Con- selho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) and Fundacao Nacional de Desenvolvimento do Ensino Superior Particular (FUNADESP). The authors are grateful to Andris K. Walter for English language revision and copyediting services.Several major epidemics of Zika fever, caused by the ZIKA virus (ZIKV), have emerged in Brazil since early 2015, eventually spreading to other countries on the South American con- tinent. The present study describes the clinical manifestations and laboratory findings of patients with confirmed acute ZIKV infection during the first epidemic that occurred in Sal- vador, Brazil. All included patients were seen at the emergency room of a private tertiary hospital located in Salvador, Brazil from 2015 through 2017. Patients were considered eligible if signs of systemic viral febrile disease were present. All individuals were tested for ZIKV and Chikungunya infection using PCR, while rapid test was used to detect Dengue virus anti- bodies or, alternatively, the NS1 antigen. A diagnosis of acute ZIKV infection was confirmed in 78/434 (18%) individuals with systemic viral febrile illness. Positivity was mainly observed in blood, followed by saliva and urine. Coinfection with Chikungunya and/or Dengue virus was detected in 5% of the ZIKV-infected patients. The most frequent clinical findings were myalgia, arthralgia and low-grade fever. Laboratory analysis demonstrated normal levels of hematocrit, platelets and liver enzymes. In summary, in acute settings where molecu- lar testing remains unavailable, clinicians face difficulties to confirm the diagnosis of ZIKV infection, as they rely only on clinical examinations and conventional laboratory tests