also i'm not sure if this is possible but i had a release of unknown chemicals and the way the chemicals travel half the map was infected before i could even get a cop to respond because when people get sick they just keep going with there lives you should make them collapse or something. Since the teams have realistic response time it's just impossible
The same happens in that event in EM4 Deluxe, people get infected but it takes rather a long time for them to collapse so sometimes they have left the map (in Deluxe that is)