A Software Tool for Estimation of Burden of Infectious Diseases in Europe Using Incidence-Based Disability Adjusted Life Years

<div><p>The burden of disease framework facilitates the assessment of the health impact of diseases through the use of summary measures of population health such as Disability-Adjusted Life Years (DALYs). However, calculating, interpreting and communicating the results of studies using this methodology poses a challenge. The aim of the Burden of Communicable Disease in Europe (BCoDE) project is to summarize the impact of communicable disease in the European Union and European Economic Area Member States (EU/EEA MS). To meet this goal, a user-friendly software tool (BCoDE toolkit), was developed. This stand-alone application, written in C++, is open-access and freely available for download from the website of the European Centre for Disease Prevention and Control (ECDC). With the BCoDE toolkit, one can calculate DALYs by simply entering the age group- and sex-specific number of cases for one or more of selected sets of 32 communicable diseases (CDs) and 6 healthcare associated infections (HAIs). Disease progression models (i.e., outcome trees) for these communicable diseases were created following a thorough literature review of their disease progression pathway. The BCoDE toolkit runs Monte Carlo simulations of the input parameters and provides disease-specific results, including 95% uncertainty intervals, and permits comparisons between the different disease models entered. Results can be displayed as mean and median overall DALYs, DALYs per 100,000 population, and DALYs related to mortality vs. disability. Visualization options summarize complex epidemiological data, with the goal of improving communication and knowledge transfer for decision-making.</p></div

BCoDE toolkit: step-wise approach to disease model creation and data input.

<p>BCoDE toolkit: step-wise approach to disease model creation and data input.</p

BCoDE toolkit: options for visualization of the outputs.

<p>BCoDE toolkit: options for visualization of the outputs.</p

Infectious diseases for which burden estimates were derived in the BCoDE project.

<p>STEC/VTEC, shigatoxin-producing <i>E. coli</i>/verocytotoxin-producing <i>E. coli</i>.</p

Preliminary estimates of the burden of disease in terms of DALYs per 100,000 individuals per year for selected infections in four European countries.

<p>The differences seen between countries (A–D) may be due to differences in surveillance and/or to differences in the (distribution of) incidence of infections in populations. STEC/VTEC, shigatoxin-producing <i>Escherichia coli</i>/verocytotoxin-producing <i>E. coli</i>; YLD, number of life years lost due to disability; YLL, number of life years lost due to premature death.</p

The Lexis diagram shows events by age and time.

<p>(A) This Lexis diagram shows the occurrence of infection, disease, and death in individual life histories in the time–age plane. An epidemic outbreak affects several cohorts of individuals at a specific time, but may cause disease burden at different times later on. An age-specific intervention starts at a certain time and affects all cohorts reaching the specific age from that time onward. It does not prevent disease burden from earlier infections. Incidence may cause burden within a time window of observation, but also at later times within the life histories of the affected individuals. (B) Here the Lexis diagram shows the occurrence of influenza cases within the time period of one year. All burden generated by morbidity (red) occurs also within that time period. Burden due to mortality is from deaths occurring in the same year as infection. (C) The Lexis diagram for hepatitis B shows that the burden due to morbidity is spread out over many years following the incident infections in the year starting at time <i>t</i>.</p

A disease outcome tree linking infection and all sequelae.

<p>A disease outcome tree linking infection and all sequelae.</p

An outcome tree linking exposure, infection and all sequelae.

<p>The outcome tree displays how individuals may progress through various stages of infection, disease, and death. The process can be quantified by attaching proportions to the arrows depicting transitions, and durations to the various health outcomes. “R” denotes full recovery from infection and/or disease.</p

Diseases and healthcare-associated infections included in the BCoDE toolkit for DALYs calculation.

<p>Diseases and healthcare-associated infections included in the BCoDE toolkit for DALYs calculation.</p

Assuming a downwards time trend for an infection having symptoms in the same years (a) and for an infection where symptoms occur only after 10 years (b). Note:

<p>Blue rectangles represent the number of infections in the year of infection (exposure to an infection). Green “cans” represent the number of cases with symptoms; where these symptomatic cases occur in the same year as the infection (a.) or a few years later (b.) as indicated by the dashed arrow. The long-term average (e.g. 10-year average) is highlighted by a light blue oval for incidence, and by a light green oval for prevalence. The short-term average (e.g. 3-year average) is represented by a dark blue oval for incidence and purple oval for prevalence.</p