The CDC has declared the Chipotle E. coli outbreaks over. As for its origin(s), we may never know. Yesterday the CDC provided its latest and final update regarding the two outbreaks, stating that investigators used whole genome sequencing to dig a bit deeper, and isolates tested from those sickened in the second outbreak (sickened five people in three states) were not genetically related to isolates from the people who fell ill in the initial outbreak (55 sickened in 11 states, with 21 hospitalizations).

“We are pleased to have this behind us and can place our full energies to implementing our enhanced food safety plan that will establish Chipotle as an industry leader in food safety,” said Steve Ells, founder, chairman and co-CEO of Chipotle in a company statement. “We are extremely focused on executing this program, which designs layers of redundancy and enhanced safety measures to reduce the food safety risk to a level as near to zero as is possible. By adding these programs to an already strong and proven food culture, we strongly believe that we can establish Chipotle as a leader in food safety just as we have become a leader in our quest for the very best ingredients we can find.”

While the outbreaks “appear” to be over, the fact that the source will remain a mystery is a bit unsettling. All the CDC can tell us is that the “likely” source was a common meal item or ingredient served at Chipotle Mexican Grill. Regulatory officials simply cannot trace a food or ingredient to the outbreak. “When a restaurant serves foods with several ingredients that are mixed or cooked together and then used in multiple menu items, it can be more difficult for epidemiologic studies to identity the specific ingredient that is contaminated,” according to the CDC’s final update on the outbreak.

The most recent reported illness started on December 1, 2015. No deaths were reported as a result of either of the outbreaks.

Today Chipotle released its Q4 2015 earnings, reporting a 6.8% decrease in revenue ($997.5 million) compared to Q4 2014. However, 2015 revenue increased 9.6% over 2014.

The problems are not over for the restaurant chain either. On January 28, Chipotle was served another subpoena that broadened the scope of the existing DOJ investigation. The company stated the following in a release, “The new subpoena requires us to produce documents and information related to company-wide food safety matters dating back to January 1, 2013, and supersedes the subpoena served in December 2015 that was limited to a single Chipotle restaurant in Simi Valley, California. We intend to fully cooperate in the investigation.”