mystery illness and what we need to know. it is on fox news.com right now. >> the centers for disease control is doing a terrific job going case-by-case trying to figure out what's causing this. >> sandra: 90% of these cases are affecting children younger than 18 years old. >> that's why we worry, because otherwise they're healthy. >> sandra: if you want to know more about this illness and how it's spreading go to our website. >> bill: the migrant caravan making its way through mexico. utah senator mike lee has big ideas how to deal with it before it arrives. he is our guest live next. >> security standpoint there is no proper accounting of who these individuals in the caravan are. and this poses an unacceptable security risk to the united states.