Clinical symptoms and Zika viral loads in blood donors. The distribution of symptomatic donors according to time of inaugural symptoms (A) and the frequency of reported symptoms (B) are presented. Zika viral loads (log₁₀ copies/mL) are provided in both asymptomatic and symptomatic blood donors (C). Zika viral load was determined by real-time reverse transcription polymerase chain reaction in 41 donors reporting clinical signs, and 34 donors who did not. The diagram reports for each series the quantitative distribution of viral load, together with the median value ± SD.