Real-Time Estimation of the Case Fatality Ratio and Risk Factors of Death

During the course of an epidemic, estimating the risk of death and identifying risk factors of death are of utmost importance for public health assessment of the severity of infection. The real-time estimation involves a number of important statistical problems to consider, and this chapter comprehensively describes commonly used estimation methods and their pitfalls. When estimating the case fatality risk (CFR) during the course of an epidemic, the data are right-censored because of the time delay from illness onset to death. A conventional survival analysis technique is employed for addressing right censoring. Identification of risk factors of death also requires the care for censored nature of the data, and we have devised a method that combines the survival analysis and logistic regression. Ascertainment bias is always a practical issue in interpreting the absolute value of the CFR or comparing CFR between different groups, and recent studies have shown that observational effort including seroepidemiological survey has to be made to overcome this bias.