French health officials have published a report on a 2019 E. coli outbreak linked to raw milk cheese.

It was the third outbreak linked to raw milk cheese in the country in the past year, according to Santé publique France. It is also being considered a hemolytic uremic syndrome (HUS) outbreak. HUS is a type of kidney often associated with E. coli infections.

The E. coli outbreak prompted public health authorities to reinforce messages on the risk associated with consumption of unpasteurized, raw milk products by young children.

In a week in April 2019, seven cases of pediatric HUS were reported to Santé publique France, compared to fewer than 10 per month in April, historically.

The Shiga-toxin-producing E. coli (STEC) O26 outbreak was from March to mid-May. In total, 19 cases were identified, with 18 /confirm/ied, of which 17 had HUS and were hospitalized. One child and an adult only had diarrhea. Of HUS cases, eight had neurological complications.

The oldest patient was aged 63 but all the others were younger than 5 years old. The youngest was 6 months old. The fact that almost all cases were in the under 5 age group suggests a low level of contamination, more likely to affect young children, according to Santé publique France.

Patients lived in eight regions of France and 53 percent were female. For 18 cases, a strain of STEC O26 with the stx2 and eae genes was isolated.

Origin of contamination not found
Consumption of Saint-Félicien and/or Saint-Marcellin cheese was reported for 15 of the 18 patients confirmed either by them or their family circle. Traceback identified La Fromagerie Alpine, based in the Drôme region of France, as the common producer.

For seven cases, the buying of incriminated cheeses was listed on loyalty cards. For the others, the cheeses were sold in the place of purchase cited by families during interviews.

Investigations at the cheese factory and with milk suppliers failed to identify the origin of contamination. All food and environmental samples from the producer were negative. This included sampling from 167 cheeses and milk from 10 vats. Cheeses were distributed to 33 countries, but no additional cases were reported.

In late April, the complete production of La Fromagerie Alpine was recalled because of initial results of epidemiological, microbiological and traceback investigations. The production of raw milk cheese was suspended and the milk was sent for pasteurization. From mid-May, the company was allowed to restart marketing of thermized milk cheeses, which uses a lower temperature for a shorter period of time than pasteurization. Normal cheese production was authorized to resume at the end of August.

Authorities checked milk producers to verify compliance with good hygiene practices and analyzed milk filters from about 30 producers supplying the company. E. coli was found twice but it was not related to the outbreak strain.

Earlier this year, Santé publique France published a report on another STEC O26 outbreak in March to May 2018 linked to raw milk reblochon produced by Chabert. It involved 14 patients younger than the age of 5 with 13 developing HUS and one death.

Highest HUS levels recorded
Meanwhile, 168 cases of pediatric HUS were reported to Santé publique France in 2019 which is the highest number recorded since surveillance started in 1996 and up from 154 in 2018 and 164 in 2017.

The incidence is highest in children younger than 3 years old, and decreases with age.  A summer increase is seen every year, according to officials. Duration of hospital stay is available for 45 patients and ranged from one to 30 days.

The high incidence in 2019 is partly explained by the outbreak of STEC O26 in connection with consumption of raw milk cheese.

Regional incidence shows a significant disparity each year. This past year, the highest rates were in Corsica, Auvergne-Rhône-Alpes and Occitanie. The latter two regions were particularly affected by the O26 outbreak.

As in 2018, the most frequent serogroup was O26, with a total of 62 cases in 2019, followed by O80 in 21 cases and O157 10 times.