The World Health Organization regards Zika as an international emergency.BY ANGELA CHARLTON The Associated Press PARIS – Drugmaker Sanofi Pasteur said Tuesday it is launching an effort to research and develop a vaccine to prevent the Zika virus, after the World Health Organization declared a global emergency over its explosive spread across the Americas. There is no treatment or vaccine for the mosquito-borne virus, which has been linked to birth defects and is in the same family of viruses as dengue. Sanofi made the first dengue vaccine shot, licensed last year in Brazil after years of scientific struggle to develop one. Sanofi’s Dr. Nicholas Jackson, who is leading the company’s Zika effort, said it will leverage experience with the dengue vaccine, yellow fever and Japanese encephalitis. It hopes existing manufacturing capabilities, technology and ongoing studies in 10 countries on the dengue virus will also help speed up the search. Vaccine development typically takes years. Jackson, head of global research for Sanofi Pasteur, said the company wants to “greatly accelerate” the hunt for a vaccine. “It’s very difficult to predict a reliable timeline … given that we’re learning so much about the disease and what we need to do,” he told reporters. U.S. government announced last week that it is beginning research into a possible vaccine. Dr. Anthony Fauci of the National Institutes of Health said there are vaccines in various stages of development for other viruses in the same family — dengue, West Nile and chikungunya. The Zika virus was long thought to be relatively benign, with generally milder symptoms than dengue. But amid a large recent Zika outbreak in Brazil, researchers began reporting an increase in a rare birth defect named microcephaly, in which babies are born with abnormally small heads. Clinical trials for the Zika vaccine, however, would be particularly difficult as they might involve testing in women of child-bearing age and pregnant women, groups that scientists have traditionally been loathe to put at risk.