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To measure the effectiveness and tolerance of long-term malaria prophylaxis with mefloquine, the incidence of Plasmodium falciparum malaria and of adverse reactions was compared in Peace Corps volunteers in West Africa who took mefloquine every 2 weeks and in volunteers who took chloroquine phosphate weekly. Mefloquine was only 63% more effective than chloroquine; the monthly incidence of P falciparum infections was one case per 100 volunteers who took mefloquine and 2.7 cases per 100 volunteers who took chloroquine. Using daily proguanil (chloroguanide) hydrochloride in addition to chloroquine did not provide additional protection. All mefloquine prophylaxis failures occurred during the second week of the every-2-weeks dosing regimen in volunteers who had used mefloquine for more than 2 months. Blood concentrations of mefloquine were lower during the second week of the alternate-week regimen than during the first week, suggesting that blood levels are too low during the second week to suppress parasitemia. No serious adverse reactions were observed. The results indicate that a dosing regimen of 250 mg of mefloquine weekly should be considered for travelers to areas with chloroquine-resistant P falciparum malaria.

Data from the US National Malaria Surveillance System were analyzed to assess characteristics of travelers who acquired Plasmodium falciparum infections in Africa and evaluate the impact of chloroquine resistance on the incidence of imported malaria. Although the number of cases acquired in East Africa has stabilized, the number of imported P falciparum infections acquired in West Africa increased threefold from 1985 to 1988, and the proportion of travelers who reported failure of chloroquine prophylaxis increased from 10% to 48%. Fifty-eight percent of patients who acquired malaria in West Africa had not used chemoprophylaxis. To curb the rising incidence of P falciparum infections in American travelers, the Centers for Disease Control revised malaria prophylaxis recommendations to include the use of mefloquine in areas of chloroquine resistance. Use of malaria protection measures by travelers to West Africa must also be improved.

A 48-year-old physician, who was not undergoing malaria chemoprophylaxis, contracted Plasmodium falciparum while working in eastern Thailand. In the hospital, he had a peak parasitemia of 72% RBCs infected, associated with CNS dysfunction. As an adjunct to chemotherapy, a double-volume whole-blood exchange transfusion was performed on the first hospital day, dropping the parasitemia to less than 1% within 32 hours. The patient's clinical condition improved, with a prompt reversal of CNS, hepatic, and renal complications. These results, combined with those in previously reported cases, suggest that exchange transfusion should be considered more generally as a life-saving procedure in P falciparum infections.

To better estimate rates of certain benefits and risks of recreational running, we sent questionnaires to 1,250 randomly selected male and 1,250 female registrants for a 10-km road race. The response rate was 55% for men and 58% for women. Telephone interviews of a randomly selected group of nonrespondents indicated that the only significant differences between respondents and nonrespondents were that (1) respondents were older than nonrespondents, (2) more male nonrespondents had stopped running during the year after the race, and (3) more male nonrespondents had been hit by thrown objects. One year after the race, 89% of male and 79% of female respondents were still running regularly. Eighty-one percent of men and 75% of women who smoked cigarettes when they began running had stopped smoking after beginning recreational running. Giving up smoking was significantly more common for current runners than for "retired" runners. Weight loss was commonly associated with running and was greater in those persons who were overweight when they began running. More than a third of respondents had a musculoskeletal injury attributed to running in the year after the race and about one seventh of all respondents sought medical consultation for their injury. The risk of injury increased with increasing weekly mileage. This study uses epidemiologic methods to quantify some of the benefits and risks of running.

The euthyroid autonomous nodule of the thyroid may escape diagnosis if only the usual criterion of less than 50% suppression of radioactive iodine uptake, (RAIU) after administration of liothyronine sodium is employed. This was the case in four patients who had thyrotoxic response to suppressive therapy, which had been given as a result of the improper conclusion that a nodule was hyperplastic, after the RAIU had fallen. We studied 95 patients with a solitary functioning nodule and found ten euthyroid persons (11 tests) in whom scintiscans showed persistent function in the nodule in spite of suppression of the RAIU by more than 50%. A thyrotropin-releasing hormone test demonstrated lack of thyroid-stimulating hormone responsiveness after administration of liothyronine, proving adequacy of the suppressive dose. Diagnosis of an autonomous nodule should not be excluded unless a scintiscan reveals that its function, in distinction to the rest of the gland, is curtailed by adequate suppression.