Congenital Zika Virus Infection
Tracey Allen, NNP-BC
Zika virus is a single-stranded RNA virus that causes a characteristic infection in adults and can cause significant birth defects and death in fetuses. In adults, symptoms often are mild and include acute onset of fever, rash, arthralgia (joint pain), and conjunctivitis (ACOG, 2016). However, some infected individuals are asymptomatic (ACOG, 2016). Because of this, the Centers for Disease Control and Prevention (CDC) recently updated testing guidelines and now recommend laboratory testing for asymptomatic and symptomatic pregnant women who have traveled to areas affected by the Zika virus (CDC, 2016). Laboratory testing can occur 2–12 weeks after the woman returns from travel. Areas with known transmission of the Zika virus include Miami-Dade county and Miami Beach, Fl; Mexico; most of South America; and the Pacific Islands (CDC, 2016). View an updated map here.
Zika virus is transmitted most often through an infected Aedes species mosquito; however, it also can be spread from human to human via sexual transmission or blood transfusion (ACOG, 2016). This means that pregnant women whose partners have traveled to affected areas also should be considered for laboratory testing. Transmission of the virus from mother to fetus is a process that is not completely understood, but we do know that unlike other viruses, Zika virus has a unique ability to cross the placenta (LaFrance, 2016). Recent research suggests two possibilities. First, it is possible that particular cells within the placenta are favorable for this virus. These cells include Hofbauer cells, cells typically involved in keeping pathogens away from a fetus, and fibroblast cells, prolific cells that are considered the building blocks of the placenta. A second theory is that this virus is simply small enough to move through a membrane that typically only allows gas exchange and nutrient transport (LaFrance, 2016).
Zika infection can spread from mother to fetus at any time during a pregnancy; however, the most serious sequela are observed in fetuses exposed during the first and second trimesters (McCabe, 2016). Known sequela include microcephaly, ventriculomegaly, epilepsy, hydrops, impaired growth, blindness, hearing loss, psychomotor development problems, and orthopedic problems. Miscarriage and stillbirth also are associated with this virus. Microcephaly, the most clinically apparent sequela, is thought to be caused by viral destruction of neuronal progenitor cells, which leads to impaired cortical development and maturation (McCabe, 2016).
There is no vaccination to prevent Zika virus and no current antiviral therapy once a person is infected. Supportive therapy including IV hydration, antipyretics, and analgesic medications can be offered, but there is no method to prevent transmission to a fetus (CDC, 2016). For mothers who test positive for Zika virus during their pregnancy, this algorithm, published by the CDC, can be used to guide evaluation and care of the newborn.
All infants born to mothers positive for Zika virus should receive a comprehensive physical examination, cranial ultrasound, and laboratory testing for Zika virus. While awaiting laboratory results, the physical exam can guide treatment. If the physical exam is concerning for microcephaly or the cranial ultrasound is positive for ventriculomegaly or intracranial calcifications, then the infant should receive a hearing screen and an ophthalmology exam. Congenital infection is defined as the presence of Zika virus RNA or Zika virus IgM antibodies in any of the following samples obtained within the first 2 days of life: amniotic fluid, placental tissue, cord blood, newborn urine, serum, or cerebrospinal fluid (McCabe, 2016). Infants with congenital Zika virus infection should receive close developmental follow-up during the first year of life. This follow-up should include regular evaluation of the orbitofrontal cortex, a repeat hearing screen at 6 months of life because of the risk of delayed hearing loss, and evaluation of developmental milestones.
Prevention remains the only defense against Zika virus. Pregnant women and women trying to become pregnant should avoid travel to areas with known Zika transmission. For women who reside in these areas and for women who cannot avoid travel to these areas, prevention strategies should be implemented. These strategies include wearing long sleeved pants and shirts, wearing Federal Drug Administration–approved mosquito repellent, avoiding the outdoors, and keeping screens on doors and windows (CDC, 2016).
The prognosis for infants with congenital Zika virus infection is unclear. Infants with positive serologic testing combined with cerebral abnormalities will almost certainly have significant mental and physical delays. The prognosis is less certain for those with positive serologic testing but without physical findings of Zika virus (McCabe, 2016). For infants in both categories, close developmental and medical follow-up is recommended to minimize complications related to this congenital infection.
American College of Obstetricians and Gynecologists. (2016). Practice advisory on Zika Virus. Retrieved from http://www.acog.org/About-ACOG/News-Room/Practice-Advisories/Practice-Advisory-Interim-Guidance-for-Care-of-Obstetric-Patients-During-a-Zika-Virus-Outbreak
Centers for Disease Control and Prevention. (2016). Update: Interim guidelines for health care providers caring for pregnant women and women of reproductive age with possible Zika virus exposure. Retrieved from http://www.cdc.gov/mmwr/volumes/65/wr/mm6512e2.htm
LaFrance, A. (2016). The mystery of Zika’s path to the placenta. The Atlantic. Retrieved from http://www.theatlantic.com/science/archive/2016/08/the-mystery-of-zikas-path-to-the-placenta/496349/
McCabe, E. (2016). Zika virus infection: Pregnancy and congenital infection. UpToDate. Retrieved from http://www.uptodate.com/contents/zika-virus-infection-pregnancy-and-congenital-infection