By: Christopher Hsu, MD, PhD, MPH, FAAP
Zika virus disease (Zika) is a viral infection primarily spread by Aedes aegypti and Aedes albopictus species mosquitoes, the same types of mosquitoes that spread dengue and chikungunya viruses. First discovered in the Zika forest of Uganda in 1947, outbreaks were reported in Africa, Southeast Asia, and the Pacific Islands before the first reported case in Brazil in May 2015. In the following months, Zika spread throughout Central and South America, the Caribbean, and Oceania/Pacific Islands. Symptoms of Zika are usually mild and include fever, rash, joint pain, and red eyes, but many people with Zika won’t get sick. Because the symptoms of Zika are so similar to those of dengue and chikungunya, clinical diagnosis of Zika can be a challenge for clinicians. Once a person recovers from Zika, they are likely immune from future infections. What has alarmed clinicians and the public are the increased reports of birth defects in babies born to women infected with Zika during pregnancy, and a rare neurologic condition known as Guillain-Barré syndrome (GBS) in areas affected by Zika. Because of the alarming geographic spread of Zika, and its link to birth defects and GBS, the Centers for Disease Control and Prevention (CDC) activated its Emergency Operations Center to level 1, the highest level, in February 2016.
Since that time, much has been learned about Zika. The clinical and scientific evidence has shown that Zika infection during pregnancy is a cause of microcephaly and other fetal brain defects. Microcephaly can result in permanent developmental and long-term health complications in infants, so pregnant women are considered most at risk for severe effects from Zika. Furthermore, there is evidence that the virus can be spread through the semen of infected men. Thus, men who have visited areas with Zika could spread the virus to sexual partners in countries without Zika.
Unfortunately, there is currently no vaccine to prevent Zika, and there is no treatment, except supportive treatment of symptoms. The best way to prevent Zika is to prevent mosquito bites: wear insect repellent and clothing that covers most of the skin, stay in places with air conditioning and window and door screens, and sleep under a bed net if air conditioning or screened rooms aren’t available. It is also recommended that pregnant women not travel to areas with Zika, and if a partner has been in an area with Zika, use condoms during sex and avoid having sex during pregnancy. People who think they might have Zika should talk to their doctor.
What is still not known is if there is a time during pregnancy when the fetus is at highest risk of birth defects or if a pregnant woman’s symptoms are associated with an increased risk of birth defects for the fetus. Although Zika has not been spread by mosquitoes in the continental United States, cases have been reported in US territories and among travelers coming to the continental United States from areas with Zika. The CDC cannot predict how much the virus would spread in the United States if mosquitoes were to become infected here, but many areas of the United States have the types of mosquitoes that can spread the virus. For more information about Zika virus, see CDC’s Zika website.
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