(WJW) — The Centers for Disease Control and Prevention announced this week that an outbreak impacting packaged salads is over.

The CDC investigated the outbreak in 2019, 2020 and it was again reopened in November 2021. In prior investigations, the agency wasn’t able to trace the source of the illness. But when the case was reopened last year, the CDC found it was packaged salads and lettuce sold by Dole that was making people sick.

In all, 18 people were sickened in 13 states. All of them were hospitalized.

Three deaths were reported – one in Michigan, one in Ohio and one in Wisconsin.

The affected people were between 50 and 94 years old.

The CDC believes the true number of people affected by the outbreak is much higher, because many people recover on their own and therefore are never tested for listeria.

Listeria symptoms can start anywhere from the same day of eating contaminated food and up to four weeks after. Symptoms include diarrhea, fever, muscle aches, nausea and vomiting.

The illnesses related to the Dole outbreak were reported over several years, ranging from Aug. 16, 2014, to Jan. 15, 2022.

Data showed that bacteria from sick people’s samples over that time period were closely related genetically. “This suggests that people in this outbreak got sick from the same food,” writes the CDC.

The discovery of the outbreak prompted a large recall of Dole packaged salads and iceberg lettuce that was processed at the company’s facilities in Bessemer City, North Carolina, and Yuma, Arizona. The recalls were issued in December 2021 and January 2022.

As of Monday, the CDC officially called the outbreak over.