By Zaina Hamza

Reported gastrointestinal (GI) outbreaks in England were halved during the first 6 months of the COVID-19 pandemic compared with a similar period over the 5 years' prior, a retrospective ecological study found.

From February to July 2020, there was a 52% decrease in GI outbreaks -- including reports of food poisoning, hemolytic uremic syndrome, infectious bloody diarrhea -- and a 34% decrease in lab-confirmed cases compared to averages from the same stretch in 2015 to 2019, reported Nicola Love, PhD, of the University of Liverpool in England, and colleagues.

Across all surveillance indicators, reductions in GI illness activity was observed as COVID-19 cases started to peak.

"The change is likely to be multifactorial; changes to health-seeking behavior have undoubtedly played a significant role in the trends observed, and ascertainment through surveillance systems has likely been affected," the group wrote. "However, from our observations it appears that there has probably also been a true decrease in the incidence of GI infections most likely associated with control measures for the COVID-19 epidemic."

During the 6-month period -- which included the pre-lockdown period in England and continued through to lockdowns and finally eased restrictions -- there was a 62% reduction in suspected and confirmed viral outbreaks, including a 94% drop in parasitic outbreaks and a 47% drop in bacterial outbreaks.

The researchers also looked at Google search trend data in England during the pandemic, which revealed that searches for "food poisoning," "gastroenteritis," or "sickness bug" dropped during pre-lockdown and early lockdown weeks, while those for "disinfection" or "handwashing" increased during a similar time.

"This is thought-provoking, as it suggests that perhaps through continued strict hand hygiene and other protection measures, we may be able to significantly decrease the incidence of infections in the future," said Sara El Ouali, MD, of Cleveland Clinic Abu Dhabi in the United Arab Emirates, who was not involved in this study. "It remains to be seen whether these measures are sustainable and how they impact our social interactions."

For their study, Love and colleagues retrospectively examined regional and national surveillance data from Dec. 30, 2019 to Aug. 2, 2020 via seven U.K. Health Security Agencies that "coordinated lab, outbreak, and syndromic surveillance systems."

Pandemic data was divided into seven phases: phase 1 (pre-outbreak, weeks 1-4); phase 2 (early outbreak, weeks 5-9); phase 3 (pre-lockdown, weeks 10-12); phase 4 (early lockdown, weeks 13-18); phase 5 (late lockdown, weeks 19-22); phase 6 (lockdown easing, weeks 23-27); and phase 7 (further easing, weeks 28-31). These periods were compared to the same weeks from 2015 to 2019.

Overall there were 1,544 reported GI infections during the pandemic period (phases 2-7), as compared to an average of 3,208 during the 5 years capturing the same weeks prior to the pandemic.

GI outbreaks during the pre-COVID period of 2020 (phase 1) were comparable to the prior 5-year average. Then, a 22% reduction in GI outbreaks was seen during COVID's early outbreak period, which stretched to an 87% reduction in the late lockdown period.

There were 27,859 lab-confirmed cases during the 6-month pandemic period versus an average of 42,495 over same weeks during the 5 years before COVID. Reductions were observed across all age groups and by sex, though the study found geographical heterogeneity. Decreases were led by norovirus (5.6% vs 9.0%, respectively), though also included Salmonella spp (7.9% vs 9.5%) and Cryptosporidium spp (2.8% vs 3.9%).

Additionally, Love and colleagues found that general practitioner consultations, emergency care visits, and calls to the National Health Service helpline for diarrhea/vomiting and gastroenteritis were lower in 2020 versus 2019.

The authors acknowledged several limitations to their data, including an inability to differentiate between reduced GI infections and a true reduction in GI disease burden, as they were not able to assess whether only severe cases were being tested during the pandemic.