Dengue Fever

Dengue fever and dengue hemorrhagic fever (DHF) are viral diseases transmitted by Aedes mosquitoes, usually Ae. aegypti. The four dengue viruses (DEN-1 through DEN-4) are immunologically related, but do not provide cross-protective immunity against each other.

This infectious disease is manifested by a sudden onset of fever, with severe headache, muscle and joint pains (myalgias and arthralgias — severe pain gives it the name break-bone fever or bonecrusher disease) and rashes; the dengue rash is characteristically bright red petechia and usually appears first on the lower limbs and the chest - in some patients, it spreads to cover most of the body. There may also be gastritis with some combination of associated abdominal pain, nausea,vomiting or diarrhea.

The World Health Organization considers dengue to be the most important vector-borne viral disease, potentially affecting 2.5 billion people in more than 100 tropical and sub-tropical countries throughout the world . Current estimates suggest that up to 50 to 100 million dengue cases occur annually, in addition to 500,000 cases of the more serious dengue hemorrhagic fever (DHF). DHF has a 5% case-fatality rate in many countries, with most fatalities occurring among children and young adults.

HEPATITIS B

Risk:

The risk of Hepatitis B virus infection is high for Central Africa. The risk to the individual international traveler is determined by the extent of: (1) direct contact with blood or other body fluids, etc.; (2) intimate sexual contact with an infected person; (3) the duration of travel.

Prevention:

The primary prevention consists of either vaccination and/or reducing intimate contact with those suspected of being infected. For those travelers expecting to reside in countries of high risk, as well as all health workers, vaccination is strongly recommended. Vaccination should ideally begin 6 months before travel, in order to complete the full series.

DISEASES TRANSMITTED THROUGH INTIMATE CONTACT

AIDS / HIV

Risk:

AIDS is found throughout the region. In Central Africa, heterosexual transmission accounts for the majority of the cases, with men and women more of less equal. In addition, many women of child bearing age are infected, and HIV transmission from mother to infant is widespread. The risk to a traveler depends on whether the traveler will be involved in sexual or needle-sharing contact with a person who is infected with HIV. Receipt of unscreened blood for transfusion poses a risk for HIV infection.

Prevention:

No effective vaccine has been developed for HIV. Travelers should avoid sexual or needle-sharing contact with a person who is infected with HIV. If a blood transfusion is necessary, screened blood should be from an HIV-negative blood donor.

HEPATITIS A

Risk: Travelers are at high risk for Hepatitis A, especially if travel plans include visiting rural areas and extensive travel in the countryside, frequent close contact with local persons, or eating in settings of poor sanitation. A study has shown that many cases of travel-related hepatitis A occur in travelers to developing countries with "standard" itineraries, accommodations, and food consumption behaviors.

Prevention:

The virus is inactivated by boiling or cooking to 85 degrees centigrade for one minute, therefore eating thoroughly cooked foods and drinking only treated water serve as general precautions. Havrix, the hepatitis A vaccine currently licensed for use in the U.S., or immune globulin (IG) is recommended before travel for persons 2 years of age or older. Hepatitis A vaccine is preferred for persons who plan to travel repeatedly or reside for long periods of time in intermediate or high risk areas. Immune globulin is recommended for travelers <>

CHOLERA

Risk:

Cholera cases have been reported from most of the countries of Central Africa. The risk of infection to the U. S. traveler is low, especially those that are following the usual tourist itineraries and staying in standard accommodations. Travelers should consider the vaccine if they have stomach ulcers, use anti-acid therapy, or if they will be living in less than sanitary conditions in areas of high cholera activity.

Prevention:

Travelers to cholera infected areas should follow the standard food and water precautions of eating only thoroughly cooked food, peeling their own fruit, and drinking either boiled water, bottled carbonated water, or bottled carbonated soft drinks. Persons with severe cases respond well to simple fluid and electrolyte-replacement therapy, but medical attention must be sought quickly when cholera is suspected. The available vaccine is only 50% effective in reducing the illness, and is not recommended routinely for travelers.

Food and Waterborne Diseases

Make sure your food and drinking water are safe. Food and waterborne diseases are the primary cause of illness in travelers. Travelers´diarrhea can be caused by viruses, bacteria, or parasites, which are found throughout West Africa and can contaminate food or water. Infections may cause diarrhea and vomiting (E. coli, Salmonella, cholera, and parasites), fever (typhoid fever and toxoplasmosis), or liver damage ( hepatitis).

Yellow Fever

Yellow fever is a viral disease that is transmitted to humans through the bite of infected mosquitoes. Illness ranges in severity from an influenza-like syndrome to severe hepatitis and hemorrhagic fever. The yellow fever virus is maintained in nature by mosquito-borne transmission between nonhuman primates. Transmission by mosquitoes from one human to another occurs during epidemics of "urban yellow fever."

Risk for Travelers

A traveler's risk of acquiring yellow fever is determined by immunization status, location of travel, season, duration of exposure, occupational and recreational activities while traveling, and the local rate of yellow fever virus transmission at the time. Although reported cases of human disease are the principal indicator of disease risk, they may be absent (because of a high level of immunity in the population) or not detected as a result of poor surveillance. Only a small proportion of yellow fever cases are officially reported because of the occurrence of the disease in remote areas and lack of specific diagnostic facilities.

During interepidemic periods, low-level transmission may not be detected by public health surveillance. Such interepidemic conditions may last years or even decades in certain countries or regions. This "epidemiologic silence" may provide a sense of false security and lead to travel without the benefit of vaccination. Surveys in rural West Africa during "silent" periods have estimated an incidence of yellow fever of 1.1-2.4 cases per 1,000 persons and an incidence of death due to yellow fever of 0.2-0.5 deaths per 1,000 persons; both these ranges are less than the threshold of detection of the surveillance systems in place.

The incidence of yellow fever in South America is lower than that in Africa because the mosquitoes that transmit the virus between monkeys in the forest canopy do not often come in contact with humans and because immunity in the indigenous human population is high. Urban epidemic transmission has not occurred in South America for many years, although the risk of introduction of the virus into towns and cities is ever present. For travelers, the risks of illness and death due to yellow fever are probably 10 times greater in rural West Africa than in South America; these risks vary greatly according to specific location and season. In West Africa, the most dangerous time of year is during the late rainy and early dry seasons (July-October). Virus transmission is highest during the rainy season (January-March) in Brazil.

MALARIA

Malaria is always a serious disease and may be a deadly illness.
Humans get malaria from the bite of a mosquito infected with the parasite. Your risk of malaria may be high in all countries in Central Africa, including cities. All travelers to Central Africa, including infants, children, and former residents of Central Africa, may be at risk for malaria. Prevent this serious disease by seeing your health care provider for a prescription antimalarial drug and by protecting yourself against mosquito bites. All travelers should take one of the following drugs:
atovaquone/proguanil,
doxycycline,
mefloquine, or
primaquine (in special circumstances).