Considerations for Enteric Disease Surveillance in a Post-COVID-19 Pandemic World: A Canadian Perspective

The COVID-19 pandemic has had direct and indirect impacts on many aspects of public health, including enteric disease rates. Multiple countries, including Canada, have documented decreased rates of enteric illnesses compared with prepandemic levels (Bassal et al., 2021; de Miguel Buckley et al., 2020; Dougherty et al., 2023; Hibiya et al., 2022; Lai et al., 2021; Love et al., 2022; Ray et al., 2021; Steffen et al., 2020; Wang et al., 2021), however, the specific reasons for these changes remain unclear.

As we move forward from the acute phase of the COVID-19 response, we begin to wonder about the postpandemic enteric disease landscape, specifically the impact of COVID-19 on virtual care, rapid testing, travel behaviors, and historical comparisons. How will enteric disease surveillance be impacted by these changes in the years to come? And how should we adjust our public health infrastructure and procedures to adapt?

The Rise of Virtual Health Care and Rapid Testing

It is evident that COVID-19 has changed the way patients interact with the health care system and providers. In-person physician visits decreased substantially with the start of the pandemic (Canadian Institute for Health Information, 2021), largely due to fears of exposure to COVID-19 in a clinic or hospital setting, resulting in innovations in virtual care. A heavily burdened health care system also placed restrictions on who could attend an in-person visit, and frequently encouraged patients to seek virtual care if and whenever possible.

In Canada, at the peak of the pandemic, provinces saw up to 70% of all family physician consults conducted virtually (Canadian Institute for Health Information, 2021). With virtual visits experiencing an unprecedented rise to prominence, corresponding decreases in the number of stool specimens collected for laboratory testing are expected.

Equally notable, the COVID-19 pandemic also resulted in the widespread acceptance of rapid testing over more traditional laboratory confirmation. Whether this shift in testing trends will spill over into other diseases remains to be seen. There are currently rapid diagnosis options available for select enteric illnesses that do not require specialized laboratory equipment or training (Pisanic et al., 2019; Strobel et al., 2022). Perhaps postpandemic, we may see newfound innovation in this area, and increased uptake of the existing rapid diagnosis options for enteric pathogens. Both of these shifts in the health care system have the potential to significantly impact enteric disease reporting.

Our current enteric disease surveillance systems are heavily reliant on laboratory confirmation, as well as typing methods that require laboratory isolation, such as whole genome sequencing. If tendencies toward virtual care and innovations in rapid testing continue, alternative approaches may have to be considered to continue to monitor trends and assess burden of illness. Some of these approaches could include monitoring pharmacy sales of antidiarrheal drugs, crowdsourcing illness complaints, analyzing search engine trends for key words, and calculating new under-reporting estimates for various pathogens. Although these approaches are not novel, a movement away from traditional laboratory confirmation could see them gain prominence in our surveillance systems.

The Advent of Revenge Travel

Another notable impact of the COVID-19 pandemic was the temporary pause to most international travel. With the reduction in Canadians traveling internationally, a substantial decrease in the reported number of travel-acquired enteric illnesses was also observed (Dougherty et al., 2023). As restrictions on nonessential travel were lifted as part of the gradual easing of pandemic measures, the term “revenge travel” became popular jargon to describe the expected spike in travel activity as people “made up for lost time.”

Although it was unlikely that the number of reported travel-acquired cases of enteric illness would remain at the historically low rates observed during the acute phase of the pandemic, it is of interest to public health to monitor the extent of the expected rebound; will the number of travel-acquired enteric infections return to, or perhaps exceed, prepandemic levels? If there is a substantial increase in the number of travel-acquired enteric illnesses in the months and years to come, we must ensure that our public health surveillance and response systems are prepared to respond accordingly.

The impacts of the COVID-19 pandemic may have other consequences on how travelers view potential health risks associated with international travel. Are Canadian travelers now more aware of infection prevention measures after the pandemic, and could this cause an increase in handwashing, sanitization, pretravel vaccination, and caution surrounding food and water quality while traveling outside of Canada?

Conversely, could the widespread misinformation and vaccine hesitancy that has been observed surrounding COVID-19 vaccinations cause fewer travelers to seek out public health travel advice before planning an international trip, and preventative treatment options such as the Hepatitis A vaccine? The past 2 years provide a unique opportunity to further investigate the burden of enteric-related illnesses associated with international travel.

Disruptions to Historical Comparisons

As we accelerate our journey into a postpandemic world, it will be important to monitor health care-seeking behaviors, testing practices, and international travel trends among the public to be able to contextualize changes in reported enteric surveillance data. However, the monitoring of trends itself, as an analytic exercise, has also been impacted by COVID-19. A common practice for aberration detection in public health is comparing the currently observed incidence of a pathogen to a historic reference period, such as the average incidence over the previous 5 years.

However, how useful are these reference periods considering COVID-19's significant impact on 2020 and 2021 enteric illness data? What adjustments will we need to make to interpret the trends we see in 2023, 2024, and beyond? Or will we need to compare against a 2017–2019 historic baseline for future trend analysis? This issue of how to conduct historical comparisons is something that requires further investigation and contemplation as the solution may differ between pathogens and contexts.

The mentioned examples are just some considerations as to the impacts the COVID-19 pandemic has had on enteric disease surveillance and response. Although these considerations are presented from the Canadian perspective, they are certainly relevant internationally and could provide an opportunity for further international collaboration, to deepen our collective understanding of how this monumental event in public health has changed, and will continue to change, the global enteric disease surveillance landscape moving forward.