here's linzie janis. >> reporter: tonight, a drastic new recommendation for expecting couples. the cdc saying men returning from zika-affected countries should use protection with their partner for the entire pregnancy, or abstain altogether. but mosquitoes are still the primary way zika is spread. lizzie morales, a houston mother, got zika over the holidays while visiting el salvador. >> you have no strength, no energy, to do anything. not to even sit down. >> reporter: her symptoms subsided. but three deaths in colombia now blamed on zika. biologist matthew degennaro showing us a potential tool to fight the virus -- genetically modified mosquitoes. >> when you release the males, they go breed with females just of this species and render them sterile. >> reporter: so that knocks down the population? >> yes. >> reporter: david, in miami, they're spraying where there are to get rid of mosquitoes. >> dr. richard besser is just back from brazil. i want to get to the recommendation from the cdc, leading to the question, do we know how long the virus stays in your system? >> once yo
