Description

• Zika virus is a single-stranded RNA flavivirus discovered in 1947 in the Zika forest in Uganda.
• It is transmitted via mosquitoes (including Aedes aegypti and Aedes albopictus), sexual intercourse with an infected person (symptomatic or asymptomatic), vertical exposure (mother-to-child transmission), and blood transfusions.
• The incubation period is 3 to 10 days.
• In adults and in most children outside the neonatal period, Zika virus infection causes an acute, self-limited viral syndrome (acute Zika infection).

Epidemiology

• An epidemic of Zika virus infections and an associated congenital Zika syndrome (CZS), with central nervous system, musculoskeletal, and eye anomalies was noted in the Americas beginning in Brazil in 2015, with >50 countries affected by early 2017.
• As of December 6, 2017, the CDC reported:
  • A total of 226 locally acquired Zika virus cases (in Florida and Texas), 5,324 travel-associated cases in the United States, and 37,087 cases in U.S. territories
  • A total of 2,311 pregnant women in the United States and 4,621 pregnant women within U.S. territories with laboratory evidence of Zika virus infection
  • A total of 98 liveborn infants with birth defects and nine pregnancy losses with birth defects within the United States
• The incidence of birth defects of pregnant women in the U.S. Zika Pregnancy Registry (January to September, 2016) was 58.8 per 1,000 live births, compared to 2.86 per 1,000 live births in a “pre-Zika” cohort (2013 to 2014).

Risk Factors

• Travel to a Zika-endemic region
• Sexual intercourse with a person who has travelled to a Zika-endemic region
• In utero exposure via a mother infected with the Zika virus

General Prevention

• Prevention of primary acquisition via mosquito bites (i.e., use of insect repellent containing N,N-diethyl-meta-toluamide [DEET] in adults and in children >2 months of age, air conditioning in warm weather climates, mosquito nets in endemic areas)
• Barrier contraceptive methods or abstinence to prevent sexual transmission to pregnant women or women wishing to conceive
• Avoidance of travel to Zika-endemic regions by pregnant women, women wishing to conceive, and their male sexual partners
• No current vaccine for Zika is available.

Pathophysiology

• Mosquitoes ingest the virus after feeding on a human or animal host and transmit the virus to humans.
• In humans, Zika virus has been shown to disrupt the placental barrier and target neural progenitor cells and immature neurons, leading to abnormal fetal brain development.
• Fetal demise and congenital anomalies occur as a result of intrauterine Zika virus infection.

Commonly Associated Conditions

Zika virus infection has been associated with Guillain-Barré syndrome during epidemics in French Polynesia and Brazil.