Brazil is one of the countries which has been most affected by dengue epidemics. This scenario became more challenging with the emergence of Zika virus after 2014. The cocirculation of dengue and Zika viruses makes their diagnosis and treatment a challenge for health professionals, especially due to their similar clinical outcomes. From 2015 to 2019, we followed a cohort of 2017 participants in Goiania, Goias, Central Brazil. Febrile cases were monitored weekly, and after identification of fever, the physician performed a home visit for clinical evaluation and collection of blood/urine for diagnosis of acute dengue/Zika infection in suspected cases. Dengue acute infection was investigated by NS1 antigen and real time RT-PCR and seroconversion of anti-dengue IgM. ZIKV infection was confirmed by real time RT-PCR. Six cases of Zika/dengue coinfection among participants were reported. The clinical outcomes were suggestive for both DENV and ZIKV infection. No coinfected patient had neurological clinical manifestation, warning signs or need for hospitalization. A continuous specific laboratory confirmation for both dengue and Zika viruses should be enforced as part of the surveillance systems even in the presence of very suggestive cases of dengue fever, minimizing the risk of a late detection of ZIKV circulation.

Dengue is considered the most important acute febrile arbovirus in the world due to its burden on morbidity and mortality of countries. Cohort studies are appropriate for understanding dengue transmission dynamics and establishing baselines prior to the adoption of new control strategies. However, these studies pose major operational challenges that tend to hinder their execution, especially in developing countries. The strategies used in implanting and conducting a cohort in Central Brazil (city of Goiania) are presented, including the approaches adopted to overcome the challenges observed. The following steps are described and discussed: defining the field work team, establishing partnerships and the recruitment of participants; the initial serosurvey; technology in field research; and monitoring and evaluation of febrile episodes. A partnership between academia and public health services was the adopted approach and participation of the Municipal Health Secretariat and the Family Health Teams was essential for the proper implementation and conduction of the study. In return, the researchers' performance favored the Health Service through surveillance and health care activities of the population. This interinstitutional experience was successful with benefits for both institutions.