Part of the problem is a lack of firm data. Researchers don’t know the rate at which the virus is spread from mosquitoes to humans or from humans back to mosquitoes, or if mosquitoes can transmit the virus to their offspring, said Alessandro Vespignani, a professor of computer science and public health at Northeastern University. Even accurate information about the number of people who have been infected in Brazil has been hard to come by.

“There are a still a lot of things which are fuzzy, so it will not be easy to get accurate modeling for what’s going on,” said Vespignani, who is trying nonetheless.