Zika, a relatively new virus, is the subject of worldwide concern because of its rapid spread and its apparent connection to a neurological birth disorder.
Here are 10 things to know about Zika right now:
It is spread by mosquitoes. It is not passed through incidental human contact.
Symptoms in adults tend to be mild, such as body aches, rashes, fever, headaches and inflamed eyes, lasting about a week. An estimated 80 percent of people infected with Zika show no symptoms.
Since November, Zika has been linked to nearly 4,000 cases of microcephaly in Brazil – a birth defect where babies are born with abnormally small craniums and limited brain development. It also has been linked to Guillain-Barre Syndrome, a neurological disorder that causes paralysis.
Brazilian health officials made the connection after finding many of the mothers had experienced Zika-like symptoms in the early stage of their pregnancies. Brazilian authorities recommend women in affected areas avoid getting pregnant until the disease abates.
U.S. health authorities advise pregnant women to avoid traveling to 23 countries where Zika is currently active. Pregnant women who have recently traveled to those countries should be monitored for Zika symptoms.
Zika was first discovered in Uganda in 1947. The first documented outbreak occurred in Micronesia in 2007. Subsequent outbreaks occurred in southeast Asia and the western Pacific. The current outbreak in the Americas began in Brazil last May. By Jan. 20, locally transmitted cases had occurred in more than 20 countries, including Puerto Rico.
About 20 cases of returning travelers with the disease have been reported in the United States. They include a Hawaiian baby born with microcephaly after his mother returned from Brazil.
The World Health Organization warns Zika is likely to spread to all countries in the Americas except for Canada and Chile. Aedes mosquitoes, the main vector for Zika transmission, occur in all but those countries. It is the same mosquito that carries Dengue fever and yellow fever.
With no vaccines or anti-viral medications available, the best protection against Zika at this time is to avoid being bitten by mosquitoes.
It is not clear why the virus appeared in Brazil and why it is now causing microcephaly. Some speculate that travelers attending 2014 World Cup soccer matches may have transmitted the disease. Some question whether the virus has evolved.
Sources: Centers for Disease Control and Prevention reports, Reuters and CNN news reports, interviews with Asit K. Pattnaik of the Nebraska Center for Virology at the University of Nebraska-Lincoln and Daniel Brooks, senior research fellow with the H.W. Manter Laboratory of Parasitology at UNL