Outbreaks of gastrointestinal infections halved in the first six months of the COVID-19 pandemic in England, but bacterial pathogens fell the least, a study has found.
Compared to the 5-year average from 2015 to 2019, there was a 52% decrease in these outbreaks in the first half of 2020, from 3,208 to 1,544.
There was also a 34% drop in lab-confirmed cases, from 42,495 to 27,859.
The changes may reflect an actual reduction or be due to a change in healthcare provision, care-seeking behavior or laboratory testing practices, the study published in the journal BMJ Open found.
Public health actions to slow the spread of COVID-19, such as improving hand hygiene, played a key role, but several other factors also impacted the numbers, the researchers said. . Control measures included better hand hygiene, reduced social contact, social distancing, increased environmental cleaning and closure of premises.
They added that if this level of hygiene was maintained once the pandemic was over, there could be a permanent reduction in gastrointestinal infections. Evidence suggests that bacterial pathogens, which are more often foodborne and less influenced by hygiene and social distancing, were less affected.
The researchers used data from seven English surveillance systems coordinated by the UK Health Security Agency (UKHSA), formerly Public Health England, and Google Trend data, from January to August 2020.
Reports of norovirus fell the most while Salmonella and Cryptosporidium also fell. The proportion of lab-confirmed patients with Giardia, Shiga toxin-producing E. coli (STEC), and Listeria during the COVID outbreak period remained comparable, while reports of Campylobacter increased.
Salmonella has likely been reduced by government guidelines on non-essential overseas travel. Campylobacter was less impacted than other pathogens, although possible explanations for the initial reductions include food business closures and improved hygiene limiting the risk of cross-contamination, the researchers said.
Reports of outbreaks in food outlets also declined before the lockdown and remained low until pubs and restaurants reopened for dine-in customers.
Many factors behind the changing numbers
During the pre-COVID outbreak phase, weeks 1-4, reported gastrointestinal outbreaks were comparable to historical numbers. From week 7, called the early outbreak phase, there was a 22% decrease in outbreaks from the 5-year average of 651 to 510. This trend continued with an 87% reduction gastrointestinal outbreaks during the late lockdown phase of weeks 19-22; from a 5-year average of 350 to 46 households.
During the COVID-19 response period, there was a significant reduction in parasitic outbreaks from 32 to two and bacterial outbreaks from 97 to 51.
In terms of patients, a decrease in reports appeared from week 10, the pre-containment phase with a minimum of 2,859 cases between weeks 13 and 18 at the start of the containment phase representing a decrease of 66% on the 5-year average of 8,345.
Laboratory-confirmed cases began to increase from week 16, reflecting the historical seasonal pattern of gastrointestinal pathogen activity, despite numbers remaining significantly below average.
Data from Google Trends showed that searches for key phrases, such as “food poisoning”, “gastroenteritis” and “disease bug”, all dropped between weeks 11 and 13, while trends for “wash of hands” and “disinfection” increased significantly between weeks 8 and 14.
The researchers said there has been a shift in infection trends during the COVID-19 pandemic.
“The drivers of this change will likely be multifactorial; while changes in care-seeking behaviors, pressure on diagnostic services and verification of the surveillance system have undoubtedly played a role, there has probably been a genuine decrease in the incidence of some pathogens resulting from the control measures and restrictions implemented,” according to the research report.
(To sign up for a free subscription to Food Safety News, Click here.)