The Reproduction Number of Hepatitis A in Thailand: a 10 Year-period Estimate Using the National Diseases Surveillance Data

Abstract

The reproduction number, R, is the actual average number of secondary cases per primary case which is the useful information for understanding epidemic. If R exceeds 1, the epidemic is growing, while R less than 1, the epidemic decline or end.  The cases of hepatitis A in the national disease surveillance from 2005 to 2014 were used to estimate the R by a likelihood-based estimation procedure and characterise the epidemic. The results showed that R of hepatitis A in Thailand are varied by provinces. An overall average R was 1.19 (95%CI=1.10-1.28). In endemic areas (low effective transmission), the R was 0.95 (95%CI=0.94-0.97). While in outbreak areas (high effective transmission), the R was 1.29 (95%CI=1.19-1.38). These findings suggest that the control measures for hepatitis A are highly required in the outbreak areas as soon as possible in order to control the transmission of hepatitis A viruses. However, estimation of R from epidemic curves can be underestimate as those asymptomatic infections were not included.