In medicine, it's known as a “never” event — something that's never supposed to occur in a health care facility.

But in six cases in other states over the past two decades, patients were infected with hepatitis C because a health care worker who had the virus passed it on, according to Dr. Joseph Perz, an epidemiologist for the national Centers for Disease Control and Prevention in Atlanta, Ga.

And five of those outbreaks involved employees who were stealing narcotics, he said.

Investigators now believe an employee at Exeter Hospital who was injecting drugs meant for patients was the likely source of an outbreak that to date has infected 19 patients — and one hospital employee — with the chronic liver disease.

“We have a high level of confidence, based on what we know and what we have seen happen in other states, that drug diversion is the only real explanation here,” Dr. Jose Montero, the state's public health director, said Friday.

Montero said there is nothing that prohibits someone with hepatitis C from working in a health care facility. “If all the policies and systems are in place, it doesn't matter,” he said.

But the male employee who has the same strain of the virus as the 19 infected patients was suspended “as soon as the investigation began, in mid-May,” according to Ryan Lawrence, a spokesman for Exeter Hospital.

Montero refused to say — or rule out — whether that individual is a target of the criminal investigation by the New Hampshire Attorney General's Office into the outbreak.

But Montero promised a full accounting of what went wrong at Exeter Hospital. “Something failed dramatically here, and at some point when we are done with the investigation, we are going to disclose all of the details,” he said.

“Yes, one crafty person may have been doing this, but it shows a failure in the system of care,” he said.

As of Friday, the state has received 776 blood samples for testing; 683 have shown no evidence of infection, Montero said. There were 26 positive tests, 20 that match the strain of the virus linked to Exeter Hospital's cardiac catheterization lab and six unrelated cases.

Montero said the state also has asked all the clinicians in the region to look for any cases of hepatitis C diagnosed over the past year. “It's labor intensive,” he said. “We are still going through those records.”

Colorado, Florida

In similar recent outbreaks in Colorado and Florida, hepatitis C cases were traced to hospital employees who were abusing the painkiller fentanyl. In each case, the employee injected the drug from pre-filled syringes that had been prepared for medical procedures.

The employee then replaced them with contaminated syringes filled with saline, which was administered to patients instead of the painkillers they needed.

In both states, the employees involved were prosecuted by federal authorities, charged with tampering with a consumer product and with theft of narcotics.

The U.S. Attorney's Office in Concord could not be reached for comment last week.

Jane Young, associate attorney general, would not say whether the U.S. Attorney's Office is also involved in the Exeter case. But she said, “We are marshaling all resources, including state, local and federal resources.”

Once the investigation here is complete, Young said, if authorities determine there is criminal liability, they will decide whether state, federal or local authorities will prosecute.

Montero said the Centers for Disease Control and Prevention has been advising the state Health Department as it looks for the cause and extent of the outbreak, the first such incident in New Hampshire. The CDC is also doing some additional genetic testing of positive samples, he said.

No HIV found

Early on in the investigation, Montero said, his division did some testing for other diseases, including HIV, the virus that causes AIDS. “And we didn't find anything, so we are not testing everybody,” he said.

A team from the Health Department's Bureau of Licensing and Certification is also about to make a second visit to Exeter Hospital at the request of federal regulators, according to John Martin, manager of that agency. Investigators typically look at the hospital's policies and procedures for “how medications are dispensed, how medications are disposed of and so on, just to see: Are there appropriate safeguards in place?” Martin said.

Montero said complacency is often why the systems designed to prevent such incidents fail. “We are so certain sometimes that we have everything in place that we stop looking,” he said.

He said he plans to bring the results of his investigation to the state's health care quality commission. “We expect that there are going to be a lot of painfully learned lessons here,” he said.

The CDC's Perz says drug diversion by health care workers “is an under-recognized problem.” One survey found that 4 percent of hospital workers admitted illicit drug use.

An “increasing risk''

Perz, who co-authored a recently published study of a Hepatitis C outbreak discovered at Florida's Mayo Clinic in 2010, warns that infection spread by health care workers is “a real and perhaps increasing risk.”

“And my hope is that the silver lining for incidents like the ones in Texas, Colorado, Florida and perhaps New Hampshire will lead to better patient protections,” he said.

To restore public trust, Perz said, “I think that the health care community broadly needs to indicate that it is aware of these hazards and is doing everything in its means to eliminate such risk.”

“Even if the risk is small ... the harm can be catastrophic,” he said.

John Clayton, vice president for communications at the New Hampshire Hospital Association, said previous hepatitis C outbreaks in other states “triggered monumental introspection among health care providers.”

And the same will happen here, Clayton said. “Certainly, every hospital in New Hampshire will go back and re-examine its practices and make certain that this tragedy that's taking place at Exeter Hospital will not be repeated,” he said.

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Shawne Wickham may be reached at swickham@unionleader.com.