Diseases potentially acquired by travel to East Africa

INTRODUCTION — East Africa is comprised of Burundi, Comoros, Djibouti, Eritrea, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Mozambique, Réunion, Rwanda, Seychelles, Somalia, Tanzania, and Uganda. This region encompasses tropical rain forests in the west and center, desert areas in the north, and wooded steppes in the east.

ARTHROPOD-BORNE DISEASES

Malaria — Malaria is a major risk for most travelers to East Africa. Endemic areas exist in all countries in this region except for the islands of Réunion and Seychelles and at altitudes over 2600 meters. Except for Mauritius, Plasmodium falciparum is the predominant cause of malaria, and chloroquine resistance is widespread. Within endemic areas, transmission occurs year round [1]:

●Burundi – Risk throughout the year in the whole country

●Comoros – Risk throughout the year in the whole country

●Djibouti – Risk throughout the year in the whole country

●Eritrea – Risk throughout the year in the whole country below 2200 meters. There is no risk in Asmara.

●Ethiopia – Risk throughout the year in the whole country below 2500 meters, except in the city of Addis Ababa.

●Kenya – Risk throughout the year in the whole country in areas below 2500 meters.

●Madagascar – Risk throughout the year in the whole country

●Malawi – Risk throughout the year in the whole country

●Mauritius – No risk

●Mozambique – Risk throughout the year in the whole country

●Réunion – No risk

●Rwanda – Risk throughout the year in the whole country

●Seychelles – No risk

●Somalia – Risk throughout the year in the whole country

●Tanzania – Risk throughout the year in the whole country below 1800 meters

●Uganda – Risk throughout the year in the whole country

Issues related to prevention of malaria in travelers are discussed separately. (See "Prevention of malaria infection in travelers".)

Yellow fever — Yellow fever is endemic throughout most of East Africa [2]. 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 East Africa. In addition, many neighboring countries of endemic regions require yellow fever certificates for travelers coming from infected areas. (See "Immunizations for travel", section on 'Yellow fever vaccine' and "Yellow fever: Treatment and prevention", section on 'Prevention'.)

Dengue — Epidemics of dengue fever have occurred in East Africa. (See "Dengue virus infection: Prevention and treatment".)

African trypanosomiasis — African trypanosomiasis (sleeping sickness) is endemic throughout much of East Africa. Countries with the highest endemicity include Mozambique, Tanzania, and Uganda. (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 [3].

Leishmaniasis — Both cutaneous and visceral leishmaniasis occur in relatively restricted areas of East Africa, especially Sudan, Kenya, Ethiopia, and Somalia. Sandflies of the genus Phlebotomus are the vectors. Visceral leishmaniasis occurs both sporadically and in epidemics. The main reservoirs are rodents and small carnivores. Leishmania aethiopica is the principal cause of cutaneous leishmaniasis in the Ethiopian highlands and Kenya. The hyrax is the main reservoir. (See "Visceral leishmaniasis: Epidemiology and control" and "Cutaneous leishmaniasis: Epidemiology and control".)

Onchocerciasis — Onchocerciasis (river blindness) is caused by the roundworm Onchocerca volvulus and is transmitted to humans by Simulium blackflies. Endemic areas are widespread through parts of East Africa, determined by the distribution of the vector. Blackflies 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 [4,5]. (See "Onchocerciasis".)

Rickettsioses — Several rickettsioses are endemic in East Africa. Environments suitable for transmission of both epidemic typhus (caused by Rickettsia prowazekii) and murine typhus (caused by Rickettsia typhi) are present in the region.

●Epidemic typhus is transmitted by the body louse, and human conditions that favor the proliferation of lice occur during cold weather (eg, rural East African highlands) and during war or natural disasters (eg, among refugees). (See "Epidemic typhus".)

●Murine typhus is transmitted to humans by rat or cat fleas and occurs most commonly in urban settings. (See "Murine typhus".)

In addition, tick typhus, caused by Rickettsia conorii, Rickettsia africae, and others, occurs sporadically, particularly in East and Southern Africa [6]. Its epidemiology is closely associated with ticks.

Chikungunya fever — Chikungunya fever has been increasingly reported in the region [7,8]. 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 was initially observed in Zika Forest, Uganda; it has also been observed elsewhere in East Africa [9-12]. 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 — East Africa is regarded as a high-risk area for the development of travelers' diarrhea, with enterotoxigenic Escherichia coli being the most common pathogen identified [13]. (See "Travelers' diarrhea: Epidemiology, microbiology, clinical manifestations, and diagnosis".)

Cholera — Cholera outbreaks are frequent occurrences in East Africa. (See "Cholera: Epidemiology, clinical features, and diagnosis" and "Cholera: Treatment and prevention", section on 'Introduction'.)

