INTRODUCTION — West Africa comprises Benin, Burkina Faso, Cape Verde, Côte d'Ivoire, the Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, São Tomé and Príncipe, Senegal, Sierra Leone, and Togo. This region encompasses tropical rain forests in the west and south and desert areas in the north.
ARTHROPOD-BORNE DISEASES
Malaria — Malaria is a major risk for most travelers to West Africa [1]. Endemic areas exist in all countries in this region. Except for Cape Verde, Plasmodium falciparum is the predominant cause of malaria, and chloroquine resistance is widespread. Country-specific risk areas are listed below [2]:
●Benin – Risk throughout the year in the whole country
●Burkina Faso – Risk throughout the year in the whole country
●Cape Verde – Limited risk from August through November on Santiago Island and Boa Island
●Côte d’Ivoire – Risk throughout the year in the whole country
●The Gambia – Risk throughout the year in the whole country
●Ghana – Risk throughout the year in the whole country
●Guinea – Risk throughout the year in the whole country
●Guinea-Bissau – Risk throughout the year in the whole country
●Liberia – Risk throughout the year in the whole country
●Mali – Risk throughout the year in the whole country
●Mauritania – Risk throughout the year in the whole country, except in the northern areas: Dakhet-Nouadhibou and Tiris-Zemour.
●Niger – Risk throughout the year in the whole country
●Nigeria – Risk throughout the year in the whole country
●São Tomé and Príncipe – Risk throughout the year in the whole country
●Senegal – Risk throughout the year in the whole country
●Sierra Leone – Risk throughout the year in the whole country
●Togo – Risk throughout the year in the whole country
Issues related to malaria prophylaxis are discussed separately. (See "Prevention of malaria infection in travelers".)
Yellow fever — Yellow fever is endemic throughout most of West Africa [3]. Several species of mosquitoes are the reservoir of yellow fever virus and transmit infection to monkeys as well as humans. In Africa, the main mosquito vectors are Aedes aegypti and Aedes simpsoni. (See "Yellow fever: Epidemiology, clinical manifestations, and diagnosis".)
Three types of transmission cycle for yellow fever exist:
●Sylvatic (or jungle) yellow fever occurs among monkeys in tropical rain forests; sporadic cases occur in humans who enter the forest.
●Intermediate yellow fever occurs in semi-humid savannas where semi-domestic mosquitoes infect both humans and monkeys and cause small-scale epidemics.
●Urban yellow fever occurs when migrants introduce the virus into areas of high human population density, resulting in large epidemics.
Yellow fever vaccine is required for entry into most countries in West Africa. In addition, many neighboring countries of endemic regions require yellow fever certificates for travelers coming from infected areas. Yellow fever vaccine is generally safe and very effective but, as a live virus vaccine, may be contraindicated in patients with immunocompromise. (See "Immunizations for travel", section on 'Yellow fever vaccine'.)
Dengue — Many areas in West Africa are suitable for dengue virus transmission. (See "Dengue virus infection: Prevention and treatment".)
African trypanosomiasis — African trypanosomiasis (sleeping sickness) is endemic throughout much of West Africa. The countries in West Africa for which trypanosomiasis remains an important public health problem are Côte d'Ivoire and Guinea. (See "Human African trypanosomiasis: Treatment and prevention".)
Two different species of parasite cause two epidemiologically distinct diseases, both of which are transmitted by tsetse flies:
●West African trypanosomiasis is caused by Trypanosoma brucei gambiense. Humans are the primary reservoir, it occurs mainly in wooded areas along rivers, and tourists are rarely infected.
●East African trypanosomiasis is caused by Trypanosoma brucei rhodesiense. Antelope and cattle are the primary reservoirs, it occurs mainly in savanna and woodland areas, and it has been reported in tourists visiting game parks [4].
Onchocerciasis — Onchocerciasis (river blindness) is caused by the roundworm Onchocerca volvulus and is transmitted to humans by Simulium black flies. Endemic areas are widespread throughout West Africa, determined by the distribution of the vector. Black flies breed in fast-flowing streams in both savanna and rainforest. The risk to short-term travelers of developing onchocerciasis is small, although acquisition after only four to six weeks' exposure has been documented [5,6]. (See "Onchocerciasis".)
Leishmaniasis — Both cutaneous and visceral leishmaniasis occur in relatively restricted areas of West Africa, although cutaneous leishmaniasis is more predominant. Sand flies of the genus Phlebotomus are the vectors. (See "Visceral leishmaniasis: Epidemiology and control" and "Cutaneous leishmaniasis: Epidemiology and control".)
