Other Infectious Diseases The international traveler may be potentially exposed to infectious diseases for which no vaccines or preventive medications are currently available. The following includes a brief description of selected infectious diseases and appropriate precautions that may be of interest to international travelers. African sleeping sickness | Amebiasis | American trypanosomiasis | Dengue fever | Lassa fever | Leishmaniasis | Onchocerciasis | Rift Valley fever | Schistosomiasis | Sexually transmitted diseases | Tickborne encephalitis African sleeping sickness (African trypanosomiasis) is transmitted by the bite of the tsetse fly, a large gray-brown insect approximately the size of a honeybee, which bites during the day. Fever, rash or skin lesions, lethargy, and confusion are usually the predominate signs and symptoms. Travelers at risk should take personal protective measures against these flies. Amebiasis is caused by a protozoan parasite. Infection is acquired by the fecal-oral route, either by person-to-person contact or indirectly by eating or drinking fecally contaminated food or water. Most infected persons do not have symptoms. In persons with symptoms, diarrhea is most common. Travelers at risk are advised to take appropriate food and beverage precautions. American trypanosomiasis (Chagas' disease) is caused by a protozoan parasite that is usually transmitted by contact with the feces of an infected reduviid bug. Transmission may also occur through blood transfusion or via transplacental infection. Acute infection may be asymptomatic or accompanied by a fever with inflammation of the heart muscle or the lining of the brain or spinal cord. Travelers at risk should take personal protective measures against these bugs. Dengue fever and dengue hemorrhagic fever are viral diseases transmitted by urban Aedes mosquitos that feed on humans during the daytime. Many cases of subclinical or nonspecific infection occur, but dengue may also present as a severe and fatal hemorrhagic disease. Dengue fever is characterized by sudden onset, high fever, severe frontal headache, and joint and muscle pain. Many patients have nausea, vomiting, and rash. Travelers at risk should take personal protective measures against these mosquitos. Lassa fever is a severe, often fatal, hemorrhagic fever that occurs in rural areas of West Africa, and is caused by a virus transmitted from infected rodents to man. The risk of infection in international travelers is considered small. Leishmaniasis is a parasitic disease acquired through the bite of some species of sand flies. The disease most commonly manifests either in a cutaneous (skin) form or in a visceral (internal organ) form. The appearance of disease in the cutaneous form may take weeks to months after infection, while the visceral form may take months to years to develop. Preventive measures include reducing contact with sand flies and taking personal protective measures against them. Onchocerciasis (river blindness) is transmitted by the bite of female Simulium flies (black flies) that bite during the day and are found near rapidly flowing rivers and streams. The disease may result in skin lesions, swollen glands, and visual impairment, including blindness. Infections tend to occur in expatriate groups such as missionaries and their families, field scientists, and Peace Corps volunteers. Preventive measures include avoidance of black fly habitats and use of personal protective measures against them. Rift Valley fever is a viral disease transmitted by the bites of mosquitos and other biting insects, and by skin inoculation or inhalation of aerosols from contaminated blood or fluids of infected animals. Disease manifestations may include fever with headache, fatigue, and muscle or joint pain. More severe infections may also result in encephalitis, hemorrhage, or blindness. Travelers visiting risk areas can reduce their exposure by avoiding contact with livestock and taking personal protective measures against mosquitos and other biting insects. Schistosomiasis (bilharziasis) is caused by flukes whose complex life cycles utilize specific fresh water snail species as intermediate hosts. Schistosomiasis infection is estimated to occur among 200 million persons worldwide. The most common acute symptoms include fever, weakness, headache, and it may affect the gastrointestinal system. Chronic infections can cause disease of the lungs, liver, intestines, or bladder. Even brief exposures to contaminated water can result in infection. Those at greatest risk are travelers who engage in wading or swimming in fresh water in rural areas where poor sanitation and appropriate snail hosts are present. Bathing with contaminated fresh water can also transmit infection. Schistosomiasis is not acquired by wading or swimming in salt water (oceans or seas). Travelers to risk areas should take swimming precautions and treat bath water by heating it to 122 degrees F for five minutes or by treating it with iodine or chlorine (see food and beverage precautions) to make it safe. In case of accidental water exposure, vigorous towel drying is suggested as a possible mechanism to interrupt skin penetration and infection. Sexually transmitted diseases including HIV infection and AIDS, are caused by numerous infectious agents. Travelers should be aware that the risk of sexually transmitted disease is very high in certain parts of the world. If treatment does exist, it may be complicated by the emergence of antibiotic-resistant strains of disease. To avoid acquiring sexually transmitted diseases, travelers should not have sexual contact with persons who may be infected. Persons most likely to be infected include those with numerous sex partners, such as prostitutes. Travelers choosing to have sexual contact may reduce their risk of acquiring infection by always using a latex condom during intercourse. Tickborne encephalitis is a viral infection of the central nervous system transmitted by bites of certain vector ticks. Risk of acquiring the disease is greater from April through August. Infections follow bites of infected ticks, usually in travelers who visit forests, fields, or pastures. Infection may also be acquired by consuming unpasteurized dairy products from infected cows, goats, or sheep. Travelers to risk areas should take personal preventive measures against ticks and avoid consumption of unpasteurized dairy products.