The Zika virus is getting a lot of media attention so the Centers for Disease Control has issued an update. The American Council on Science and Health is posting it as a public service
Zika is a mosquito-borne flavivirus first identified in 1947 in Ugunda but until 2007, there were only sporadic human disease cases in Africa and Asia. In May 2015, the World Health Organization reported the first local transmission of Zika virus in Brazil. In December, the Ministry of Health estimated that 440,000 1,300,000 suspected cases of Zika virus disease had occurred in Brazil in 2015. By January 20, 2016, locally-transmitted cases had been reported to the Pan American Health Organization from Puerto Rico and 19 other countries or territories in the Americas.
An estimated 80% of persons who are infected with Zika virus are asymptomatic. Symptomatic disease generally is mild and characterized by acute onset of fever, maculopapular rash, arthralgia, or nonpurulent conjunctivitis. Symptoms usually last from several days to 1 week. Based on information from previous outbreaks, severe disease requiring hospitalization is uncommon, and fatalities are rare. During the current outbreak in Brazil, Zika virus RNA has been identified in tissues from several infants with microcephaly and from fetal losses in women who were infected during pregnancy.
Local transmission of Zika virus has not been documented in the continental United States, just in returning travelers, because the Zika virus is transmitted primarily by Aedes aegypti mosquitoes, which also transmit dengue and chikungunya viruses. Zika virus infections have been documented through intrauterine transmission resulting in congenital infection, intrapartum transmission from a viremic mother to her newborn, sexual transmission, blood transfusion, and laboratory exposure. There is a theoretical concern that transmission could occur through organ or tissue transplantation, and although Zika virus RNA has been detected in breast milk, transmission through breastfeeding has not been documented.
The Brazil Ministry of Health has reported a marked increase in the number of infants born with microcephaly in 2015, although it is not known how many of these cases are associated with Zika virus infection. Guillain-Barré syndrome also has been reported in patients following suspected Zika virus infection. Studies are under way to evaluate the risks for Zika virus transmission during pregnancy, the spectrum of outcomes associated with congenital infection, and the possible association between Zika virus infection and Guillain-Barré syndrome.
No specific antiviral treatment is available for Zika virus disease and no vaccine to prevent Zika virus infection is available. The best way to prevent Zika virus infection is to avoid mosquito bites by using air conditioning or window and door screens when indoors, wearing long sleeves and pants, using permethrin, a common synthetic insecticide.
Until more is known, and out of an abundance of caution, pregnant women should consider postponing travel to any area where Zika virus transmission is ongoing.