Background. Infectious intestinal disease (IID), usually presenting as diarrhoea and vomiting, is frequently preventable. Though often mild and self-limiting, its commonness makes IID an important public health problem. In the mid 1990s around 1 in 5 people in England suffered from IID a year, costing around 0.75 billion. No routine information source describes the UK's current community burden of IID. We present here the methods for a study to determine rates and aetiology of IID in the community, presenting to primary care and recorded in national surveillance statistics. We will also outline methods to determine whether or not incidence has declined since the mid-1990s. Methods/design. The Second Study of Infectious Intestinal Disease in the Community (IID2 Study) comprises several separate but related studies. We use two methods to describe IID burden in the community - a retrospective telephone survey of self-reported illness and a prospective, all-age, population-based cohort study with weekly follow-up over a calendar year. Results from the two methods will be compared. To determine IID burden presenting to primary care we perform a prospective study of people presenting to their General Practitioner with symptoms of IID, in which we intervene in clinical and laboratory practice, and an audit of routine clinical and laboratory practice in primary care. We determine aetiology of IID using molecular methods for a wide range of gastrointestinal pathogens, in addition to conventional diagnostic microbiological techniques, and characterise isolates further through reference typing. Finally, we combine all our results to calibrate national surveillance data. Discussion. Researchers disagree about the best method(s) to ascertain disease burden. Our study will allow an evaluation of methods to determine the community burden of IID by comparing the different approaches to estimate IID incidence in its linked components.
Bibliographical noteFunding Information:
We should like to thank the UK Food Standards Agency for funding the IID2 Study (Project B18021), Julie Dodds, Hansa Shah, Valerie Brueton and Vania Gay at the MRC General Practice Research Framework, Mike van der Es and Lisa Irvine at the University of East Anglia, Kathryn Jackson and Emma Dixon at the University of Manchester, Alan Ridge, Katherine Mather and Bernard Wood at the Health Protection Agency Regional Laboratory in Manchester, Fenella Hal-stead, Dalia Choudhury, Lisa Berry, Corine Amar, Ben Lopman and John Harris at the Health Protection Agency Centre for Infections, Laura Viviani, Suzanne St Rose and Julian Gardiner at the London School of Hygiene and Tropical Medicine, Shirley Large at NHS Direct, Paul Cook for chairing the IID2 Study Executive Committee and Gael O'Neill, our Project Officer at the Food Standard Agency. We should also like to thank all the participants, research nurses, practice staff, telephonists, laboratory, research and administrative staff who are taking part in the IID2 Study.