From Australia to Wisconsin to cucumbers, epidemiology is getting hammered with a bunch of people defending their turf by saying, there’s no definitive proof.
The hepatitis A outbreak in Australia linked to Chinese frozen berries that has now sickened 19 has prompted many an Aussie to proclaim, I’ll never use frozen berries, without acknowledging they live in a sub-tropical climate, not Canada. And that preservation technologies work, when used properly.
The raw milk dairy farmers in Pepin County, Wisconsin, are denying charges that their raw milk served at a potluck dinner last September sickened at least 39 students and coaches affiliated with the Durand High School football team with Campylobacter.
Information collected from 65 students, coaches and parents indicated that consumption of milk was the only exposure statistically associated with the illness, DHS spokeswoman Jennifer Miller said.
For instance, the report said that some of the 38 people sickened at the dinner did not eat chicken, that 32 drank unpasteurized milk, and that six others drank milk consumed from a store-bought jug that could have contained pasteurized or unpasteurized milk.
Also, DATCP staff collected cow manure specimens from the Reeds’ cows and genetic fingerprinting proved that the bacteria that caused the illness at the dinner was the same bacteria strain found on the Reeds’ farm, Miller said.
But it’s the Salmonella-in-cucumbers outbreak – publicly unknown until a week ago — that reveals how deep interests influence.
An 18-week Salmonella outbreak linked to fresh cucumbers in 2014 sickened at least 275 people across 29 U.S. states, and killed one man.
Several of us in the food safety world – and probably the cucumber-consuming world – were left wondering, why didn’t we know about this?
Here’s the explanation from Dr. Bob (Bob Whitaker, chief science officer at the U.S. Produce Marketing Association; if anyone calls me Dr. Doug, I glare, and say, that’s Dr. Evil to you; I didn’t spent seven years in Evil University to be Mr. Evil):
The Centers for Disease Control (CDC) issued their Morbidity and Mortality Weekly Report (MMWR) today. Anything with “morbidity” and “mortality” in the title is probably not going to rank highly on your general reading list and this weekly report was fairly typical of the reports published by CDC; highly technical and detailed, very informative, but probably targeted to a fairly specific audience.
So mere mortals are too dumb to understand?
Unfortunately, the process of identifying the cause of an illness outbreak and then further identifying how the people became ill and where that product originated from involves, as a first step, time consuming reporting of patient sample microbiology from local communities to states and perhaps up to the federal level. Often the process of just collecting this type of information and recognizing that there may be an illness outbreak exceeds the shelf life of our perishable products. Once an outbreak has been recognized, the epidemiological traceback or the process of determining what people might have come in contact with to make them ill can begin.
Epidemiology involves patient surveys, case control studies and correlation coefficients and can be time consuming and may yield multiple potential contamination vehicles. Finally, once potential food vehicles are identified, a traceback can be conducted to learn where patients might have obtained or consumed a specific food and investigators can work back to where the food was ultimately grown, harvested, packed or processed. Once production locations are identified, investigators can take microbial samples in an attempt to match any strains from the production environment to those isolated clinically from patients or in some limited cases from the food itself. Often by the time all of these vitally necessary steps have been completed, the crop is long gone and direct proof for how the contamination occurred or the source of the contamination is impossible to ascertain. Such was the case described by this Salmonella outbreak related to cucumbers.
CDC also disclosed that they employed consultations with industry experts early on in their investigation to gather information about industry practices, crop production cycles in the suspected region and product distribution. This is a positive step and is the result of a great deal of effort by the industry and CDC to determine how to engage industry to better inform investigations.
More accurate and rapid epidemiological investigations will ultimately help our industry determine what went wrong when these unfortunate illness outbreaks occur and are assigned to a produce item. This will help us direct research efforts aimed at identifying mitigation steps that can reduce the risk of further occurrences and assist operators in building improved risk and science-based food safety programs.
So why wasn’t the public informed there were a bunch of sick people?
Sounds more like the produce cone of silence.
Kirk Smith, epidemiology supervisor for the Minnesota Department of Health, told the Washington Post four years ago it’s rare for scientists investigating foodborne illness outbreaks to test the exact food suspected of carrying pathogens. By the time symptoms occur and a foodborne illness is reported and confirmed, the product in question has likely been consumed or has exceeded its shelf-life and been thrown away.
Instead, scientists, like detectives, interview victims, collect data, analyze patterns and match food “fingerprints” to determine the likely source of an outbreak.
“The majority of outbreaks, we don’t have the food to test,” Smith said. “Laboratory confirmation of the food should never be a requisite to implicating a food item as the vehicle of an outbreak.
“Epidemiology is actually a much faster and more powerful tool than is laboratory confirmation.”
As we have written, often during an outbreak of foodborne illness there are health officials who have data indicating that there is a risk, prior to the public. During the lag period between the first public health signal and some release of public information there are decision makers who are weighing evidence with the impacts of going public.
There is no indication in the literature that consumers benefit from paternalistic protection decisions to guard against information overload.