New methodology for estimating the burden of infectious diseases in Europe

Abstract

Mirjam Kretzschmar and colleagues describe the BCoDE project, which uses a pathogen-based incidence approach to better estimate the infectious disease burden in Europe.

Figure 1. The Lexis diagram shows events by age and time.

(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 t.

Figure 2. An outcome tree linking exposure, infection and all sequelae.

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.

Figure 3. Preliminary estimates of the burden of disease in terms of DALYs per 100,000 individuals per year for selected infections in four European countries.

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 Escherichia coli/verocytotoxin-producing E. coli; YLD, number of life years lost due to disability; YLL, number of life years lost due to premature death.