Rickettsioses — Several rickettsioses are endemic in West Africa [7]. Environments suitable for transmission of both epidemic typhus (caused by Rickettsia prowazekii) and murine typhus (caused by Rickettsia typhi) are present in West Africa. Epidemic typhus is transmitted by the body louse. Conditions that favor the proliferation of lice include crowding in the setting cold weather, war, and natural disasters. Murine typhus is transmitted to humans by rat or cat fleas and occurs most commonly in urban settings. (See "Murine typhus" and "Epidemic typhus".)
In addition, tick typhus, caused by Rickettsia conorii, Rickettsia africae, and others, occurs sporadically, and its epidemiology is closely associated with ticks [8].
Chikungunya fever — Chikungunya fever has been increasingly reported in the region [9]. Infection is transmitted by the bite of an Aedes mosquito, and the illness is characterized by sudden onset of fever and severe arthralgias. (See "Chikungunya fever: Epidemiology, clinical manifestations, and diagnosis".)
Zika virus — Zika virus has been observed in West Africa [10-14]. Symptoms of Zika virus infection include fever, rash, joint pain, and conjunctivitis. The illness is usually mild with symptoms lasting several days to a week; severe disease requiring hospitalization is uncommon. Asymptomatic infection is common, and only about one in five individuals who become infected with Zika virus become ill.
Zika virus is discussed further separately. (See "Zika virus infection: An overview".)
FOODBORNE AND WATERBORNE DISEASES
Travelers' diarrhea — West Africa is a high-risk area for the development of travelers' diarrhea. Enterotoxigenic Escherichia coli is the most common pathogen identified [15]. (See "Travelers' diarrhea: Epidemiology, microbiology, clinical manifestations, and diagnosis".)
Cholera — Cholera outbreaks are frequent occurrences in West Africa. (See "Cholera: Clinical features, diagnosis, treatment, and prevention".)
Typhoid — Typhoid fever is endemic throughout most of West Africa, although the risk is generally less than in South Asia. (See "Enteric (typhoid and paratyphoid) fever: Epidemiology, clinical manifestations, and diagnosis" and "Immunizations for travel", section on 'Typhoid vaccine'.)
Hepatitis A and E — Hepatitis A virus is endemic throughout West Africa. Hepatitis E has been responsible for both outbreaks and sporadic cases of hepatitis [16] and is probably widespread in the region. (See "Hepatitis A virus infection in adults: Epidemiology, clinical manifestations, and diagnosis" and "Hepatitis E virus infection" and "Immunizations for travel", section on 'Hepatitis A vaccine'.)
Poliomyelitis — Nigeria is the only African country where endemic wild-type polio virus occurs; cases there account for about 65 percent of global cases of poliomyelitis [17]. (See "Global poliomyelitis eradication" and "Immunizations for travel", section on 'Poliovirus vaccine'.)
Schistosomiasis — Schistosomiasis due to Schistosoma haematobium and Schistosoma mansoni is widespread in parts of West Africa and is recognized as a major hazard for travelers [18]. Transmission occurs through exposure to fresh water (lakes and slow-moving rivers) in endemic regions, and many travelers are only diagnosed with the disease on post-travel screening. (See "Schistosomiasis: Epidemiology and clinical manifestations".)
Paragonimiasis — Endemic foci of the lung fluke Paragonimus westermani are present in West Africa. (See "Paragonimiasis".)
Dracunculiasis — Guinea worm (Dracunculus medinensis) infection rates have fallen dramatically, although small numbers have been reported from West Africa. The disease is prevalent in areas where people bathe and wade in water used also for drinking. (See "Miscellaneous nematodes", section on 'Dracunculiasis'.)
Echinococcosis — Hydatid disease continues to be relatively common in areas of Africa. (See "Epidemiology and control of echinococcosis".)
OTHER INFECTIONS
Meningococcal disease — West Africa has a unique pattern of epidemic meningococcal disease. Epidemics occur during the dry season in the "meningitis belt"; the most affected countries are Chad, Nigeria, Burkina Faso, Mali, and Niger. Major epidemics occur every 5 to 10 years in this area, affecting hundreds of thousands of people. Most epidemics are caused by serogroup A and, less often, serogroup C. Both of these serogroups are covered by the polysaccharide meningococcal vaccine that is recommended for travelers to countries affected by meningococcal outbreaks. (See "Treatment and prevention of meningococcal infection" and "Immunizations for travel", section on 'Meningococcal vaccine'.)
HIV infection — West Africa is the region of the world most affected by the HIV/AIDS pandemic. The main mode of transmission in the region is heterosexual contact. Unprotected sex with locals carries the greatest risk of transmission to travelers [19]. (See "Global epidemiology of HIV infection".)
Other sexually transmitted diseases — Sexually transmitted disease is a major public health problem in parts of West Africa. Contact with sex workers involves a high risk.
Hepatitis B and C — Hepatitis B virus is highly endemic throughout West Africa. (See "Hepatitis B virus: Clinical manifestations and natural history".)
