The World Health Organization anticipated in January that the Zika virus may continue to spread and will likely reach all countries and territories of the region where the Aedes mosquitoes, responsible for its transmission, are found. People have not been previously exposed to the virus, so there is a lack of immunity, and this allows the virus to spread more easily. Besides, the Aedes mosquito can be found in all the Americas except Canada and continental Chile, according to the WHO. Scientists of Brazil, country where the outbreak was noticed last May, have noted a connection between higher rates of babies born with microcephaly and the spread of Zika. The number of cases of microcephaly has risen to 3,893 since authorities began investigating the surge in cases in October, according to numbers of the Brazilian Health Ministry, which is working with Brazilian and foreign laboratories to obtain a vaccine against the virus. The WHO recommends pregnant women should avoid mosquito bites and also consult doctors before planning a trip to countries where the virus circulates, and authorities should control mosquito populations by eliminating potential wet breeding grounds. According to data presented in January by the Pan American Health Organization, the Zika virus have spread to Barbados, Bolivia, Brazil, Colombia, Ecuador, El Salvador, Guadeloupe, Guatemala, Guyana, French Guyana, Haiti, Honduras, Martinique, México, Panama, Paraguay, Puerto Rico, Dominican Republic, Saint Martin, Suriname and Venezuela.