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I. DEFINITION

Congenital Zika syndrome (CZS) is a constellation of central nervous system (CNS), ocular, and neuromuscular abnormalities seen in newborns after in utero exposure to Zika virus, a member of the Flaviviridae virus family (which includes dengue, yellow fever, and West Nile viruses).

II. INCIDENCE

As of late August 2017, the Pan American Health Organization reported 48 countries in the Americas with vector-borne transmission of Zika virus and 27 countries and territories in the Americas with confirmed cases of CZS. As of mid-April 2018, the Centers for Disease Control and Prevention (CDC) identified 2328 completed pregnancies in the United States (including the District of Columbia) in women with laboratory evidence of possible Zika virus infection. Of these pregnancies, 115 liveborn neonates and 9 pregnancy losses had documented birth defects. The prevalence of CZS-associated birth defects in infants of women in the US Zika Pregnancy Registry during the first 9 months of 2016 was 58.8 cases per 1000 live births, roughly 20-fold greater than a “pre-Zika” cohort in 2013 to 2014.

III. PATHOPHYSIOLOGY

Zika virus is an arbovirus (arthropod-borne virus) first identified in the Zika Forest of Uganda in 1947. Mosquitoes of the Aedes genus (specifically, Aedes aegypti and Aedes albopictus) are the primary arthropod vectors and are endemic to regions of the continental United States and Hawaii, Puerto Rico, and the US Virgin Islands. In urban and suburban areas, the virus is transmitted from human to human via mosquito bites (“blood meals”) commonly during daylight hours. Sexual transmission of the virus can occur from an infected person to his or her partner and is of great concern to pregnant women or women attempting to conceive.

Human disease secondary to Zika virus had been noted sporadically worldwide until outbreaks in the State of Yap, Federated States of Micronesia in 2007 and multiple Pacific Islands from 2013 to 2016. In most cases, persons infected with Zika virus are asymptomatic. In symptomatic patients, acute Zika syndrome typically is a mild illness presenting in adults and children roughly 7 to 10 days after exposure with a pruritic, maculopapular rash, a low-grade fever, musculoskeletal discomfort (myalgia/arthritis/arthralgia), extremity edema, conjunctivitis, and headache. Zika infection and Guillain-Barré syndrome, an autoimmune-mediated peripheral neuropathy, first were associated during an outbreak in French Polynesia in 2013 to 2014; a strong link between the virus and the disease was confirmed in a later case-control study in that area.

The first outbreak of Zika infection in the Americas occurred in early 2015 in the Bahia state of Brazil, with an estimated 1.3 million cases throughout the country. Later that year, health officials in Brazil noted an increased incidence of anomalies in babies born in Zika-affected areas. Zika RNA and proteins subsequently were found in fetal and maternal tissues from microcephalic fetuses, infants, and early pregnancy losses of Brazilian mothers with symptoms of acute Zika ...

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