The Zika Virus: One of the world's most frightening viruses has reached the U.S. Dr. Jon LaPook speaks with the country's top scientists about the fight against Zika.The Battle for Mosul: After more than two years of ISIS occupation, Iraq's second-largest city is being taken back by the Iraqi Army. Lara Logan reports from Mosul.The National Mood: In two days, American voters will send a president to the White House, but both the leading candidates have the highest disapproval ratings in U.S. history.