BOGOTA (Thomson Reuters Foundation) - The mosquito-borne Zika virus, 'strongly suspected' of links to birth defects in babies in Brazil, has spread to more than 30 countries in the Americas.
The World Health Organization (WHO) declared the outbreak an international health emergency on Feb. 1.
At least 12 groups are working to develop a Zika vaccine but the WHO says licensed products could take "a few years" to reach the market.
Health authorities are trying to eliminate the places where mosquitoes lay their eggs in water, such as buckets, flower pots and tyres.
Some countries have turned to other methods to prevent the spread of Zika.
In El Salvador, the Sambo fish is being hailed as one weapon against the Aedes aegypti mosquito that carries the Zika, dengue and chikungunya viruses.
Sambo fish eat the mosquitoes' larvae in water.
Health workers and volunteers nationwide are distributing Sambo fish which are placed in water tanks and open containers used to store water in schools, restaurants and homes.
"These have been successful ... the central effort should be to mobilize the whole society against the Zika-carrying mosquito," Eduardo Espinoza, El Salvador's vice minister of health, recently wrote in a letter to the New York Times.
Pesticide spraying is being stepped up across Latin America, particularly in Brazil and Colombia that have the highest number of reported Zika cases.
Trucks are spraying city streets, shopping malls and cemeteries with pesticide fog to kill adult mosquitoes.
Health experts warn fogging may not kill mosquito larvae in hard-to-reach places such as under beds and in closets unless residents open their windows to let in the pesticide mist.
In Brazil, the government has mounted a door-to-door campaign and authorised public health officials to enter properties by force to search for breeding spots and use indoor foggers, pesticides that stick to walls.
In Piracicaba city in Brazil's Sao Paulo state, genetically modified Aedes aegypti mosquitoes have been released in mosquito-infested areas, a new weapon against Zika.
When genetically modified male mosquitoes mate with females of the same species, their offspring die at the larva stage.
This strain was developed by Oxitec, the UK subsidiary of U.S. synthetic biology company Intrexon.
Oxitec has said it released 25 million of its OX513A mosquitoes in a neighbourhood of Piracicaba between April and November and reduced the number of wild larvae of the Aedes mosquito there by 82 percent.
It has said it will start a new factory in Piracicaba to rear more genetically modified mosquitoes that will "have capacity to protect over 300,000 people."
Health authorities in Panama are also considering releasing millions of GM mosquitoes to stem the spread of the Zika virus.
"Fogging followed by the controlled release of genetically modified mosquitoes may be worth considering for halting the spread of Zika," the WHO said this week.
Reporting by Anastasia Moloney, editing by Tim Pearce. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit news.trust.org