A survey of malaria in Indochinese refugees arriving in the United States, 1980.

Abstract During the months April–June and October–November 1980, a survey was conducted among Indochinese refugees arriving in California to assess the prevalence of malaria. During the two study periods, 3,433 refugees were met and 3,289 (95.8%) of the arriving refugees were screened for malaria by examining thick blood smears and by indirect fluorescent malaria antibody tests of blood absorbed on filter paper. Examination of the blood smears showed that the overall patency rates were 1.7% and 0.6% for the first and second surveys, respectively. The Cambodian refugees and refugees from camps in Thailand had the highest patency rate in the first survey. In the second survey, the Cambodian refugees and refugees from camps in Indonesia had the highest patency rate. The average malaria seropositivity rate was 15% in the first and 13.6% in the second survey. The Laotian refugees had the highest rate of malaria seropositivity in both surveys. Plasmodium vivax was the most commonly identified species in blood examination, while a higher rate of seropositivity to P. falciparum was found in both surveys. This study indicates that the malaria infection rate was at least 1.7% based on blood smear examination but might be as high as 45% based on serologic examinations. The results of this study when combined with malaria surveillance indicate that the likelihood of introduced malaria in the United States from the Indochinese refugees is low.