doi:10.4269/ajtmh.13-0077 Copyright © 2014 by The American Society of Tropical Medicine and Hygiene Short Report: Investigation of Dengue and Japanese Encephalitis Virus Transmission

Abstract. This study investigated whether a large dengue epidemic that struck Hanoi in 2009 also affected a nearby semirural area. Seroconversion (dengue virus-reactive immunoglobulin G enzyme-linked immunosorbent assay) was high during 2009 compared with 2008, but neutralization assays showed that it was caused by both dengue virus and Japanese encephalitis virus infections. The findings highlight the importance of continued Japanese encephalitis virus vaccination and dengue surveillance. Dengue is an emerging health problem in northern Viet Nam, and in Hanoi, the capital, the largest recorded outbreak occurred in 2009, when 16,175 clinical cases were reported.1 Clinical dengue incidence in northern Viet Nam is highest in urban Hanoi, and transmission commences around July, sev-eral months after the end of winter, and ceases in late Decem-ber,1 coinciding with changes in vector abundance.2 Dengue cases have been detected sporadically in other northern prov-inces of Viet Nam,3 and 11 % of dengue patients presenting to a Hanoi hospital during 2008 had come from other provinces.