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Diseases potentially acquired by travel to Central Africa

Diseases potentially acquired by travel to Central Africa
Literature review current through: Jan 2024.
This topic last updated: Nov 01, 2022.

INTRODUCTION — Central Africa is comprised of Angola, Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea, Gabon, South Sudan, Sudan, Democratic Republic of Congo (Zaire), and Zambia. This region encompasses tropical rain forests, desert areas, and wooded areas.

ARTHROPOD-BORNE DISEASES

Malaria — Malaria is a major risk for travelers to Central Africa. Endemic areas exist in all countries in this region. Plasmodium falciparum is the predominant cause of malaria, and chloroquine resistance is widespread. Within endemic areas, transmission occurs year round [1]:

Angola – Risk throughout the year in the whole country

Cameroon – Risk throughout the year in the whole country

Central African Republic – Risk throughout the year in the whole country

Chad – Risk throughout the year in the whole country

Congo – Risk throughout the year in the whole country

Equatorial Guinea – Risk throughout the year in the whole country

Gabon – Risk throughout the year in the whole country

South Sudan – Risk throughout the year in the whole country

Sudan – Risk throughout the year in the whole country.

Democratic Republic of Congo (Zaire) – Risk throughout the year in the whole country

Zambia – 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 Central 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 (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 Central 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 — Many areas in Central Africa are suitable for dengue virus transmission. (See "Dengue virus infection: Prevention and treatment".)

Other viral hemorrhagic fevers — In addition to yellow fever and dengue, several other viral hemorrhagic fevers have caused localized outbreaks in Africa. Of particular relevance to Central Africa are Ebola, Marburg hemorrhagic fever, and Crimean-Congo hemorrhagic fever (CCHF).

Ebola virus — Ebola virus was first identified in Sudan and Democratic Republic of Congo (Zaire) in 1976 [3]. Transmission occurs through direct contact with body fluid from infected individuals. Mortality rates differ among Ebola viruses isolated from different regions; mortality rates of 70 to 90 percent were seen in association with Democratic Republic of Congo (Zaire) Ebola virus infections but were lower with Sudan Ebola virus [4]. Variations in outcome during an epidemic may result from genetically determined differences in innate immune responses to the virus.

Serologic studies suggest that mild or asymptomatic episodes occur, although they are uncommon. A population-based serosurvey of more than 900 residents in Gabon found a seroprevalence of 1.4 percent [5].

The natural reservoir for Ebola virus may be bats; in a field study where more than 1000 small vertebrates were collected during Ebola outbreaks in humans and great apes, asymptomatic infection was identified in three species of fruit bats [6]. Human infection may be countered by educational programs, since local populations eat fruit bats where Ebola outbreaks have occurred. The outbreak of Ebola in the Democratic Republic of Congo in 2014 was not linked to the large outbreak in West Africa. In April 2022, an Ebola outbreak in Equateur Province of the Democratic Republic of Congo was declared. This is the third outbreak in the province since 2018. (See "Epidemiology and pathogenesis of Ebola virus disease".)

Marburg virus — Marburg hemorrhagic fever is a highly fatal disease caused by an RNA virus in the Filoviridae family [7]. Marburg virus infection is rare and limited to countries in Central Africa [8]. The reservoir of infection is unknown.

Marburg hemorrhagic fever was first identified in 1967 after an infectious disease physician in a university hospital in Marburg, Germany, saw patients with a severe febrile illness associated with hemorrhage and shock [9]. All the patients worked for a pharmaceutical manufacturer where they had contact with African green monkeys. The virus that was isolated was unrelated to any other known family of viruses and had a unique branching morphology.

Marburg virus can be transmitted to humans through direct contact with body fluids (eg, blood, saliva, and urine) of an infected person or animal or through unsterile injections [9]. Marburg virus appears to be easily transmissible since healthcare workers have also been infected. The virus can survive for as long as several days on contaminated surfaces. The incubation period is estimated to be 5 to 10 days.

