Description of the first cases of Zika virus fever investigated in municipalities of the Brazilian Northeastern Region, 2015

to confirm Zika virus circulation and discard other etiological agents in an outbreak occurred in the states of Rio Grande do Norte, Maranhão and Paraíba, in May, 2015. this is a case series descriptive study with residents in Natal-RN, Barra do Corda-MA, São Luis-MA and João Pessoa-PB, with 20 cases in each state, presenting rash, absent or mild fever and one of the following signs/symptoms: conjunctival hyperemia, arthralgia or limb edema; RT-PCR/isolation tests for Zika, enterovirus and respiratory viruses, and serology tests (dengue, rubella and parvovirus B19) were performed. the main symptoms were rash (n=60), pruritus (n=54), and arthralgia (n=47); 51 individuals did not present fever; Zika virus was identified in 18 cases (12 in Paraíba, four in Maranhão and two in Rio Grande do Norte), and antibodies to dengue, in 14 cases. the symptoms were consistent with Zika virus fever; there was laboratory confirmation for Zika and dengue.