JMIR Publications

ABSTRACT

Background:

Studies of infectious intestinal disease (IID) in the UK community have shown that the hidden burden of disease is significant and has increased over time. In the late 2000s, the IID2 study estimated 17 million cases of IID per year in the UK, but only a small proportion of cases present to health care, and those that do are often not tested for the causative organism. The landscape and access to primary care have changed significantly over the 15 years since this estimate, increasing uncertainty around its current accuracy. We present the third IID study conducted in the UK, following the methods of previous studies but also using modern pathogen detection methods and digital platforms for recruitment and follow-up.

Objective:

The study aims to determine the burden of IID in the community, estimate the level of under-reporting in routine practice and the general population, and recalibrate UK national surveillance based on the new incidence rates.

Methods:

The IID3 study comprised participants recruited to three population-based prospective cohorts: • Cohort 1: A prospective cohort to assess illness in the general population. • Cohort 2: A prospective cohort of patients with IID presenting to general practices (GPs). • Cohort 3: Enumeration study of routine practice and monitoring contemporary rates of IID presentation using routine laboratory methods. Microbiological analysis of stool samples in cohorts 1 and 2 included testing for a wide range of causative organisms using a comprehensive set of molecular assays, including pathogen targets not routinely sought by National Health Service (NHS) laboratories. Additional characterisation of pathogens was conducted at national reference laboratories. The incidence rates of IID and organisms detected within cohorts 1, 2 and 3 will be compared with national surveillance systems, both laboratory and syndromic. Descriptive statistics and analysis will allow comparison of IID case rates within each cohort, estimate the overall burden of disease caused by different pathogens, and compare findings to earlier IID studies.

Results:

A favourable ethical opinion was granted on 04 August 2022, and recruitment began in September 2023.

Conclusions:

Since the IID1 and IID2 studies, changes have occurred within national surveillance systems, the NHS structure, and public recommendations about when to consult a GP and where to seek healthcare advice. These changes may have altered the extent of IID reporting and the perceived burden in the community, leading to greater uncertainty about the representativeness of IID2 rates. It is anticipated, the results of IID3 will provide insight into trends in disease incidence over time and help quantify inequalities in community IID. Revised estimates can inform policy related to prevention, including food standards and disease management in the UK. Furthermore, advances in molecular diagnostics significantly enhance pathogen detection, increasing our understanding of the causes of IID.