Marburg virus infection presents acutely with fever, chills, headache, and myalgia. After about five days, symptoms progress to include nausea, vomiting, chest pain, sore throat, abdominal pain, and diarrhea. A maculopapular rash may also occur. Over time, signs and symptoms become increasingly severe and can include jaundice, weight loss, and delirium. Patients die from septic shock with massive hemorrhage and multiorgan failure.

A serosurvey of 121 household contacts suggests that mild or asymptomatic disease is rare [10]. Diagnosis of suspected Marburg infection is established on clinical and epidemiologic grounds and confirmed by polymerase chain reaction (PCR), antigen-capture enzyme-linked immunosorbent assay (ELISA), immunoglobulin (Ig)M ELISA, or virus isolation [10].

Crimean-Congo hemorrhagic fever — Crimean-Congo hemorrhagic fever is a severe, potentially fatal disease in humans caused by CCHF virus [11]. The disease has been documented in parts of Africa, Asia, Eastern Europe, and the Middle East. In the Central African region, countries regarded as endemic for CCHF are Central African Republic, the Democratic Republic of Congo, South Sudan, and Sudan. Transmission to humans occurs through tick bites, contact with a patient with CCHF during the acute stage of infection, or contact with blood or tissue from infected livestock [12].

The typical course of CCHF has four distinct phases: incubation, prehemorrhagic, hemorrhagic, and convalescence [13]. The incubation period that follows a tick bite is usually short (three to seven days). The prehemorrhagic period is characterized by the sudden onset of fever, headache, myalgia, and dizziness [14]. Additional symptoms of diarrhea, nausea, and vomiting are also seen in some cases. After approximately three days, hemorrhagic manifestations from petechiae, large hematomas, and frank bleeding (vaginal, gastrointestinal, nose, urinary, and respiratory tracts) usually follow [15]. The convalescence period begins in survivors about 10 to 20 days after onset of illness. The case-fatality rates range from 3 to 30 percent; disseminated intravascular coagulation and vascular dysregulation are common in severe cases [14].

Ultrasound findings include hepatosplenomegaly, paraceliac lymphadenopathy, gallbladder wall thickening, and intraperitoneal and pleural effusion [16]. These become prominent on the third day of disease in some patients.

Viral isolation needs to be conducted in biosafety level four laboratories [13]. IgM and IgG antibodies are detectable by ELISA and immunofluorescence assays from about seven days after the onset of disease [17]. Specific IgM antibodies decline to undetectable levels approximately four months after presentation.

Treatment is mainly supportive. Ribavirin has been demonstrated to be effective in observational clinical studies [14,18]. Patients should be treated for 10 days (30 mg/kg as an initial loading dose, then 15 mg/kg every six hours for four days, and then 7.5 mg/kg every eight hours for six days) [13].

Case-fatality rates range from 3 to 30 percent; disseminated intravascular coagulation and vascular dysregulation are commonly seen in severe cases [14]. Higher serum levels of proinflammatory cytokines interleukin (IL-) 6 and tumor necrosis factor (TNF) were demonstrated in patients with fatal infection than in those who survived [19].

African trypanosomiasis — African trypanosomiasis (sleeping sickness) is endemic throughout much of Central Africa. Countries with the highest endemicity include Angola, Cameroon, Central African Republic, Chad, Congo, Democratic Republic of Congo, South Sudan, and Sudan. (See "Human African trypanosomiasis: Treatment and prevention" and "Human African trypanosomiasis: Epidemiology, clinical manifestations, and diagnosis".)

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 [20].

Leishmaniasis — Both cutaneous and visceral leishmaniasis occur in relatively restricted areas of South Sudan and Sudan. Sand flies of the genus Phlebotomus are the vectors. Visceral leishmaniasis occurs both sporadically and in epidemics. The main reservoirs are rodents and small carnivores. (See "Cutaneous leishmaniasis: Epidemiology and control" and "Visceral leishmaniasis: Epidemiology and control".)

Onchocerciasis — Onchocerciasis (river blindness) is caused by the roundworm Onchocerca volvulus and is transmitted to humans by Simulium black flies. Endemic areas are widespread through parts of Central 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 [21,22]. (See "Onchocerciasis".)