Typhoid — Typhoid fever is endemic throughout most of East Africa, although the risk is generally less than in South Asia. (See "Enteric (typhoid and paratyphoid) fever: Epidemiology, clinical manifestations, and diagnosis".)

Hepatitis A and E — Hepatitis A virus is endemic throughout East Africa. Hepatitis E has been responsible for both outbreaks and sporadic cases of hepatitis 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'.)

Schistosomiasis — Schistosomiasis due to Schistosoma haematobium and Schistosoma mansoni is widespread in East Africa and is recognized as a major hazard for travelers [14,15]. Transmission occurs through exposure to fresh water (lakes and slow-moving rivers) in endemic regions. Lake Malawi is a major source of infection in travelers [16]. (See "Schistosomiasis: Epidemiology and clinical manifestations".)

Dracunculiasis — Within East Africa, guinea worm (Dracunculus medinensis) infection is endemic in Ethiopia. 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 is relatively common in areas of Africa. (See "Epidemiology and control of echinococcosis".)

OTHER INFECTIONS

Meningococcal disease — Sub-Saharan 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, which 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 — Sub-Saharan 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 [17]. (See "Global epidemiology of HIV infection".)

Other sexually transmitted diseases — Sexually transmitted disease is a major public health problem in parts of East Africa. Contact with sex workers involves a high risk.

Hepatitis B and C — Hepatitis B virus is highly endemic throughout East 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".)

Plague — The majority of the world's reported cases of plague come from East Africa. Since August 2017, over 2400 cases of confirmed, probable, or suspected plague have been reported from Madagascar [18,19]. The majority of these cases have been reported to be pneumonic plague. (See "Epidemiology, microbiology and pathogenesis of plague (Yersinia pestis infection)" and "Clinical manifestations, diagnosis, and treatment of plague (Yersinia pestis infection)".)

Rabies — Rabies is endemic throughout East 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 East Africa. (See "Rabies immune globulin and vaccine" and "Indications for post-exposure rabies prophylaxis" and "Immunizations for travel", section on 'Rabies vaccine'.)

Tuberculosis — Tuberculosis is relatively common in many parts of East 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, several other viral hemorrhagic fevers have caused localized outbreaks in East Africa. These include Ebola hemorrhagic fever, Rift Valley fever (RVF), and Crimean-Congo hemorrhagic fever (CCHF).

Ebola virus — 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".)

Rift Valley fever — RVF is an acute, febrile illness caused by the Rift Valley fever virus, which belongs to the family of Bunyaviridae, genus Phlebovirus [21]. Transmission to humans occurs via bites from infected mosquitoes or, more frequently, through close contact with infected mammals.

RVF is found in many savanna regions of East Africa, especially following heavy rainfall [22]. Outbreaks of Rift Valley fever have also been documented in West Africa [23,24]. Outbreaks have occurred in Kenya and Somalia; the largest one occurred in Kenya during the 1997 to 1998 season when approximately 89,000 people were infected and 473 died [25]. In the Kenyan outbreak, more than 404 cases were reported with 118 deaths from November 2006 to January 25, 2007, a case-fatality rate of 29 percent [21].

The most frequently reported symptoms include fever, headache, bleeding, malaise, muscle pain, back pain, vomiting, and joint pain.

The diagnosis of RVF is established by the detection of viral RNA by polymerase chain reaction or detection of IgM antibodies against RVF virus by enzyme-linked immunosorbent assay [21].

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 East Africa. The most important species include the saw-scaled or carpet viper (Echis spp), puff adder (Bitis arietans), and spitting cobra (Naja nigricollis, N. mossambica, and others). (See "Snakebites worldwide: Management" and "Snakebites worldwide: Clinical manifestations and diagnosis".)

High-altitude disease — There are many high-altitude areas in East Africa, several of which are popular tourist destinations. Kilimanjaro (5895 meters) is the highest peak in the African continent and is climbed by many travelers each year, including many with limited trekking or climbing experience. Traditional ascent itineraries are rapid, and acute mountain sickness is common. (See "High-altitude illness: Physiology, risk factors, and general prevention".)

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".)

SUMMARY

●East Africa is comprised of Burundi, Comoros, Djibouti, Eritrea, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Mozambique, Réunion, Rwanda, Seychelles, Somalia, Tanzania, and Uganda. This region encompasses tropical rain forests in the west and center, desert areas in the north, and wooded steppes in the east. (See 'Introduction' above.)

●Malaria is a major risk for most travelers to East Africa. Endemic areas exist in all countries in this region except for the islands of Réunion and Seychelles and at altitudes over 2600 meters. Except for Mauritius, 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, Rift Valley fever, and Crimean-Congo hemorrhagic fever. (See 'Arthropod-borne diseases' above.)

●Foodborne and waterborne diseases include travelers’ diarrhea, cholera, typhoid, hepatitis A, hepatitis E, schistosomiasis, 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, plague, rabies, and tuberculosis. (See 'Other infections' above.)