Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN) Pregnant women should not travel to Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde and Samoa because of Zika virus, the CDC said Friday. This comes on the heels of last week's travel alert from the CDC recommending pregnant women postpone travel to Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela and Puerto Rico. The recommendations also call for women who have traveled to these places during their pregnancy be screened and monitored for the virus if their visit took place while the virus was present in the country they visited.CDC expands list of nations pregnant women should avoidEl Salvador, Jamaica and Colombia tell women not to get pregnantCDC says Zika virus has been transmitted by blood transfusion, in the lab and sexually 
 Question:The decision is based on their ongoing monitoring of the Zika virus around the world and _ say they will update as necessary in the interest of public health.

CDC