Zika virus is a flavivirus that is transmitted by the Aedes aegypti mosquito. It was first detected in humans in 1952 in Uganda as mild sporadic illnesses. The first recorded outbreak occurred in 2007 in Micronesia [1]. This was followed by other outbreaks including one in French Polynesia in 2013 that first described Zika-associated cases of Guillain-Barré syndrome and microcephaly [2]. Between 2015 and 2016 another outbreak in Brazil reported increased incidence of fetal demise and microcephaly and other anomalies in infants exposed to Zika in utero [3]. This was identified as a new strain of Zika that spread rapidly through many areas of the Americas, with similar reports of increased incidence of congenital Zika syndrome (CZS) including neurologic, ocular, and neurodevelopmental abnormalities. Birth defects ranged from 7% to 46% in these outbreaks [4]. With these original reports, an international public health emergency was declared by the World Health Organization (WHO). According to WHO, as of July 2019, 87 countries have had reported Zika infections including in the United States (WHO Zika Epidemiology Update).

Globally, however, it is estimated that 61 countries and territories have the vector for Zika but with no reported cases. In the United States this includes large urban and rural areas including California, Texas, Florida, Louisiana, and most southern and midwestern states. It is inevitable that there will continue to be waves of outbreaks with new cases of CZS and other neurologic diseases. The Centers for Disease Control and Prevention has been extensively involved in investigating new US cases of Zika and has come up with case definitions and guidelines for the care of pregnant women and their newborns. However, it is imperative to better understand the full spectrum of disease among Zika-exposed infants as they get older so that the international community can prepare for the long-term care of these infants, as well as to focus on preventive measures and vaccine development. In the current issue of Clinical Infectious Diseases, Adachi and colleagues describe 1-year outcomes of 156 infants exposed to Zika in the Brazil outbreak. Zika infection was confirmed using polymerase chain reaction (PCR) either in the mother (N= 145) or the infant at birth (N= 11). Among the 156 infants, 98 (or 62.8%) were asymptomatic, 36 had CZS, and 22 were otherwise symptomatic. Infants had extensive evaluations using standardized methods by appropriate specialists to evaluate growth and development, hearing, vision, and neurologic outcomes. Infants were categorized as (1) small for gestational age (SGA; N= 14),(2) having proportional microcephaly (PM; N= 13),(3) having disproportional