In November 2019, an outbreak of Shiga toxin-producing Escherichia coli O157:H7 was detected in South Yorkshire, England. Initial investigations established consumption of milk from a local dairy as a common exposure. A sample of pasteurised milk tested the next day failed the phosphatase test, indicating contamination of the pasteurised milk by unpasteurised (raw) milk. The dairy owner agreed to immediately cease production and initiate a recall. Inspection of the pasteuriser revealed a damaged seal on the flow divert valve. Ultimately, there were 21 confirmed cases linked to the outbreak, of which 11 (52%) were female, and 12/21 (57%) were either <15 or >65 years of age. Twelve (57%) patients were treated in hospital, and three cases developed haemolytic uraemic syndrome. Although the outbreak strain was not detected in the milk samples, it was detected in faecal samples from the cattle on the farm. Outbreaks of gastrointestinal disease caused by milk pasteurisation failures are rare in the UK. However, such outbreaks are a major public health concern as, unlike unpasteurised milk, pasteurised milk is marketed as ‘safe to drink’ and sold to a larger, and more dispersed, population. The rapid, co-ordinated multi-agency investigation initiated in response to this outbreak undoubtedly prevented further cases.

Contact with livestock and consumption of unpasteurised dairy products are associated with an increased risk of zoonotic and foodborne infection, particularly among populations with close animal contact, including pastoralists and semi-pastoralists. However, there are limited data on disease risk factors among pastoralists and other populations where livestock herding, particularly of dromedary camels, is common. This cross-sectional study used a previously validated survey instrument to identify risk factors for self-reported symptoms. Adults (n = 304) were randomly selected from households (n = 171) in the Somali Region of Ethiopia, a region characterised by chronic food insecurity, population displacement, recurrent droughts and large semi-pastoralist and pastoralist populations. Multivariable logistic regression assessed associations between self-reported symptoms and type of milk consumed, controlling for demographics and human-animal interaction. Consumption of days-old unrefrigerated raw camel milk was significantly associated with symptoms in the 30 days prior to the survey (AOR = 5.07; 95% CI 2.41–10.66), after controlling for age, refugee status, sanitation, camel ownership and source of drinking water and accounting for clustering. Consumption of days-old unrefrigerated raw ruminant milk was significantly associated with symptoms (AOR = 4.00, 95% CI 1.27–12.58). Source of drinking water and camel ownership, a proxy for camel contact, were significantly associated with the outcome in each model. There were no significant associations between self-reported symptoms and fresh or soured animal milk consumption. Research is needed to identify pathogens and major routes of transmission. Tailored communication campaigns to encourage safe food preparation should also be considered.

The aim of this study was to review microbiology results from testing >2500 raw drinking milk and dairy products made with unpasteurised milk examined in England between 2013 and 2019. Samples were collected as part of incidents of contamination, investigation of infections or as part of routine monitoring and were tested using standard methods for a range of both pathogens and hygiene indicators. Results from testing samples of raw cow's milk or cheese made from unpasteurised milk for routine monitoring purposes were overall of better microbiological quality than those collected during incident or investigations of infections. Results from routine monitoring were satisfactory for 62% of milks, 82% of cream, 100% of ice-cream, 51% of butter, 63% of kefir and 79% of cheeses, with 5% of all samples being considered potentially hazardous. Analysis of data from cheese demonstrated a significant association between increasing levels of indicator Escherichia coli with elevated levels of coagulase positive staphylococci and decreased probability of isolation of Shiga toxin-producing E. coli. These data highlight the public health risk associated with these products and provide further justification for controls applied to raw drinking milk and dairy products made with unpasteurised milk.

Raw milk cheeses are commonly consumed in France and are also a common source of foodborne outbreaks (FBOs). Both an FBO surveillance system and a laboratory-based surveillance system aim to detect Salmonella outbreaks. In early August 2018, five familial FBOs due to Salmonella spp. were reported to a regional health authority. Investigation identified common exposure to a raw goats' milk cheese, from which Salmonella spp. were also isolated, leading to an international product recall. Three weeks later, on 22 August, a national increase in Salmonella Newport ST118 was detected through laboratory surveillance. Concomitantly isolates from the earlier familial clusters were confirmed as S. Newport ST118. Interviews with a selection of the laboratory-identified cases revealed exposure to the same cheese, including exposure to batches not included in the previous recall, leading to an expansion of the recall. The outbreak affected 153 cases, including six cases in Scotland. S. Newport was detected in the cheese and in the milk of one of the producer's goats. The difference in the two alerts generated by this outbreak highlight the timeliness of the FBO system and the precision of the laboratory-based surveillance system. It is also a reminder of the risks associated with raw milk cheeses.

Coxiella burnetii, the causative agent of Q fever, is widely present in dairy products around the world. It has been isolated from unpasteurised milk and cheese and can survive for extended periods of time under typical storage conditions for these products. Although consumption of contaminated dairy products has been suggested as a potential route for transmission, it remains controversial. Given the high prevalence of C. burnetii in dairy products, we sought to examine the feasibility of transmitting the major sequence types (ST16, ST8 and ST20) of C. burnetii circulating in the United States. We delivered three strains of C. burnetii, comprising each sequence type, directly into the stomachs of immunocompetent BALB/c mice via oral gavage (OG) and assessed them for clinical symptoms, serological response and bacterial dissemination. We found that mice receiving C. burnetii by OG had notable splenomegaly only after infection with ST16. A robust immune response and persistence in the stomach and mesenteric lymph nodes were observed in mice receiving ST16 and ST20 by OG, and dissemination of C. burnetii to peripheral tissues was observed in all OG infected mice. These findings support the oral route as a mode of transmission for C. burnetii.

