Zika, a virus spreading throughout South and Central America and transmitted by mosquitoes, could be headed north. The virus causes birth defects, in particular abnormally small heads on infants, and neurological problems such as Guillan-Barre syndrome. Women are being advised to avoid pregnancy as birth defects are very likely in those parts of the world. As the earth's temperature rises due to climate change, it is believed that Zika will become more widespread as the mosquitoes that carry it thrive in warmer environments. For now the CDC seems content with offering travel advisories and doesn't seem to be actively searching for a treatment or a vaccine.