  For decades, dengue virus has been a cause of major public health concern in
Costa Rica, due to its landscape and climatic conditions that favor the
circumstances in which the vector, Aedes aegypti, thrives. The emergence and
introduction throughout tropical and subtropical countries of the chikungunya
virus, as of 2014, challenged Costa Rican health authorities to provide a
correct diagnosis since it is also transmitted by the same vector and infected
hosts may share similar symptoms. We study the 2015-2016 dengue and chikungunya
outbreaks in Costa Rica while establishing how point estimates of epidemic
parameters for both diseases compare to one another. Longitudinal weekly
incidence reports of these outbreaks signal likely misdiagnosis of infected
individuals: underreporting of chikungunya cases, while overreporting cases of
dengue. Our comparative analysis is formulated with a single-outbreak
deterministic model that features an undiagnosed class. Additionally, we also
used a genetic algorithm in the context of weighted least squares to calculate
point estimates of key model parameters and initial conditions, while formally
quantifying misdiagnosis.
