In previous studies, TNF-α has been reported to be associated with severity, mainly during DHF in Brazilian patients [11, 13, 41] . In the present study, however, this cytokine was not strongly associated with severity. Indeed, other authors also found inconsistency or no difference in TNF-α levels in severe vs. mild disease forms [10, 42] . We may hypothesize that differences in Dengue virus serotypes or in host immune response such as different TNF-α genetic polymorphisms may explain the disease outcome. In our study from 2001 (Braga et al., 2001) , patients were Dengue-2 infected, while in the present study, patients were Dengue-1 and -3 infected. A recent report [43] describes non-significant TNF-α serum levels in adult patients and suggests that the discrepancy may have been caused by a transient TNF-α peak which was not detected at a later time point.