Insects Chagas Disease. A disease caused by a parasite which is transmitted to humans through certain blood-sucking bugs. Once infected, a person may have no symptoms for many years. In a minority of people, delayed chronic symptoms emerge years later because infections of the heart develop in 20-30% of cases; intestinal complications in less than 10%; and nerve damage in 2-3% of cases. Dengue Fever. This illness and a more severe form called dengue hemorrhagic fever (DHF) are caused by four closely related dengue viruses that are transmitted by mosquitoes. Infection with any of these viruses can cause fever, rash, and body aches, or in the case of DHF, a syndrome of leaking capillaries and a sudden worsening of overall condition. Once a person is infected with one type of virus, he or she is usually immune from reinfection with the same type. However, protection doesn't extend to the other three types, so a person could have more than one episode of dengue in a lifetime. Filariasis. A group of diseases caused by insect-transmitted roundworms called "filaria." Worm larvae that enter during an insect bite can migrate within a person's body. In about nine months, the larvae mature into adults that live mainly in the lymph nodes of the groin and armpit. Filariasis can damage the lymphatic system, and in some cases cause elephantiasis, a grotesque swelling of the skin and tissues, sometimes in the arms or breasts, but more commonly in the legs or scrotum. Hookworm. A small roundworm with a remarkable life cycle: the microscopic larvae penetrate human skin and enter blood vessels that carry them to the lungs. They stop in the lungs, penetrate through the lung tissue to the airways, then crawl over the back of the throat until they are swallowed into the intestines. In the bowels, they mature into adult worms, feed on blood from the intestinal walls, and start laying eggs. If a person has chronic hookworm infection, symptoms include anemia, weakness, coughing and diarrhea. When the person passes hookworm eggs out with the stool and onto the ground, the larvae hatch over a five to ten day period. The roundworm's life cycle begins again, and new human infections occur. Japanese Encephalitis. Caused by a virus that is transmitted in rural areas of Asia. Domestic pigs and wild birds serve as its natural hosts, and certain mosquitoes can transmit the virus to humans. Infection can occur throughout the year in tropical areas of Asia, with epidemics in late summer possible in more temperate regions. Local people may have a high rate of infection without symptoms. Of all people who become ill with JE, about one-third die, one-third suffer permanent brain injury, and one-third recover completely. Leishmaniasis. An infection by any of a large number of infectious parasites and transmitted by sandfly bites. The parasites live inside cells of several hosts including humans, dogs, rodents, and other small animals. Depending on their particular form, the parasites may prefer cells in the skin (cutaneous leishmaniasis), mucous membranes (mucocutaneous leishmaniasis), or internal organs (visceral leishmaniasis). Infections of the skin and mucous membranes typically exist at a low, steady rate in affected regions, but the visceral form can erupt in epidemics affecting tens of thousands of people. Lyme Disease. An infection caused by bacteria that are transmitted by the bite of certain species of ticks. There is usually a characteristic "bull's eye rash" at the site of the bite, often with fever, fatigue, headache, and joint and muscle pain. If left untreated, Lyme disease may lead to severe arthritis and neurological or heart problems. Malaria. A disease caused by a parasite carried by certain mosquitoes. Plasmodium falciparum causes the most severe infections, which can often be fatal. Plasmodium vivax causes a lower-grade infection that is rarely fatal, but can occur long after the person has left the malaria risk area. Plasmodium ovale and Plasmodium malariae are rarely diagnosed in travelers. Travelers are at higher risk of severe malaria infection, because people living in a malaria region gradually develop a partial degree of immunity. Onchocerciasis or River Blindness. Caused by parasitic worms that are transmitted by the black-fly bites. The worms enter the blood as microscopic larva, and grow into adults in nodules under the skin. Female worms release large numbers of microscopic larvae that migrate through the tissues under the skin. The most severe symptom of the disease is blindness. Plague. A disease caused by bacteria that infect wild rodents, whose fleas can pass the illness to humans and other mammals. Humans contract the disease either through the bite of an infected flea (bubonic plague), or after being exposed to coughing and sneezing from an infected person (pneumonic plague). Bubonic plague is characterized by large infected lymph nodes. Pneumonic plague develops rapidly and has a higher fatality rate. Relpasing Fever. A disease caused by one of several bacteria. Louse-borne relapsing fever involves only one species of bacteria and is transmitted from person to person by lice. Tick-borne relapsing fever is caused by at least 15 species of bacteria and is transmitted to humans by ticks from infected rodents and small animals. The disease gets its name from the fact that after an initial illness of three to six days, the symptoms disappear for seven to 10 days before suddenly recurring. Multiple relapses can occur over a period of time. It is a potentially fatal disease, but there is a great deal of variation in how severe the illness can be, ranging from no symptoms to severe symptoms. The louse-type is usually more serious than the tick-borne form. Tick-borne Encephalitis (TBE). A viral illness that is named for its transmission by infected ticks. It can infect the central nervous system, resulting in serious illness from meningitis or encephalitis (inflammation of the brain and its surrounding membranes). There are two different strains of TBE corresponding to the two main geographic areas of infection, European and Far Eastern. The Far Eastern variety more often causes serious illness or death. Tick-borne encephalitis is a risk only to people living in endemic areas or to tourists to these areas with activities that bring them in contact with ticks. Fortunately, only one out of 250 people who get infected with the virus actually becomes ill. Trypanosomiasis or Sleeping Sickness. A chronic progressive illness caused by parasites that are transmitted by the tsetse fly. The late stages of the illness are characterized by increasing sleepiness, leading to eventual coma and death--hence the name "sleeping sickness." Yellow Fever. An infectious disease caused by the yellow fever virus, which is transmitted by mosquitoes. The virus is related to the dengue virus. About five to 20% of people infected with yellow fever will develop temporary liver damage that leads to jaundice and a yellowing of the eyes and skin—hence the disease"s name. About 20% of people who develop jaundice will die.

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