Step 7: Decide an Outbreak is Over

illustration representing the decline of cases in an outbreak by using a column chart.

An outbreak is over when the number of new illnesses drops back to what investigators normally expect. With continued public health surveillance, if the number of illnesses rises again, the investigation continues or restarts.

When is an outbreak over?

An outbreak ends when the number of new reported illnesses drops back to the number normally expected. The epidemic curve helps investigators see that illnesses are declining. Even when illnesses from the outbreak appear to have stopped, public health officials continue surveillance for a few weeks to be sure cases don’t start to increase again.

What if the number of new illnesses increases?

  • It could be that the source was not completely controlled
  • A second contamination involving another food or location is linked to the first outbreak
  • The investigation continues or restarts