Every click on a building to collect materials or Simoleons, or simply interacting with a building, can trigger an outbreak. As soon as a building is contaminated, a maximum of three ambulances will be dispatched from the Hospital. If there is more than one Hospital in the city, the vehicles will come from different locations, regardless of their proximity to the outbreak.
The player may click on an infected building before any ambulances reach it and this will increase the speed at which the vehicles arrive at the cost of one energy. If ambulances have already arrived and are attending to the outbreak, clicking on the building will have no effect.
It is possible for more than one outbreak to happen at the same time. If there is only one Hospital in the city, three vehicles will be dispatched to the first outbreak and will return to the Hospital before attending the second outbreak. Clicking on the second outbreak while the ambulances are still at the first will have no effect.
There are three different types of outbreak. Minor emergency, emergency and major emergency. The more severe the outbreak, the harder it is to cure. If an outbreak is successfully cured after the player has clicked on the building to call the vehicles faster, a cash reward will be given. This is 200 for a minor emergency, 500 for an emergency and 1000 for a major emergency. There is also a small chance of receiving a Medal of Bravery, X-ray or Police Badge.