To the Editor: Dengue, the most common vectorborne viral infection worldwide,1 is predominantly transmitted by the Aedes aegypti mosquito. We describe a well-documented cluster of blood transfusion–associated dengue infections in Singapore, a country in which the disease is endemic. A 52-year-old, asymptomatic, repeat blood donor gave blood on July 15, 2007. An investigation of all recipients of his blood products was initiated after he informed the blood bank that he had had a fever the day after donation. The stored serum sample was positive for dengue virus type 2, as ascertained by means of a polymerase-chain-reaction (PCR) assay.2 The recipient . . .