Of importance was the reintroduction of dengue virus in
Brazil, which occurred during the mid-1980s and reached the
state of Rio Grande do Norte in the late 1990s. Leptospirosis
has an overlapping clinical presentation with that of dengue;
often it is difficult if not impossible to differentiate the two
diseases based on clinical findings. In the Americas, there
is growing evidence that leptospirosis is frequently misdiagnosed
as dengue (Bruce et al., 2005; Flannery et al., 2001b;
Ko et al., 1999; Levett et al., 2000). In the study community,
outbreaks of suspected dengue have been reported since
2001, as shown in Figure 1. It is conceivable that a proportion
of these cases may have been, in fact, due to leptospirosis.
Under-reporting of leptospirosis cases due to diagnostic
confusion with dengue may be a possible explanation for
the relatively high prevalence of prior Leptospira infection
observed in this study, which occurred during a period when
cases of leptospirosis were not identified. Finally, the diagnostic
dilemma created by the re-emergence of dengue in
the Americas underscores the importance of implementing
laboratory-based surveillance for acute febrile illnesses in
the region and extending diagnostic support to neglected
rural regions, where transmission of dengue and leptospirosis
has become endemic.