Campylobacteriosis is the most common notifiable disease in New Zealand. While the risk of campylobacteriosis has been found to be strongly associated with the consumption of undercooked poultry, other risk factors include rainwater-sourced drinking water, contact with animals and consumption of raw dairy products. Despite this, there has been little investigation of raw milk as a risk factor for campylobacteriosis. Recent increases in demand for untreated or ‘raw’ milk have also raised concerns that this exposure may become a more important source of disease in the future. This study describes the cases of notified campylobacteriosis from a sentinel surveillance site. Previously collected data from notified cases of raw milk-associated campylobacteriosis were examined and compared with campylobacteriosis cases who did not report raw milk consumption. Raw milk campylobacteriosis cases differed from non-raw milk cases on comparison of age and occupation demographics, with raw milk cases more likely to be younger and categorised as children or students for occupation. Raw milk cases were more likely to be associated with outbreaks than non-raw milk cases. Study-suggested motivations for raw milk consumption (health reasons, natural product, produced on farm, inexpensive or to support locals) were not strongly supported by cases. More information about the raw milk consumption habits of New Zealanders would be helpful to better understand the risks of this disease, especially with respect to increased disease risk observed in younger people. Further discussion with raw milk consumers around their motivations may also be useful to find common ground between public health concerns and consumer preferences as efforts continue to manage this ongoing public health issue.

In December 2016, Public Health England investigated an outbreak of campylobacteriosis in North West England, with 69 cases in total. Epidemiological, microbiological and environmental investigations associated the illness with the consumption of unpasteurised cows' milk from Farm X, where milk was predominantly sold from a vending machine. Campylobacter was detected in milk samples which, when sequenced, were identical in sequence type as pathogens isolated from cases (Clonal Complex ST-403, Sequence Type 7432). The farm was served with a Hygiene Emergency Prohibition Order to prevent further cases. To our knowledge, this is the first outbreak of campylobacter associated with unpasteurised milk in England since 1996. Our findings highlighted several important lessons, including that the current testing regime in England for unpasteurised milk is not fit for purpose and that the required warning label should include additional wording, underscoring the risk to vulnerable groups. There has been a substantial increase in both the volume of unpasteurised milk consumed in England and the use of vending machines to sell unpasteurised milk over the last 10 years, making unpasteurised milk more readily accessible to a wider population. The evidence generated from outbreaks like this is therefore critical and should be used to influence policy development.

There is world-wide increasing interest in the consumption of unprocessed, natural food commodities including fresh (unpasteurised) milk and milk products. Consumers are actively seeking out raw milk, partly due to health reasons, but also for taste, freshness, closeness to the producer and to support local agriculture. The need for high levels of hygiene and safety in farms producing raw milk for direct consumption has long been recognised and has led to federal and industry-initiated systems for safe raw milk production. Raw milk producers in North America and Europe have demonstrated that raw milk, intended for direct consumption, can be produced safe and hygienic. The aim of this paper is to describe practices that have been developed for safe raw milk production. The German Vorzugsmilch is a federally regulated programme for legal raw milk production that was established already in the 1930s to provide raw milk with high hygienic standards controlled for zoonotic diseases to consumers. The Raw Milk Institute is a non-profit organisation established in California that has developed a voluntary safe raw milk programme in North America. RAWMI has developed a risk analysis and management system for raw milk dairy farmers to assist farmers in making individually tailored solutions for various production systems. In British Colombia, Canada, small herd share farms have employed good manufacturing practices, a risk management approach and performed monthly samples for pathogens and indicator bacteria to demonstrate safety and consistency. The major components of the raw milk systems applied, and the results of regular milk microbial indicator bacteria are presented. For the German system, the results from standard monthly pathogen tests are compared to zoonotic pathogen tests from other milk sources. The overall results indicate that raw milk can be produced with a high level of hygiene and safety in various systems.

Systematic, national surveillance of outbreaks of intestinal infectious disease has been undertaken by Public Health England (PHE) since 1992. Between 1992 and 2002, there were 19 outbreaks linked to raw drinking milk (RDM) or products made using raw milk, involving 229 people; 36 of these were hospitalised. There followed an eleven-year period (2003–2013) where no outbreaks linked to RDM were reported. However, since 2014 seven outbreaks of Escherichia coli O157:H7 (n = 3) or Campylobacter jejuni (n = 4) caused by contaminated RDM were investigated and reported. Between 2014 and 2017, there were 114 cases, five reported hospitalisations and one death. The data presented within this review indicated that the risk of RDM has increased since 2014. Despite the labelling requirements and recommendations that children should not consume RDM, almost a third of outbreak cases were children. In addition, there has been an increase in consumer popularity and in registered RDM producers in the UK. The Food Standards Agency (FSA) continue to provide advice on RDM to consumers and have recently made additional recommendations to enhance existing controls around registration and hygiene of RDM producers.