Isolation of dengue virus serotype 1 from the blood of a Swiss traveler prior to seroconversion.

Dengue virus serotype 1 was isolated from the blood of a patient who had returned to Switzerland from Brazil with fever of unknown origin. After 2 days of culture on Aedes albopictus (C6/36) cell line, the dengue virus was identified as serotype 1 using a type-specific indirect immunofluorescence assay. The diagnosis was confirmed by seroconversion of anti-dengue virus-specific IgM and IgG antibodies and by amplification of a serotype 1-specific region of the dengue virus genome. This is the first description of dengue virus isolation from the blood of a traveler returning to Switzerland. We recommend detection of dengue viremia during the 1st week of illness, before serological tests usually yield conclusive results, as the most efficient means of early specific diagnosis.