It was probably the kitchen sink: 82 sick with Salmonella from UK restaurant 2015-16

From Eurosurveillance:

It is estimated that over 38,000 community cases of salmonellosis occur annually within the United Kingdom (UK) [1,2]. Salmonellosis often results from consumption of contaminated food or water [3], however, transmission via asymptomatic shedding by food handlers and exposure to contaminated environments where conditions are favourable for pathogen survival have also been implicated [3,4]. Here we report the findings of an investigation of an outbreak of salmonellosis where the environment was pivotal in continued transmission.

On 7 March 2015, Public Health England (PHE) East Midlands was alerted by the clinical microbiology laboratory of a local hospital to 21 cases of Salmonella enterica serovar Typhimurium gastroenteritis, with onset in February 2015. Seven cases in this initial phase of the outbreak required hospitalisation. Following this notification we suspected there was a community outbreak of S. Typhimurium; investigations and attempts to control the outbreak followed.

Hypothesis-generating interviews at the outset of the investigation identified that several cases had eaten at the same restaurant during the incubation period for their illness. Descriptive epidemiological analyses including subsequent cases pointed to the restaurant being the likely source. This popular, purpose (newly) built restaurant had opened only 18 months before the outbreak. The restaurant offered a full table-service menu, self-service salad bar and hot self-service carvery buffet serving roasted meats (turkey, beef, gammon and pork at weekends) and vegetables and condiments. Despite interventions to control the initial outbreak, cases continued to emerge followed by a prolonged period of transmission until 2016. The evolution of the investigation into this community outbreak and subsequent control measures is described, with specific reference to the use of whole genome sequencing (WGS) to link isolates and the role of the drains in continued pathogen transmission.

Mapping and visual inspection of the drainage systems identified significant issues. Water filled traps (u-bends) designed to prevent foul air flow from the drainage system into the building had failed and smoke testing revealed some ineffective drain seals, potentially allowing contaminated bio-aerosol to be disseminated into the kitchen. One sink drain was not connected to any drainage system with waste water pooling under the floor. Other larger drains had failed after leaking waste-water washed away the supporting substrate forming a cavity under the kitchen area. It transpired at that point that drainage water had, on occasion, risen into the kitchen area, although this had not been previously reported. Substantial remedial works were undertaken, however, these were found to have failed on re-inspection and so these drains were later decommissioned.

Biofilm [15] and flooded areas in underfloor cavities may have sustained this outbreak, after repeated environmental cleaning failed. Drainage problems in one area of the kitchen led to liquid from the drains seeping into the kitchen suggesting a contamination pathway. We found isolates matching the outbreak strain on kitchen cloths, swabs from kitchen sinks, and pot wash areas suggesting contact with sinks may have provided a second contamination pathway. We also identified ineffective drain water-traps potentially allowing the movement of contaminated bio-aerosols [13]. Smoke tests demonstrated the potential for dissemination of foul air into the kitchen.

Investigation using whole genome sequencing of a prolonged restaurant outbreak of salmonella typhimurium linked to the building drainage system, England, February 2015 to March 2016

Eurosurveillance, John Mair-JenkinsRoberta Borges-StewartCaroline HarbourJudith Cox-RogersTim Dallman, Philip AshtonRobert JohnstonDeborah ModhaPhilip MonkRichard Puleston,


The vomit machine, not just for parties; useful for modeling norovirus

I’ve been lucky to be close to some excellent projects, some of the stuff and knowledge created through these projects ends up mattering to food safety nerds – especially those who are making risk management decisions. NC State student Grace Tung-Thompson’s PhD project on vomit spray and norovirus is one of the most impactful. The work was carried out as part of the USDA NIFA-funded NoroCORE project led by my friend Lee-Ann Jaykus.VOMIT-BLOG-HEADER-698x393

I’ve talked to lots of Environmental Health Specialists, retailers and food service food safety folks about what Grace and fellow graduate student Dominic Libera put together and many respond with a weird level of enthusiasm for the barf project.

Mainly because a real question they struggle with is how far will virus particles travel from an up-chuck event – knowing this, and then cleaning and sanitizing helps limit the scope of a potential outbreak. Today Grace’s work was published in PLOS ONE.

