Although Zika infections are usually mild and deaths are rare, health authorities are concerned because of a link between the disease and a sharp increase in birth defects in Brazil. The World Health Organization declared Monday that the Zika outbreak is a “public health emergency of international concern.”

Four out of five people with Zika have no symptoms. Those who do become ill typically have mild symptoms: fever, rash, headache, joint pain and pink eye, according to the WHO. Although more than 30 Americans have been diagnosed with Zika, these have largely been travel-related cases, which pose a relatively low risk for spreading. The continental USA is not considered to have a Zika outbreak because the virus has not become entrenched in the mosquitoes that cause the illness. FULL REPORT