Serologic evidence of dengue infection before onset of epidemic, Bangladesh.

Dengue fever emerged in Bangladesh in 2000. We tested 225 serum samples from febrile patients and 184 blood donors in 1996 and 1997 for dengue antibodies; 55 (24.4% ) febrile patients had dengue antibodies ( 65.5% with secondary infection pattern), compared with one (0.54%) donor (p <0.001), suggesting that dengue transmission was ongoing well before 1996.