Matt Shipman, Research Communications Lead for University Communications and all around great guy writes about the project for The Abstract:

Tucked away in a quiet lab on NC State’s Raleigh campus is something that looks like a glorified air compressor with a grotesque clay face. It’s called “the vomiting machine” and it does exactly what you think it does. Researchers are using it to study one of the most widespread pathogens in the United States: norovirus.

Norovirus is a group of more than 30 related viruses that can cause vomiting and diarrhea. Norovirus affects about 20 million people each year in the U.S., with infections that can lead to hospitalization and occasionally to death, particularly in the elderly. About a quarter of the time, “noro” infection is obtained by consuming contaminated foods or water.  However, it is most often spread between people in close contact with each other.  The epidemic GII.4 strain predominates, but there are others.

But how, exactly, is noro transmitted from person to person?

“Epidemiological studies have suggested that norovirus can be ‘aerosolized’ through vomiting, meaning that small particles containing norovirus can become airborne when someone throws up,” says Grace Thompson, a recent Ph.D. graduate whose work at NC State focused on how norovirus spreads through vomiting and how long it is detectable in vomit. (Fun fact: noro can still be detected in dried vomit after six weeks.)

“According to outbreak reports, it appears that people can become infected with noro if they are directly or indirectly exposed to vomiting events,” Thompson explains. “If aerosolized particles land on a countertop, you could also touch the counter with your hand, then touch your hand to your mouth, leading to infection.”

But while norovirus aerosolization by vomiting has long been suspected, no one knew if it was actually occurring. This is the sort of question that Lee-Ann Jaykus’s lab lives for.

Jaykus is a professor of food science at NC State and scientific director of the U.S. Department of Agriculture-National Institute of Food and Agriculture Food Virology Collaborative, also known as NoroCORE (short for Norovirus Collaborative for Outreach, Research, and Education). They are, quite simply, norovirus experts.

To see if vomiting could really aerosolize norovirus, researchers in Jaykus’s lab (including Grace Thompson) needed a controlled way to observe and study vomiting over and over again. They needed a vomiting machine.

As you may imagine, there is a limited demand for vomiting machines, so the researchers had to design and build their own. They found a partner in Dominic Libera, a graduate student in NC State’s civil, construction and environmental engineering department in Francis de los Reyes’s lab.  They also needed data upon which to build their model.  Dr. Kenneth Koch, a gastroenterologist with Wake Forest University, provided that expertise.

Working together, the researchers created a machine that is essentially a scaled-down version of the mouth, esophagus, and stomach – made of tubes and a pressure chamber that passes through a clay face to give it the correct vomiting angle. The machine is designed (using engineering similitude principles) to let researchers control the pressure and volume of the vomit, in order to mimic a range of natural vomiting behaviors. The whole thing is enclosed in a sealed plexiglas box and placed under a biosafety hood. (A short video of the machine can be seen here.)

Instead of vomit, the researchers use liquid solutions of different viscosities or thicknesses as “artificial vomitus” to reflect different stages of digestion. And, since they cannot use real norovirus, they used a bacteriophage called MS2, which is a virus that infects E. coli but is harmless to humans. MS2 is easy to culture and is a common stand-in for noro.

Putting The Machine To Work

In 2012 and 2013, the team did extensive testing of the machine, to make sure that it was scaled appropriately and worked the way they wanted it to. And in 2014, Thompson began using the machine for formal experiments.

And what did they find? Well, virus was indeed aerosolized.  Although the amount of MS2 aerosolized as a percent of total virus “vomited” was relatively low (less than 0.3 percent), vomit from infected people contains millions of particles. When the math is done, this means that the actual amount of virus particles aerosolized during a single vomiting event ranges from only a few into the thousands, perhaps more. (This work was recently published in PLOS ONE. More information on the findings is available here.)

“And that is enough to be problematic because it only takes a few, perhaps less than 20, to make a susceptible person ill” Jaykus says. “This machine may seem odd, but it’s helping us understand a disease that affects millions of people. This is work that can help us prevent or contain the spread of norovirus – and there’s nothing odd about that.”