A recently completed insurance investigation reported that an outbreak of shigella at the Dartmouth Hitchcock Medical Center this fall was not deliberate.
The outbreak initially affected two laboratory technicians in September, then five more in October. The state investigators and the Center for Disease Control in Atlanta ruled out the possibility of intentional infection in the five later cases but not in the first two.
The highly contagious disease is transmitted orally and causes watery diarrhea and dehydration.
The CDC originally suspected deliberate infection because shigella bacteria are not believed to survive in the ambient air for more than one day, but the first two lab technicians showed symptoms of the disease three and seven days after transporting the specimens between freezers.
Richard Burke of the American International Group, with the support of Brown University Medical School Professor Leonard Mermel and Harvard University Medical School Professor Donald Goldman, reputed this claim, saying that shigella can survive for days on a dry surface and for months in water.
"I found no demonstrable evidence to support a claim of intentional conduct," Burke wrote in a report prepared for William Geraghty, vice president at the Mary Hitchcock Memorial Hospital.
In regard to the possibility that an individual within the hospital caused the infection, Goldman said, "No evidence has been unearthed that would lend credence to this hypothesis."
DHMC spokesperson Laurie Storey-Manseau said the report on the investigation done at the hospital "speaks for itself."
After its initial report, the CDC recommended that the DHMC enlist the assistance of the state attorney general's office to examine the cause of the first two infections.
The state investigation is not yet complete.
Burke wrote, "It is most reasonable to conclude that Shigella bacteria were transferred to doors or other surfaces, either by the gloves or the ungloved hands of the other employee, or that the contamination spread as the result of further handling of the gloves by employees who later used them."
The freezer containing the Shigella sonnei cultures malfunctioned, necessitating transfer of the bacteria, during which the contamination most likely occurred.
Burke also requested an investigation by the Federal Bureau of Investigation in hopes that it would "help dispel any concerns about DHMC's commitment to learn the cause of the outbreak," according to the report.
After reviewing the information, the FBI decided not to bring charges and postponed further decisions until the other investigations are complete.
Burke declined to comment on the investigation further than what is in his report.
