The mosquito-borne Zika virus has spread quickly in the past two years through the Pacific Islands and South America. Although there have been no reported deaths from the illness, a spate of recent outbreaks is cause for concern.
Earlier this fall, after Colombia reported its first cases of Zika virus infection, the World Health Organization recommended countries in North and South America step up efforts to identify and track the virus. Last week, cases were reported in the Yucatan in Mexico and in the Caribbean. And doctors in Brazil are trying to determine whether the virus may be linked to a spike in the number of babies with a congenital brain deformity called microcephaly.
Here's what we know about Zika.
What is it? Zika virus infection can cause Zika fever — an illness often accompanied by rash, fever, joint pain and conjunctivitis. It is spread by mosquitoes of the Aedes genus, including A. aegypti, the same mosquito species that carries the dengue and chikungunya viruses. Severe illness happens less often with Zika infections than with dengue infections, but "while Zika virus infections have been recognized for some time, large outbreaks have only been recognized within the last decade and we are still trying to understand the full spectrum of illness," says Susan Hills of the Center for Disease Control's Division of Vector-Borne Diseases.
Where is it? After it was first described in 1952, Zika virus sporadically infected people in Africa and parts of South and Southeast Asia. Just 14 cases were reported in about 50 years. Then, in 2005, Zika virus was spotted for the first time outside Africa and Asia on Yap, an island in the western Pacific Ocean. The virus subsequently spread to other island nations in the Pacific, and eventually landed in the Americas on Easter Island in Chile in early 2014. Brazil reported Zika virus infections in May 2015, and since then, health authorities there have found the virus in 14 different states. In October, Colombia reported its first cases, and last week, the virus was reported in Yucatan, Mexico, and in the Caribbean. No cases have been reported in the United States, and although there are Aedes mosquitoes in parts of the country, the likelihood of a future outbreak is low.
How is it spread? Zika virus is primarily spread by several different species of Aedes mosquitoes. There have been reports of Zika virus being spread perinatally, from mother to infant either during birth or soon afterward. Authorities also worry that it might be spread via blood transfusions. The virus can be spread sexually, too, though only one case of sexual transmission has been documented. Mosquitoes, however, are by far the major avenue of spread and the focus of prevention strategies.
What are the symptoms? Only 1 in 5 people infected with Zika virus experience symptoms. Those who do get ill usually report fever, rash, joint pain and conjunctivitis, and sometimes headaches, muscle pain and vomiting. The illness lasts about a week. Cases severe enough to require hospitalization are rare and no deaths have been reported, but the virus has been linked to some alarming complications. During a French Polynesian outbreak in 2013, a few people developed Guillain-Barre syndrome after Zika virus infection, and Brazilian authorities are investigating whether the virus causes microcephaly in fetuses of infected pregnant women. Babies with the defect are born with underdeveloped brains. Health authorities are still investigating Zika's role in both conditions.
Treatment and cure? There is no treatment for Zika virus infection. Painkillers and fever reducers help manage the symptoms until the infection clears, usually in about a week.
How do we stop it? Prevent mosquitoes from breeding in standing water near dwellings, promote the use of window screens and bed nets, and encourage people to wear long sleeves and pants.
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