CHICAGO -- Chicago officials say they're constantly evaluating security before the city's annual marathon, but no changes have been made following the deadly shooting in Las Vegas.
About 45,000 runners are expected in Sunday's marathon and there'll be 1 million spectators.
Mayor Rahm Emanuel said Tuesday that emergency officials have conducted roughly a dozen drills in the past year.
Emanuel says he has "absolute confidence" in the security plans. He says Chicago is prepared for "any eventuality" and stepped up security following the 2013 Boston Marathon bombing.
His son is running in the event.
Alicia Tate-Nadeau leads the city's Office of Emergency Management and Communications. She says emergency officials take major national and international events into account, but there haven't been any marathon security changes yet because of the Las Vegas shooting.