Countries dealing with Zika outbreaks should consider using controversial methods to fight its spread, such as using genetically modified mosquitoes and biological agents that stop mosquito larva from hatching, the World Health Organization said Tuesday.
"Given the magnitude of the Zika crisis, WHO encourages affected countries and their partners to boost the use of both old and new approaches to mosquito control as the most immediate line of defense,'' the agency said.
The WHO said its advisory board recommended trials using "sterile irradiated male mosquitoes," a technique used to fight dengue in the Cayman Islands. It says other U.N. agencies have deployed sterilized mosquitoes to control other agricultural pests.
But environmentalists have cautioned against the use of genetically modified mosquitoes, saying the long-term effects of killing off an entire insect population is unknown.
The Zika virus is transmitted primarily by the Aedes aegyoti mosquito.
Also Tuesday, the U.S. Food and Drug Administration recommended people who have had potential exposure to Zika put off donating blood for at least four weeks.
They include people who show any symptoms of Zika, anyone who has traveled to a Zika-stricken area, and those who have had sex with someone who lived in or traveled to one of those countries in the last three months.
"The FDA has critical responsibilities in outbreak situations and has been working rapidly to take important steps to respond to the emerging Zika virus outbreak," acting chief scientist Luciana Borio said Tuesday. "We are using this guidance for immediate implementation in order to better protect the U.S. blood supply."
While there are no cases of Zika virus entering the U.S. blood supply, the FDA says the latest scientific evidence shows the risk of blood transmission is likely.
There is currently no treatment for Zika, and much remains unknown about the disease.
Experts suspect Zika could cause microcephaly, a condition in which babies are born with unusually small heads because the brain has not developed properly or has stopped growing.
The Zika virus is becoming a major problem in Latin America, particularly in Brazil, which reports more than 4,300 suspected cases of microcephaly.
