By monitoring Twitter and Facebook messages in the days following the Street Spice Festival, which took place from February 28 to March 2 2013, PHE inspectors were able to identify individuals exhibiting symptoms of food poisoning and connect them to the consumption of coconut chutney. The chutney was made using contaminated uncooked curry leaves from one particular stall selling Asian-style foods.
In a presentation to last week’s Advisory Committee on the Microbiological Safety of Food (ACMSF) meeting in London, Dr Kirsty Foster, a consultant in health protection with the PHE Centre North East and chair of the outbreak control team, described an investigative trail that led to the source of infection being identified as Salmonella Agona phage type (PT) 40 and other gastrointestinal pathogens associated with raw curry leaves.
The Salmonella Agona strain had not been seen in human samples or food in the UK before and that helped track it back to the curry leaves, said Foster. “In this case we were very fortunate in that there were some left over leaves from the event,” she added. The curry leaves had been imported to the UK from Pakistan and were ready bagged at the time of import.
Social media was ‘very useful’
The use of social media helped to speed the location of the source of the outbreak. Social media was “a very useful way of passing information out to people”, said Foster. “It is something that people are using more and more and we have to get more savvy about it.”
Up to 20 people began reporting symptoms of illness to officials on the Monday (March 4) following the festival, which attracted over 12,000 visitors over three days. The numbers reporting symptoms increased rapidly over the next three days as a multi-agency outbreak team was convened, said Foster. After a week to 10 days the number had increased to about 400, she added.
In total, 592 people were affected, mainly in an age range of 20 to 49 years old. But subsequent analysis estimated that a total of 926 people were probably made ill.
Tests on stool samples showed that the outbreak was caused by a mixture of pathogens, ranging from Salmonella to Campylobacter, E.coli O157, Shigella, as well as Bacillus cereus, Clostridium perfringens, Norovirus and Cryptosporidium.
On-line cohort study
While traditional incident identification routes through people’s doctors or via the local environmental health department were used, further cases were identified through an on-line cohort study, said Foster, using both Twitter and Facebook. “There was a lot of chat for those people associated with this,” she added. “The Twitter discussion was very extreme in this outbreak.”
Dr Russell Gorton, from PHE Field Epidemiology Services North East, said social media was used to approach the attendees. “There was a strong association with the guest chef items,” he said. From those approached via social media, 827 complete responses were gathered and 306 were defined as cases.
The risks of using raw curry leaves were not understood by the food operators involved in this outbreak and there was uncertainty about guidance for their use. The Food Standards Agency has since updated its advice that curry leaves should be properly cooked before they are eaten.
“We are all going to have to deal with multiple pathogen outbreaks in the future,” said ACMSF chair Professor Sarah O’Brien.
Meanwhile, the Food Manufacture Group will be staging a free-to-attend Big Video Debate entitled: Social media: Threat or opportunity for food and drink manufacturers, at the Foodex trade event at the National Exhibition Centre at 11am on Monday March 24. For more details email firstname.lastname@example.org.