, and parasites (especially Giardia, Cryptosporidium and Entamoeba histolytica). Cholera is sporadic and epidemic. A wave of outbreaks began in West Africa in 2005. Large outbreaks have been re-ported from southern Sudan and Angola in 2006. Risk of hepatitis A is wide-spread; sporadic cases and outbreaks of hepatitis E occur. Polio persists in Nigeria (799 confirmed cases in 2005) and was endemic in Niger in 2005; sporadic cases also occurred in Angola, Cameroon, Chad, Eritrea, Ethiopia, Mali, and Somalia in 2005-2006. Other risks to travelers include typhoid (a large outbreak occurred in the Democratic Republic of the Congo in 2004-2005) and paratyphoid fever, amebiasis, and brucellosis. Dracunculiasis cases were re-ported from nine African countries in 2005, with the highest number of cases in Sudan, Ghana, and Mali, but it is rare in travelers. Intestinal parasites are common in residents in many parts of region but are rare in short-term travelers.
Airborne and person-to-person transmission: The estimated annual incidence rates of tuberculosis (per 100,000) are >100 in all countries and >300 in much of region. Frequent epidemics of serogroup A meningococcal disease occur during the dry sea-son (December through June) in a band of countries from Senegal to Ethiopia. Severe outbreaks have occurred in Burkina Faso, Chad, Mali, Niger, Nigeria, Ethiopia, and the Sudan. Serogroup W135 emerged in Burkina Faso in 2002, causing a large epidemic (13,000 cases). It was the predominant pathogen in 2006 in Kenya, Sudan (W. Darfur camps), and Uganda (Gulu district). Nosocomial and in-trafamilial spread of Ebola* occurs in outbreaks (Sudan, Democratic Republic of the Congo, Côte d’Ivoire, and Gabon). Nosocomial spread of Marburg fever virus (an outbreak occurred in Angola in 2005) and Lassa fever virus* has also occurred.
Sexually transmitted and blood-borne infections: The estimated prevalence of HIV in adults (15-49 years) ranges from 1% to 15% in most countries. In most of the region, prevalence of chronic infection with hepatitis B virus exceeds 8%. HTLV-1 is endemic in parts of Central and West Africa. Common causes of genital ulcer disease include chancroid, syphilis, and herpes simplex.
Zoonotic infections: Dogs are the most important source of rabies, which is found throughout the region. A wild rodent is the reservoir host for Lassa fever virus,* which is endemic in West Africa; cases have also been documented in the Central African Republic. Echinococcosis* is widespread in animal breeding areas. Sporadic cases and outbreaks of anthrax* occur in the region (it is hyperendemic in Zambia, Ethiopia, Niger, and Chad and in several countries along the western coast). Monkeypox* is found in West and Central Africa, primarily in remote villages in rain forest areas. Plague* is enzootic, and sporadic cases and outbreaks occur in humans. (Outbreaks have occurred since 2000 in Madagascar, Malawi, Mozambique, Uganda, and Tanzania.) Ituri District (Oriental Province) in the Democratic Republic of Congo reports about 1,000 cases per year and was the site of an outbreak in 2006. Q fever* (airborne spread) is found, especially in West Africa, where livestock breeding is common. Avian influenza (H5N1) was found in poultry in 2006 in Nigeria, Niger, Cameroon, Burkina Faso, Sudan, and Côte d’Ivoire. One human case occurred in Djibouti in 2006.
Soil and water-associated infections: Schistosomiasis due to Schistosoma mansoni and S. haematobium is widespread; S. intercalatum has a more limited distribution (West Africa). Mycobacterium ulcerans (the cause of Buruli ulcer) is most concentrated in West Africa and is increasing in prevalence. Rare cases have occurred in travelers. Leptospirosis* (both sporadic cases and outbreaks) occurs in tropical areas. Other risks include mycetoma and histoplasmosis.
Other hazards: Motor vehicle accidents and other injuries, including violent injury with assault rifles and other weapons, and sexual assaults occur. Snake bites and aflatoxin contamination of grains are common, especially in rural areas. Screening of blood before transfusion is inadequate in many hospitals.
