From time to time, I am asked why food safety hazards seem more prevalent now than they were two, three or more decades ago.

Why are more types of food at risk?

Where were Norovirus, Listeria monocytogenes, and other foodborne pathogens back then?

Why were we able to sample raw cake batter and raw cookie dough when we were kids without our parents worrying about Salmonella?

Much has changed in food production, processing and distribution in the last fifty years.

When I was growing up in the 50s and 60s, most food to be found in grocery stores was still sourced locally. Produce was seasonal; we never saw fresh blueberries and strawberries in the our local grocery store in mid-winter.

The coming of large-scale food production and distribution was the harbinger of significant change to the way produce was harvested and the way food animals were raised.

Back then, large cattle feedlots for ‘finishing’ beef were the exception rather than the rule. My mother bought her meat and poultry from a neighborhood butcher shop and her bread from a local bakery. In short, if a food was contaminated, the extent of the potential outbreak was limited to the local market reach.

Amassing cattle in large feedlots under crowded conditions enhanced the potential spread of infections, resulting in the need to introduce antibiotics into the feed. At the low levels used, these antibiotics promoted ‘growth’ (ie., cattle fattened more quickly); however, they also promoted the development of antibiotic-resistant strains of bacteria.

The accumulated excrement from the cattle contaminated groundwater in the vicinity of the feedlots, increasing the spread of bacteria such as Salmonella and E. coli into the environment, including the wild animal populations.

Where fields were being farmed in the vicinity of feedlots, there was an increased potential for irrigation water or run-off from rain to spread the bacteria to the growing crops.

In the 50s and 60s, there was no effective method to detect norovirus. Illnesses that today are attributed to norovirus infections were written off as “stomach flu” instead.

Some of the bacterial pathogens common today, notably, shiga-toxin producing E. coli, including E. coli O157:H7, are relatively recent mutations. The earliest report in the literature of an E. coli O157:H7 outbreak dates from 1983.

Large-scale production requires large-scale distribution networks, including transportation of liquid ingredients in tanker trucks. A Salmonella outbreak resulted from the transportation of pasteurized ice cream mix in a tanker that had previously carried liquid raw egg, and that hadn’t been sanitized between uses.

Climate change also has played a role. For example, shellfish are known to harbor Vibrio parahaemolyticus. However, this pathogen is cold-sensitive and was not a food safety hazard in the waters off the coast off Canada’s west coast in the past. With the rise in water temperatures, Vibrio parahaemolyticus has been found more frequently in shellfish harvested in those waters.

In 2007, ASM Press published my book, “Food Safety: Old Habits, New Perspectives.” Although now more than 11 years old, much of its content is still current.

As technology changes, so must the old habits we grew up with. By relying on yesterday’s food preparation methods, we lay ourselves open to tomorrow’s health threats.