Back to Story
FILE - Two baby three-toed sloths and the teddy bear which functions as their surrogate mother are cared for at a wildlife center in Alajuela, Costa Rica, Tuesday, April 20, 2004, during preparations to help the animals for release. (AP Photo/Kent Gilbert, File)

FILE - Two baby three-toed sloths and the teddy bear which functions as their surrogate mother are cared for at a wildlife center in Alajuela, Costa Rica, Tuesday, April 20, 2004, during preparations to help the animals for release. (AP Photo/Kent Gilbert, File)

This 2014 photo provided by the U.S. Centers for Disease Control and Prevention shows a female Culex quinquefasciatus mosquito on the skin of a human host. (James Gathany/CDC via AP)

This 2014 photo provided by the U.S. Centers for Disease Control and Prevention shows a female Culex quinquefasciatus mosquito on the skin of a human host. (James Gathany/CDC via AP)