Scottish health officials have admitted the surveillance of foodborne outbreaks suffered due to the pressures of the COVID-19 pandemic.
In a report on gastrointestinal and zoonotic pathogens for 2020 and 2021, only outbreaks involving Public Health Scotland (PHS) are covered. Officials said as surveillance had lapsed, it was not a comprehensive record of incidents but for 2023 to 2024, ObSurv, the surveillance system for outbreaks of infectious intestinal disease in Scotland, will be re-established.
It is the first such report published by Public Health Scotland since it was established in April 2020 during the COVID-19 pandemic.
In 2020 and 2021, there were 12 outbreaks of Salmonella identified by whole genome sequencing. In 10 of them, the mode of transmission was foodborne and they were part of UK-wide outbreaks. Two outbreaks were local and were also believed to have been caused by food.
The largest was a Salmonella Enteritidis outbreak linked to processed poultry, which sickened 26 people. Salmonella Typhimurium in Brazil nuts affected 11 and Salmonella Infantis in pork scratchings caused 21 illnesses.
Nine outbreaks of Shiga toxin-producing E. coli (STEC) were reported in 2020 and 2021. Three in 2020 were caused by E. coli O157 and one by E. coli O145. In all four outbreaks, which affected 13 people, the source was linked to food and they were part of UK-wide outbreaks. In 2021, there were five outbreaks with 14 cases. Three were due to E. coli O157 and one each by E. coli O145 and E. coli O26.
In 2021, two Listeria outbreaks were recorded, which were part of UK-wide events and only one person in Scotland was sick in each incident.
Campylobacter and E. coli data
Officials said routine reporting was suspended during the early pandemic years because of “significant” service disruption, as almost all resources were redirected but a return to an annual report is planned.
In 2020, PHS received 5,392 laboratory reports of Campylobacter and this figure was 5,890 in 2021. These are down on the 5,977 reports in 2019.
The incidence rate in males remained greater than in females in 2020 and 2021, as seen in previous years. The highest rates continued to be seen in young children aged less than one year old to 4 years old and adults aged 65 and older. In 2020, the spring-summer peak was delayed, potentially because of the initial lockdown of public health measures to control the COVID-19 pandemic.
PHS received 113 lab reports of E. coli O157 in 2020 and 137 in 2021 compared to 149 in 2019. The highest incidence rates continue to be in young children aged less than one year to 4 years old and most isolates were reported in the summer months.
In 2020, there were 100 lab reports of non-O157 STEC, and 122 in 2021 versus 109 in 2019. The highest incidence rates were in young children aged less than one to 4 years old and adults aged 65 and older.
Listeria, Salmonella and Shigella figures
Thirteen cases of Listeria were recorded in 2020 and 17 in 2021. Only seven reports were noted in 2019. Most are in the 65 and over age group.
PHS received 342 reports of Salmonella in 2020 and 330 in 2021 compared to 757 in 2019. The highest incidence rates were amongst young children and elderly adults.
The two most common types remain Salmonella Enteritidis and Salmonella Typhimurium. In 2020, they accounted for 57 percent of all reports of Salmonella, and 42 percent in 2021. Other common types included Newport, Infantis, Stanley, and Agona.
There were 38 cases of Shigella in 2020 and 27 in 2021. These are down from 102 in 2019. The drop was driven by fewer Shigella Sonnei reports.
Viruses and parasites
In 2020, PHS received 211 lab reports of norovirus and 349 reports in 2021, compared to 885 in 2019. Usual seasonal trends were not seen in 2020 and 2021. The incidence rate in females was greater than in males in 2020 and 2021 and the highest rates continue to be in young children aged less than one to 4 years old and adults older than 65.
“The decrease in laboratory reports in 2020 and 2021 probably reflects the changes in social mixing, increased hygiene measures in place as well as social distancing and more stringent care and visiting arrangements in place during the COVID-19 pandemic,” according to the report.
In 2020, PHS received four lab reports of Cyclospora and one in 2021, compared to 16 in 2019. None of the four cases in 2020 were travel related but the case in 2021 was believed to have been acquired overseas.
Of 16 lab reports in 2019, 13 were thought to have become sick abroad. The drop in 2020 and 2021 may reflect changes in travel behavior related to the pandemic, according to the report.
There were 11 reports of hepatitis A in 2021 and 10 in 2020. Fifty cases were recorded in 2019.
In 2020, PHS received 127 lab reports of Hepatitis E, and 96 in 2021, compared to 158 in 2019. Fourteen cases of Yersiniosis, four of Taeniasis, and 42 of Toxoplasmosis were also recorded in 2021.
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