Zika Virus Infection

Definition

Zika virus infection is a mosquito-borne viral disease caused by the Zika virus (ZIKV), a flavivirus transmitted primarily by *Aedes* mosquitoes. Infection is often asymptomatic or mild but can cause serious complications in pregnant women and newborns.

Epidemiology

• Endemic in tropical and subtropical regions, including Latin America, Southeast Asia, and Africa.
• Outbreaks reported globally since 2007, with major epidemics in 2015–2016 in the Americas.
• Transmitted mainly by *Aedes aegypti* and *Aedes albopictus* mosquitoes.
• Sexual transmission, blood transfusion, and vertical (mother-to-fetus) transmission documented.
• Pregnant women are at high risk for congenital infection; microcephaly and other neurological defects are most concerning.

Etiology

• Zika virus (ZIKV), a single-stranded RNA flavivirus.
• Transmission primarily via mosquito bites.
• Other routes: sexual transmission, maternal-fetal, blood transfusion, organ transplantation.
• Risk factors: living in or traveling to endemic areas, exposure to mosquitoes, sexual contact with infected individuals.

Pathophysiology

• Virus infects skin cells, dendritic cells, and then spreads via bloodstream (viremia).
• Invades various tissues, including neural progenitor cells, leading to congenital brain abnormalities.
• Host immune response (innate and adaptive) typically clears the virus in mild infections.
• In pregnant women, placental infection can disrupt fetal neural development.
• Rare neurological complications in adults include Guillain-Barré syndrome.