By Jan Worth-Nelson
An outbreak of shigella bacteria in Genesee and Saginaw counties over the past eight months does not appear to have been caused by Flint’s drinking water system, a team of researchers from the Centers for Disease Control and Prevention told the Flint Recovery Group by phone in a presentation at City Hall Thursday.
A total of 180 cases of the highly-contagious disease, called shigellosis, which can cause severe abdominal discomfort and bloody diarrhea, have been confirmed since March — 129 in Genesee County and 51 in Saginaw County, according to Jevon McFadden, a medical epidemiologist with CDC’s Career Epidemiology Field Officer Program,
The disease primarily struck children locally — with 51 percent of those afflicted 9 years old or younger. A total of 26 percent were younger than 5.
McFadden said the outbreak had peaked in June and July and has subsided dramatically since, with no new cases reported since Oct. 31.
The CDC team came to Flint in early October to work with the state Department of Health and Human Services and the Genesee County Health Department to investigate the outbreak. They have been interviewing members of households where people got sick, collecting and testing bacteria samples and mapping where illnesses have occurred “to see if there is a link between water quality issues, like water main breaks and low chlorine levels and the people who got sick,” McFadden said.
He said the interview portion of the work is finished, and that results still are coming in on the lab testing and mapping.
However, Paul McClung, an epidemic intelligence service officer with the CDC’s Waterborne Disease Prevention Branch, offered three “initial conclusions” from the work completed so far.
First, shigella does not appear to be spreading through a drinking water system — a concern vital to Flint residents uneasy about the dangers of the system in light of the water crisis.
The researchers reported that “almost all of the people from Flint who got sick (90 percent) drank only bottled water.” In fact, 65 percent of Flint residents who contracted the disease drank only bottled water to brush their teeth.
“Because so few of these people were consuming water from the drinking water system, it is likely they became infected with Shigella bacteria from a source other than the water,” the researchers stated.
Also,” the people who got sick did not share a common drinking water source, suggesting water use is not likely to be a common link between people who got sick. They used water from multiple different drinking water systems, and more than 15 percent used water from private wells.
Second, shigella bacteria appear to be spreading in the community from person to person — particularly the young. A total of 59 percent of those who got sick either wore diapers, changed diapers, or came into contact with a person wearing diapers in the week before they became ill.
“This suggests the bacteria could have been passed from the feces (poop) of sick children to their siblings, friends or caregivers — one of the most common ways Chigella bacteria spread in a community.”
The researchers said their data suggests the outbreak did not seem to originate from a single source, such as a restaurant, drinking water system, or swimming pool.
Third, the outbreak is slowing down, with no new cases reported so far in November.
Nonetheless the researchers strongly urged continuing prevention efforts, in particular “good hand washing.” A handout provided at the meeting emphasized frequent hand washing with soap and water after using the toilet or changing diapers, before preparing food or eating, and after blowing your nose, coughing or sneezing.
The conclusions presented to the FRG Thursday also were summarized in a memo signed by Dr. Michael Beach from the CDC, along with Dr. Eden Wells from the Michigan Department of Health and Human Services and Dr. Gary Johnson from the Genesee County Health Department.
In a follow-up email, McFadden added that the CDC’s Career Epidemiology Field Officer Program “assigns experienced CDC epidemiologists to field sites in response to requests from state and local health departments,” and is one of the forms of assistance that CDC provides. The focus of field assignees like McFadden and his team, he said, is on “building epidemiologic capacity within state and local health departments for responding to a variety of public health emergencies, including outbreaks like the shigellosis one in Saginaw and Genesee Counties.”
EVM Editor Jan Worth-Nelson can be reached at firstname.lastname@example.org.