because they already had or rapidly developed immune responses that controlled the disease, or because they had another, self-limiting disease such as the flu rather than malaria. Some patients for various reasons do not improve, and either return for more definitive care or seek help from other sources (traditional local treatments or over-the-counter medications). Some may worsen and die, although this progression cannot be assumed, especially in a semi-immune population.

Most travelers who contract malaria initially develop the uncomplicated form of the disease. In a nonimmune patient, however, the progression to severe malaria is often very rapid. When the circumstances are appropriate, both patients and their doctors should be alert to the possibility of malaria infection and should treat the disease as a medical emergency. As is true for all malaria patients, the choice of drug treatment for travelers depends on the species of malaria parasite involved, where the infection was contracted (parasite drug sensitivities vary substantially around the world), what (if any) malaria chemoprophylaxis was used, and the pertinent details of the individual's medical history (World Health Organization, 1990).

Malaria Chemoprophylaxis and Treatment

Nonimmune visitors to malaria-endemic areas are at risk for developing severe and complicated malaria and therefore benefit from a regimen of preventive drug therapy. In the past, chloroquine chemoprophylaxis was effective and safe and was recommended for all who were at risk of acquiring the disease. The spread of chloroquine-resistant P. falciparum and P. vivax (Rieckmann et al., 1989), however, has complicated matters, particularly since each of the currently available alternatives to chloroquine has some toxicity. Mefloquine is the latest addition to the antimalarial armamentarium (Department of Health and Human Services, 1990).

There is no consensus regarding the optimal chemoprophylactic regimen for persons living in or visiting the range of locales in which malaria infection is possible (Bradley and Phillips-Howard, 1989; Department of Health and Human Services, 1990). It is important for both travelers and physicians to realize that no prophylactic regimen is completely effective in all cases and that rapid diagnosis and prompt treatment are important.

Pregnant women living in endemic areas constitute another group for which malaria chemoprophylaxis has been recommended. Babies born to first-time mothers with malaria often weigh less than babies born to uninfected mothers (Brabin, 1983; McGregor, 1984). Malaria can also cause severe anemia in women during their first pregnancy (Gilles et al., 1969; Brabin, 1983; McGregor, 1984). Although women living in malaria-endemic areas frequently receive chemoprophylaxis during pregnancy, few studies have

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