Estimating Epidemiologic Parameters and Transmission Dynamics in the SARS Epidemic

• Activity Number: 184
• Type: Other
• Date/Time: Tuesday, August 5, 2003 : 8:30 AM to 10:20 PM
• Sponsor: ASA
• Author(s): M. Elizabeth Halloran*+
• Companies: Emory University
• Keywords: basic reproductive number ; infectious period ; latent period ; missing data ; SARS ; survival analysis

Abstract

Key quantities for understanding the transmission dynamics of infectious diseases include the duration of the latent and infectious period, how infectious individuals are in various settings and types of contacts as measured by the transmission probability, and the relation between the onset of symptoms and the onset of infectiousness. Of further interest is the case-fatality ratio. The basic reproductive number, Ro, the average number of new infectious cases that one case produces is also a key quantity in understanding how successfully an infectious disease will spread in a susceptible population. For the SARS epidemic, evaluating the effectiveness of intervention measures such as isolation of cases and quarantine of contacts requires estimating the time from onset of infectiousness or symptoms to the time of intervention as well as the potential reduction in contact rates. We present different approaches to estimating these key quantities and some of the estimates obtained for the SARS outbreak. We also discuss demands and limitations in the available epidemiologic data during the SARS outbreak.