Updating and refining estimates of typhoid fever burden for public health action

Efforts to estimate the global burden of typhoid fever can be traced to a meeting of the Pan American Health Organization in 1984 and publication of the outcome in 1986.1 Although an important first step, the 1984 study was recognised as having a number of limitations including provision of scanty methodological detail, the availability of few source data, exclusion of China from the estimate, and lack of consideration of the age distribution of typhoid fever. Subsequently the global typhoid burden was re-estimated for the year 2000, accounting for growth of the global population, new typhoid fever incidence data from population-based studies and the control groups of vaccine trials, advances in the understanding of the age distribution of typhoid fever and its relation to force of infection, adjustment for blood culture sensitivity, and formalisation of methods for assessment of disease burden.2 Since 2000, an updated review of population-based studies of typhoid fever incidence and data from notifiable disease reports from countries with advanced surveillance systems has been published.3 Incorporating these data, the Institute for Health Metrics and Evaluation (IHME) added their first estimate of disability and death associated with typhoid and paratyphoid fevers in aggregate to the Global Burden of Disease (GBD) 2010 project.4,5 The IHME GBD 2010 estimate could be criticised for insufficient methodological detail for external reproducibility, lack of disaggregation of typhoid and paratyphoid fevers, little description of the age distribution of disease, and the surprising selection of liver abscesses and cysts as the prime disease complication of interest.6