BACKGROUND: Dengue fever and hemorrhagic disease are caused by four dengue virus (DENV) serotypes (DENV-1 to -4), mosquito-borne flaviviruses with increasing incidence, and expanding global distributions. Documented transfusion transmission of West Nile virus raised concern regarding transfusion-transmitted DENV.

METHODS: A DENV RNA assay was developed based on transcription-mediated amplification (TMA) blood screening assays routinely used by blood centers worldwide. Sensitivity was established by endpoint dilution analyses of DENV-1 RNA transcript and pedigreed tissue culture standards for all four DENV-serotypes. Frozen plasma samples were tested from 2994 donations from Honduras (September 2004-January 2005), 4858 donations from Brazil (February-April 2003), and 5879 donations from Australia (March-September 2003). Type-specific polymerase chain reaction (PCR) assays were used to quantify and genotype TMA repeat-reactive samples; viral cultures, type-specific antibody, and antigen assays were also performed.

RESULTS: The TMA assay detected 14.9 copies per mL DENV-1 transcript (95% detection limit), with comparable sensitivity for all four serotypes. Honduran donors yielded 9 TMA repeat-reactive samples (0.30%); 8 were confirmed by PCR, with 3 DENV serotypes detected and viral loads from fewer than 3 × 104 to 4.2 × 104 copies per mL; and 4 samples yielded infectious virus. Three (0.06%) Brazilian samples tested repeat-reactive; 2 (0.04%) were PCR-positive (serotypes DENV-1 and -3; 12 and 294 copies/mL). No Australian donor samples tested repeat-reactive.

CONCLUSION: Dengue viremia rates among asymptomatic blood donors ranged from 0.30 percent in Honduras to 0.04 percent in Brazil. Future studies are needed to establish rates of transfusion transmission by viremic donations and clinical consequences in recipients.