Editor’s Note: This piece has been updated with comments from HCR ManorCare attorneys.

A 2013 hepatitis C outbreak at a North Dakota nursing home that made headlines as one of the largest outbreaks in U.S. history was likely due to “infection control lapses,” researchers reported last week.

In a study published online in the American Journal of Infection Control, investigators with the Centers for Disease Control and Prevention found through epidemiologic and molecular data analysis that the virus was likely spread patient to patient in “facility A” — the ManorCare Health Services-Minot in Minot, ND, where more than 40 residents were infected.

In an analysis researchers compared the Minot facility to a control nursing home, with both groups of residents receiving care at “hospital X.” They found the control to have a low prevalence of hepatitis C infections, indicating the transmission to residents did not occur at the hospital.

The analysis would appear to lift some of the blame off of the company behind “hospital X,” which was run by Trinity Health, and instead on practices inside the facility. Although the CDC team’s research was unable to pinpoint an exact mode of transmission of the virus, evidence indicates that the outbreak may have been the result of lapses in infection control within the skilled nursing facility.

“Facilities should ensure adequate infection control procedures are followed during any and all care provided to patients within the facility,” the study’s authors wrote. “Improvements in infection control at facility A successfully stopped the outbreak, highlighting the need for further strengthening infection control practices in long-term care facilities.”

Trinity Health and victims of the outbreak recently agreed in principle to a settlement in the case. 

Attorneys for HCR ManorCare contested the study’s findings in letters sent to both the North Dakota Office of Attorney General and the American Journal of Infection Control earlier this month. The letters call the CDC’s study “flawed and misleading,” and state that it may interfere with ongoing litigation in the outbreak case.

The attorneys also identify “potential weaknesses” of the study, including omitting almost half of the known victims of the outbreak, the fact that several of the victims “lack any connection to ManorCare,” and a belief that two of the victims were not exposed to the culpable phlebotomist known as “Employee A” even though data shows otherwise.

“Publishing this paper would fortify the untrue narrative, which Trinity has repeatedly disseminated for self-interested reasons, that the cause of the Minot outbreak remain unknown,” the letter reads. “The paper would continue to focus attention on an examination of ManorCare, when the facts have long shown that the roots of the outbreak lie elsewhere.”

Publication of the paper that is “arguably consistent with Trinity’s reasoning” could also put additional outbreak victims at risk by depriving them of hepatitis C testing, the attorneys note.

“As a result, the outbreak could continue to expand to additional victims, who may not learn about their infections for many years.”