Observational Research in Childhood Infectious Diseases (ORChID): a dynamic birth cohort study

Lambert, Stephen Bernard; Ware, Robert S; Cook, Anne L; Maguire, Frances A; Whiley, David M; Bialasiewicz, Seweryn; Mackay, Ian M; Wang, David; Sloots, Theo P; Nissen, Michael D; Grimwood, Keith

For peer review only -http://bmjopen.bmj.com/site/about/guidelines.xhtml 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 and drinking water supplies, good personal hygiene standards, widespread vaccine use, and access to high quality medical care, infectious diseases remain the most common cause of significant morbidity, and occasionally mortality, in early childhood. [1] [2] [3] [4] [5] [6] Our current understanding of the epidemiology of early childhood infections is limited by reliance on community-based data from decades ago using low sensitivity diagnostic methods, [7] [8] [9] and more recent studies that primarily focus on severe, hospital-managed disease. 10 11 Much of what we know, especially with newly discovered agents, originates from hospital-based prevalence studies where more than 80% of cases are less than two years of age, representing the sickest 2-3% of young children seen. Experience with influenza illustrates how easily disease burden can be under-estimated by extrapolating from hospital data. [12] [13] [14] Available community-based studies also have important methodological limitations, such as sampling from highly selected subject populations, lack of adequate control subjects, restricted sampling frequency and observation periods, small subject numbers and/or reporting on only a few or single agents. 13 15-18 A key methodological issue is the use of home visits by health care workers or the requirement for clinic visits for specimen collection. Both are likely to be an imposition on busy families, regardless of the setting, leading to biased estimates of infection events and specimen availability. 19