Risk for malaria in United States donors deferred for travel to malaria-endemic areas.

Background: Deferral for travel to malaria-endemic areas excludes many blood donors in the United States. Most transfusion-transmitted malaria is associated with lengthy residence in malaria-endemic areas rather than routine travel. This study compares the impact of existing deferral requirements to the risk that a presenting donor with malaria travel history harbors malaria parasites under current and hypothetical alternate regulations.

Study Design And Methods: Deferred donors from six blood centers were sampled to estimate a national cohort of donors deferred annually for malaria travel to different geographic regions. Risk for malaria infection after travel to each region and distribution of incubation periods for each malaria species were estimated for US travelers. Region-specific travel risks were used to estimate the risk that a presenting blood donor with malaria travel might asymptomatically harbor malaria parasites at different intervals after return to the United States.

Results: Travel to Africa presents risk for malaria infection greater than 1000 times that of travel to malaria-endemic parts of Mexico, yet Mexico accounts for more than 10 times as many deferred donors. Shortening the deferral period from 12 to 3 months for travelers to Mexico increases the risk of collecting a contaminated unit by only 1 unit per 57 years (sensitivity analysis, 1 every 29-114 years), at annual gain of more than 56,000 donations.

Conclusion: This study provides the first systematic appraisal of the US requirements for donor qualification regarding travel to malarial areas. Consideration should be given to relaxing the guidelines for travel to very-low-risk areas such as Mexico.