Laboratory reporting of norovirus in England was impacted more than Campylobacter by the COVID-19 pandemic, according to a study.

Researchers investigated the link between lab reporting of the two pathogens, the number of coronavirus tests and infection prevention and control measures during the pandemic.

In England, laboratory reports of norovirus and Campylobacter are recorded via a national surveillance system but only Campylobacter is a reportable disease. Campylobacteriosis is usually tied to eating undercooked food and cross-contamination during preparation. Norovirus is mainly associated with person-to-person transmission and outbreaks due to contaminated products or infected food handlers.

Both pathogens display yearly seasonal trends with norovirus activity likely directly tied to weather factors such as temperature while Campylobacter infection is indirectly influenced through weather-related changes in human behavior.

Bigger impact on norovirus
Weekly lab report totals for norovirus and Campylobacter between the end of June 2015 and late October 2020 were taken from the national laboratory reporting surveillance system with results reported in the journal PLOS One.

Data on testing for the virus that causes COVID-19, called SARS-CoV-2, in England at diagnostic laboratories were used to indicate the pressure on testing services and the capacity to carry out regular activities.

From March 2020, a reduction was seen in the number of norovirus and Campylobacter laboratory reports but the impact on norovirus was more pronounced. Lab reports of Campylobacter recovered but those of norovirus remained low.

The reduction in norovirus reports was significantly associated with the period after the first death from COVID-19 in the UK in early March. Results for the Campylobacter models were similar.

Norovirus was impacted more during the early months of the pandemic. The effect of the stringency of the COVID-19 control measures was greater for norovirus lab reporting than for Campylobacter. Changes in testing capacity appear to have more negatively impacted norovirus reporting.

Total estimated reduction was 47 percent to 79 percent for norovirus from March to October 2020. The reduction changed for Campylobacter from 19 percent to 33 percent in April to 1 percent to 7 percent in August.

Factors behind decline
The fall in lab reports of norovirus was significantly associated with changes in infection control policies and SARS-CoV-2 virus testing approaches.

Lab testing for norovirus was likely more impacted during the pandemic than that for Campylobacter because of the capacity to get samples for lab confirmation and testing priority.

Due to similarities between norovirus and coronavirus, there is likely to have been a true reduction in norovirus resulting from infection control measures introduced for COVID-19, such as greater handwashing, social distancing and enhanced hygiene in care homes and other healthcare settings.

For Campylobacter, restaurant closures because of the outbreak could have reduced the transmission of infection but there was increased food preparation in the home.

Another factor was a change in healthcare-seeking behavior during the pandemic as norovirus and Campylobacter differ in clinical severity and duration of illness. Patients with Campylobacter infection may have been more likely to contact healthcare providers and have a sample taken for lab diagnosis and pathogen confirmation.

Scientists could not estimate the proportion of the impact attributed to factors such as a genuine reduction in transmission and changes in healthcare-seeking behavior.

Researchers said the study underlines the different impacts a pandemic may have on surveillance of gastrointestinal infectious diseases and how efforts to control one thing can affect others.

“This adds to the need for pandemic preparedness to include consideration of the maintenance of priority routine surveillance systems and the resource to analyze surveillance data during the pandemic period. The direct as well as indirect effects of the pandemic could, through impairing essential surveillance functions, impede the ability to detect ongoing threats to national or international public health.”

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