Gastrointestinal infection outbreaks halved during the first six months of the COVID-19 pandemic in England but bacterial pathogens declined the least, according to a study.
Compared with the 5-year average from 2015 to 2019, there was a 52 percent decrease in such outbreaks in the first half of 2020 from 3,208 to 1,544.
There was also a 34 percent decline in laboratory confirmed cases from 42,495 to 27,859.
Changes may reflect a real reduction or be because of altered healthcare provision, health-seeking behavior or laboratory testing practices, found the study published in the journal BMJ Open.
Public health actions to slow the spread of COVID-19, such as improved hand hygiene, had a key role but several other factors also impacted the figures, said researchers. Control measures included better hand hygiene, reduced social contact, social distancing, increased environmental cleaning, and closure of premises.
They added if this level of hygiene was maintained once the pandemic is over, there could be a permanent reduction of gastrointestinal infections. Evidence suggests bacterial pathogens, which are more commonly foodborne and less influenced by hygiene and social distancing, were less impacted.
Researchers used data from seven English surveillance systems coordinated by the UK Health Security Agency (UKHSA), previously Public Health England, and Google Trend data, from January to August 2020.
Norovirus reports fell the most while Salmonella and Cryptosporidium also declined. The proportion of lab-confirmed patients with Giardia, Shiga toxin-producing E. coli (STEC) and Listeria during the COVID outbreak period remained comparable, while Campylobacter reports increased.
Salmonella was likely reduced by government guidance on non-essential foreign travel. Campylobacter was less impacted than other pathogens, although possible explanations for initial reductions include food business closures and improved hygiene limiting the risk of cross-contamination, according to the researchers.
Reports of outbreaks in food outlets also reduced prior to lockdown and remained low until pubs and restaurants reopened for dine-in customers.
Many factors behind shifting figures
During the COVID pre-outbreak phase, from weeks 1 to 4, reported gastrointestinal outbreaks were comparable to historic figures. Beginning with week 7, called the early outbreak phase, there was a 22 percent decrease in outbreaks from the 5-year average of 651 to 510. This trend continued to an 87 percent reduction in gastrointestinal outbreaks during the late lockdown phase of weeks 19 to 22; from a 5-year average of 350 to 46 outbreaks.
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, decreased reports were apparent from week 10, the pre-lockdown phase with a low of 2,859 cases between weeks 13 and 18 in the early lockdown phase representing a 66 percent decrease on the 5-year average of 8,345.
Lab-confirmed cases began to rise from week 16 onward, mirroring the historic seasonal trend for gastrointestinal pathogen activity, despite numbers remaining significantly lower than average.
Google Trends data showed searches for key phrases, such as “food poisoning” “gastroenteritis” and “sickness bug” all dropped between weeks 11 and 13, while trends for “handwashing” and “disinfection” rose substantially between weeks 8 and 14.
Researchers said there had been a shift in trends of infections during the COVID-19 pandemic.
“The drivers of this change are likely to be multifactorial; while changes in health seeking behavior, pressure on diagnostic services and surveillance system ascertainment have undoubtedly played a role, there has likely been a true decrease in the incidence for some pathogens resulting from the control measures and restrictions implemented,” according to the research report.
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