A Discrete-Time Sequential Test for Constant Fatality Rate of an Emerging Epidemic with Applications to Severe Acute Respiratory Syndrome in Hong Kong and Beijing

• Activity Number: 315
• Type: Contributed
• Date/Time: Tuesday, August 5, 2008 : 2:00 PM to 3:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Ying Xu*+ and S. F. Yip and K. F. Lam
• Companies: The University of Hong Kong and The University of Hong Kong and The University of Hong Kong
• Keywords: fatality rate ; martingale difference ; sequential test ; severe acute respiratory syndrome (SARS)

Abstract

During the course of an emerging epidemic, the fatality rate is a popular quantitative index to measure the lethality of the disease and to address the severity of the epidemic. In general, a decreasing fatality rate over time reflects the effectiveness of the clinical treatment, whereas a constant one may indicate the futility. A discrete-time sequential test, built with the martingale difference approach and using the daily aggregated data of deaths and recoveries, is proposed for testing the hypothesis of a constant fatality rate, against a decreasing one, in a timely manner throughout the outbreak of an infectious disease. Simulation studies showed that the proposed test performs well and is extremely sensitive in picking up the decreasing fatality rate over time. The severe acute respiratory syndrome (SARS) data in Hong Kong and Beijing are also used for illustration.