A clinical, serological, and immunological study in a Japanese traveler with dengue fever

We describe the results of clinical, serological, and immunological studies in a Japanese traveler with dengue fever (DF). DF was confirmed by isolation of dengue virus from the serum, a positive direct reverse-transcription polymerase chain reaction (RT-PCR) test, and a high titer of anti-IgM antibody to dengue virus. Interestingly, in this patient infected by dengue virus serotype 3, we found a low CD4/CD8 ratio and a decrease in CD4 lymphocytes, a variation of cross-reaction to dengue virus serotypes 1, 2, and 4, and high serum interferon-gamma levels just after a transient elevation of interleukin-12.