Viremic profiles in asymptomatic and symptomatic chikungunya fever: a blood transfusion threat?

Background The presence of a chikungunya virus (CHIKV) outbreak could have an impact on transfusion safety when there are a large number of infected persons during an epidemic. Serosurveys have found that 3% to 28% of infected persons remain asymptomatic and are potential disseminators of transfusion‐associated chikungunya. However, the viremic profiles of asymptomatic chikungunya patients, the major determinant of the transfusion risk, are unknown. Study Design and Methods Data on CHIKV viremic profiles were obtained from a case‐control study carried out in a chikungunya‐affected area during the 2009 epidemic in Songkhla, Thailand. CHIKV‐infected individuals were classified based on a combination of the patient's history and clinical and laboratory findings. Results There were 134 laboratory‐proven CHIKV‐infected cases, of whom 122 (91.0%) were symptomatic and 12 (9.0%) were asymptomatic. The viremic levels in the symptomatic infected individuals peaked on the first 3 days and lasted up to 8 days as defined by viral isolates. CHIKV genomic products were detected as late as Day 17 of illness. The viral loads observed in the symptomatic individuals (median, 5.6 × 105 plaque‐forming units per milliliter [pfu/mL]; range, 1.3 × 101‐2.9 × 108 pfu/mL) were higher than but not significantly different from those observed in the viremic asymptomatic individuals (median, 3.4 × 103 pfu/mL; range, 8.4 × 101‐2.9 × 105 pfu/mL [p = 0.22, Wilcoxon test]). Conclusion CHIKV infection is highly symptomatic and is associated with high‐titred viremia. The viremic levels in asymptomatic CHIKV‐infected individuals were in the range known to be capable of transmitting the disease to experimental animals. Asymptomatic CHIKV viremia individuals could be potential disseminators of transfusion‐associated chikungunya.