Linda Bock at the Worcester Telegram & Gazette News yesterday (Jan. 9) wrote what might end up being the definitive wrap up piece on the Whittier Farms listeriosis outbreak.
With three elderly dead and one pregnant woman suffering a miscarriage, Bock reports that health officials cannot say the outbreak is over. That’s because listeria has an incubation period of 70 days. Milk processing was shut down by state health officials on Dec. 27, meaning the incubation period will run to March 6.
Bock also reports the current outbreak is the third listeriosis outbreak involving pasteurized milk in the country. She says:
The first documented outbreak of listeriosis in pasteurized milk in the country occurred between June 30, 1983, and Aug. 30, 1983, when 49 people in Massachusetts contracted listeriosis, according to a report in the New England Journal of Medicine on Feb. 18, 1985. According to the journal, seven of the cases occurred in fetuses or infants and 42 in immuno-suppressed adults; 14 patients died. Testing at the time revealed that the illness was strongly associated with drinking a specific brand of pasteurized whole or 2 percent milk. The milk associated with the disease came from a group of farms where listeriosis in dairy cows was known to have occurred at the time of the outbreak.
In a CDC weekly report published Dec. 16, 1988, the 1983 Massachusetts outbreak implicated pasteurized whole milk or 2 percent milk. However, an inspection of a milk-producing plant detected no apparent breach in the pasteurization process, prompting further interest in the effectiveness of pasteurization.
Since then, several studies have shown that listeria bacteria are killed by pasteurization, according to the CDC. After reviewing the studies, a World Health Organization working group on food-borne listeriosis concluded in 1988 that “pasteurization is a safe process which reduces the number of Listeria monocytogenes (bacteria) occurring in raw milk to levels that do not pose an appreciable risk to human health.”
The second documented listeriosis outbreak involving pasteurized milk occurred in the Midwest in 1994. After an outbreak of gastroenteritis and fever among people who attended a picnic in Illinois, health officials determined that 45 people associated with the consumption of chocolate milk got sick with diarrhea and fever. Four people were hospitalized.
The Whittier Farms dairy is in Shrewsbury, Massachusetts, about 35 miles west of Boston.
For Bock’s complete story, go here. It’s a good read.