Rickettsioses — Several rickettsioses are endemic in Central Africa [23]. Environments suitable for transmission of both epidemic typhus (caused by Rickettsia prowazekii) and murine typhus (caused by Rickettsia typhi) are present in Central Africa. Epidemic typhus is transmitted by the body louse. Conditions that favor the proliferation of lice include crowding in the setting of 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 [24].

Chikungunya fever — Chikungunya fever has been increasingly reported in the region [25], with outbreaks in Chad, Congo, and Sudan. 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 Central Africa [26-29]. 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 is discussed further separately. (See "Zika virus infection: An overview".)

FOODBORNE AND WATERBORNE DISEASES

Travelers' diarrhea — Central Africa is a high-risk area for the development of travelers' diarrhea. Enterotoxigenic Escherichia coli is the most common pathogen identified [30]. (See "Travelers' diarrhea: Epidemiology, microbiology, clinical manifestations, and diagnosis".)

Cholera — Cholera outbreaks are frequent occurrences in Central Africa. (See "Cholera: Epidemiology, clinical features, and diagnosis".)

Typhoid — Typhoid fever is endemic throughout most of Central Africa, although the risk is generally less than in South Asia. (See "Enteric (typhoid and paratyphoid) fever: Epidemiology, clinical manifestations, and diagnosis" and "Enteric (typhoid and paratyphoid) fever: Treatment and prevention" and "Immunizations for travel", section on 'Typhoid vaccine'.)

Hepatitis A and E — Hepatitis A virus is endemic throughout Central Africa. Hepatitis E has been responsible for both outbreaks and sporadic cases of hepatitis [31]. (See "Hepatitis A virus infection in adults: Epidemiology, clinical manifestations, and diagnosis" and "Immunizations for travel", section on 'Hepatitis A vaccine' and "Hepatitis E virus infection".)

Schistosomiasis — Schistosomiasis due to Schistosoma haematobium and Schistosoma mansoni is widespread in Central Africa [32]. Transmission occurs through exposure to fresh water (lakes and slow-moving rivers) in endemic regions. (See "Schistosomiasis: Epidemiology and clinical manifestations".)

Paragonimiasis — Endemic foci of the lung fluke Paragonimus westermani are present in West and Central Africa. (See "Paragonimiasis".)

Dracunculiasis — Guinea worm (Dracunculus medinensis) infection was prevalent in the Central African region, but numbers of reported cases have fallen dramatically over years. A total of 54 cases were reported in 2019, all from Central Africa: Angola, Chad, South Sudan, and Cameroon [33]. The disease is associated with 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 "Echinococcosis: Clinical manifestations and diagnosis".)

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 [34]. (See "Global epidemiology of HIV infection".)

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

Hepatitis B and C — Hepatitis B virus is highly endemic throughout Central 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 sub-Saharan Africa. (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 Central Africa and has been reported with increasing frequency [35]. 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 Central 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 Central Africa, although short-term travelers from countries of low endemicity are generally not considered at increased risk of infection.

OTHER HAZARDS

Snake bites — Venomous snakes are present throughout Central 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".)

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

Central Africa is comprised of Angola, Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea, Gabon, South Sudan, Sudan, Democratic Republic of Congo (Zaire), and Zambia. This region encompasses tropical rain forests, desert areas, and wooded areas. (See 'Introduction' above.)

Malaria is a major risk for travelers to Central Africa. Endemic areas exist in all countries in this region. Plasmodium falciparum is the predominant cause of malaria, and chloroquine resistance is widespread. Within endemic areas, transmission occurs year round. (See 'Malaria' above.)

Other arthropod-borne diseases include yellow fever, dengue, African trypanosomiasis, leishmaniasis, onchocerciasis, and rickettsioses. Other viral hemorrhagic fevers include Ebola virus, Marburg virus, and Crimean-Congo hemorrhagic fever. (See 'Arthropod-borne diseases' above.)

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

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