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

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.

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.

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 × 10(5) plaque-forming units per milliliter [pfu/mL]; range, 1.3 × 10(1) -2.9 × 10(8) pfu/mL) were higher than but not significantly different from those observed in the viremic asymptomatic individuals (median, 3.4 × 10(3) pfu/mL; range, 8.4 × 10(1) -2.9 × 10(5) pfu/mL [p = 0.22, Wilcoxon test]).

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.