The prevalence of hepatitis C is also high in many regions. (See "Clinical manifestations and natural history of chronic hepatitis C virus infection" and "Clinical manifestations, diagnosis, and treatment of acute hepatitis C virus infection in adults".)
Rabies — Rabies is endemic throughout West Africa and has been reported with increasing frequency [20]. The domestic dog plays a key role in maintenance and transmission of rabies, although other animals (eg, mongoose and fox) are important in some regions. Postexposure treatment is recommended following all potential exposures, and prophylaxis should be considered by travelers spending significant periods of time in West Africa. (See "Rabies immune globulin and vaccine" and "Indications for post-exposure and pre-exposure rabies prophylaxis" and "Immunizations for travel", section on 'Rabies vaccine'.)
Tuberculosis — Tuberculosis is relatively common in many parts of West Africa, although short-term travelers from countries of low endemicity are generally not considered at increased risk of infection.
Viral hemorrhagic fever — In addition to yellow fever and dengue, other viral hemorrhagic fevers have caused outbreaks in the region. These include Ebola virus, Lassa fever and Crimean-Congo hemorrhagic fever (CCHF). Most of these infections are zoonoses and are transmitted to humans by bites of infected ticks or mosquitoes or via aerosols from infected rodents.
Ebola virus — The 2014 to 2016 outbreak in West Africa was the largest and most complex Ebola outbreak since the Ebola virus was first discovered in 1976. It started in Guinea then spread across land borders to Sierra Leone and Liberia, by air (one traveler only) to Nigeria, and by land (one traveler) to Senegal. The most severely affected countries were Guinea, Sierra Leone, and Liberia. Other issues related to Ebola virus are discussed separately. (See "Epidemiology and pathogenesis of Ebola virus disease" and "Clinical manifestations and diagnosis of Ebola virus disease".)
Lassa fever — Transmission of Lassa fever occurs through aerosol spread, either from rodents (multimammate rat) or through close contact with infected individuals. The incubation period is about 10 days (range 6 to 21 days). (See "Lassa fever".)
Person-to-person transmission can occur via exposure via percutaneous injury to body fluids that are infectious (eg, blood, urine, vomitus), unprotected contact with potentially infectious material (eg, touching vomitus), and mucosal exposure from splashes of body fluids.
Rift Valley fever — Rift Valley fever (RVF) is an acute, febrile illness caused by the Rift Valley fever virus. RVF is found in many savanna regions of East Africa; outbreaks of have also been documented in West Africa [21-23]. (See "Diseases potentially acquired by travel to East Africa", section on 'Rift Valley fever'.)
Transmission to humans occurs via bites from infected mosquitoes or, more frequently, through close contact with infected mammals. The most frequently reported symptoms include fever, headache, bleeding, malaise, muscle pain, back pain, vomiting, and joint pain.
Crimean-Congo hemorrhagic fever — Crimean-Congo hemorrhagic fever is a severe, potentially fatal disease in humans caused by CCHF virus. Issues related to CCHF are discussed separately. (See "Diseases potentially acquired by travel to Central Africa", section on 'Crimean-Congo hemorrhagic fever'.)
OTHER HAZARDS
Snake bites — Venomous snakes are present throughout West Africa. The most important species include the saw-scaled or carpet viper (Echis spp), puff adder (Bitis arietans), and spitting cobra (Naja nigricollis, Naja mossambica, and others). (See "Snakebites worldwide: Management".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Travel medicine".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Ebola (The Basics)")
SUMMARY
●West Africa is comprised of Benin, Burkina Faso, Cape Verde, Côte d'Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Sao Tome and Principe, Senegal, Sierra Leone, and Togo. This region encompasses tropical rain forests in the west and south and desert areas in the north. (See 'Introduction' above.)
●Malaria is a major risk for most travelers to West Africa. Endemic areas exist in all countries in this region. Except for Cape Verde, Plasmodium falciparum is the predominant cause of malaria, and chloroquine resistance is widespread. (See 'Malaria' above.)
●Other arthropod-borne diseases include yellow fever, dengue, African trypanosomiasis, onchocerciasis, and rickettsioses. Other viral hemorrhagic fevers include Ebola virus, Lassa fever, and Crimean-Congo hemorrhagic fever. (See 'Arthropod-borne diseases' above.)
●Foodborne and waterborne diseases include travelers’ diarrhea, cholera, typhoid, hepatitis A, hepatitis E, poliomyelitis, schistosomiasis, paragonimiasis, dracunculiasis, and echinococcosis. (See 'Foodborne and waterborne diseases' above.)
●Other infections include meningococcal disease, HIV infection and other sexually transmitted diseases, hepatitis B, hepatitis C, rabies, and tuberculosis. (See 'Other infections' above.)
