Zika virus spreads to new areas — region of the Americas, May 2015–January 2016
Published Date:January 29, 2016
Corporate Authors:National Center for Immunization and Respiratory Diseases (U.S.). Division of Viral Diseases. ; National Center for Emerging and Zoonotic Infectious Diseases (U.S.). Division of Foodborne, Waterborne, and Environmental Diseases. ;
Series:MMWR. Morbidity and mortality weekly report ; v. 62, no. 3, p. 55-58
Description:Recommendations for pregnant women considering travel to an area of Zika virus transmission -- Recommendations for pregnant women with history of travel to an area of Zika virus transmission -- How to treat pregnant women with diagnoses of Zika virus disease.
On January 22, this report was posted as an MMWR Early Release on the MMWR website (http://www.cdc.gov/mmwr).
Zika virus is a mosquito-borne flavivirus that was first identi- fied in Uganda in 1947 (1). Before 2007, only sporadic human disease cases were reported from countries in Africa and Asia. In 2007, the first documented outbreak of Zika virus disease was reported in Yap State, Federated States of Micronesia; 73% of the population aged ≥3 years is estimated to have been infected (2). Subsequent outbreaks occurred in Southeast Asia and the Western Pacific (3). In May 2015, the World Health Organization reported the first local transmission of Zika virus in the Region of the Americas (Americas), with autochthonous cases identified in Brazil (4). 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 (5). 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* (Figure) (6). Further spread to other countries in the region is being monitored closely.
Although local transmission of Zika virus has not been docu- mented in the continental United States, Zika virus infections have been reported in returning travelers (7). In light of the recent outbreaks in the Americas, the number of Zika virus disease cases among travelers visiting or returning to the United States is likely to increase. These imported cases might result in local human-to-mosquito-to-human spread of the virus in limited areas of the continental United States that have the appropriate mosquito vectors.
Zika virus is transmitted primarily by Aedes aegypti mosqui- toes (1,7). Aedes albopictus mosquitoes also might transmit the virus. Aedes aegypti and Ae. albopictus mosquitoes are found throughout much of the Americas, including parts of the United States, and also transmit dengue and chikungunya viruses. In addition to mosquito-to-human transmission, 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 (5). 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 (5).
During outbreaks, humans are the primary amplifying host for Zika virus. An estimated 80% of persons who are infected with Zika virus are asymptomatic (2). 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 (5,7,8). 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 (8). Guillain-Barré syn- drome also has been reported in patients following suspected Zika virus infection (5). 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.
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