Zika Virus Screening

Infection

Zika virus, discovered in 1947 and named after the Zika forest in Uganda, is a primarily Aedes aegypti mosquito–borne ribonucleic acid (RNA) flavivirus. The first human Zika infection occurred in 1952. The first epidemic outside of Africa and Asia occurred in 2007 in the Yap Islands. A Zika epidemic occurred in Brazil in 2015–16. In February 2016, the World Health Organization declared the suspected link between Zika virus disease and microcephaly—a Public Health Emergency of International Concern. Data from the French Polynesian Zika outbreak that occurred in 2013–14 strongly supported the hypothesis that Zika infection in the first trimester of pregnancy was associated with an increased risk of microcephaly. Furthermore, 3% of samples from asymptomatic blood donors contained detectable Zika virus RNA during the outbreak, which caused concern for transmission by blood transfusions.

In 2017, data from the US Zika Pregnancy Registry reported that the rate of Zika virus–associated birth defects was 11%–15% if the infection occurred within the first trimester. Laboratory evidence of possible Zika virus infection included a positive Zika virus RNA NAT or detection of recent Zika virus infection or recent unspecified flavivirus infection by serologic tests, i.e., positive or equivocal Zika virus IgM and Zika virus plaque reduction neutralization test (PRNT) titer ≥10 and Dengue virus PRNT <10. Zika disease is nationally reportable.

Although pregnant women were asymptomatic in 62% infected, birth defects were reported in similar proportions whether or not the mother acknowledged symptoms of Zika virus disease. Birth defects associated with Zika are defined by the Registry as microcephaly, calcium deposits in the brain indicating possible brain damage, excess fluid in the brain cavities and surrounding the brain, absent or poorly formed brain structures, abnormal eye development, confirmed hearing loss, and other problems from damage to the brain that affects nerves, muscles, and bones, such as club foot or inflexible joints. The most recent update on data from 2017 stated that there were 2191 completed pregnancies, i.e., live births, miscarriages, stillbirths, and terminations, with or without Zika-associated birth defects. Of those, 106 live-born infants and 9 pregnancy losses had Zika-associated birth defects, which constitute ∼5% of the completed pregnancies.

Zika virus infections are asymptomatic in about 80% of individuals. Mild symptoms may consist of fever, rash, headache, myalgia, conjunctivitis, and arthralgias. Guillain–Barre may occur.

Determination of Need and Requirement for Testing

The FDA issued final guidance recommending either NAT or pathogen reduction of blood products.