Transmission dynamics and epidemiology of dengue: insights from age-stratified sero-prevalence surveys

The relationship between infection with the four major serotypes of dengue virus and the occurrence of different forms of disease is complex and not f ully understood. Interpreting longitudinal records of the incidence of seri ous disease to gain insight into the transmission dynamics and epidemiology of the virus is therefore complicated. Since age reflects duration of expo sure, age-stratified, strain-specific serological surveys carried out at on e point in time, or over a short time interval, can potentially provide a r ich source of information on longitudinal patterns. This paper describes th e development and application (to data collected in Thailand) of statistica lly rigorous methods designed to estimate time-varying, strain-specific for ces of infection, and thus basic reproduction numbers, from cross-sectional serological data. The analyses provide support for the:hypothesis that ant ibody-dependent enhancement of transmission influences observed epidemiolog ical pattern. Age-stratified serological data also reveal evidence of a pro pensity for the annual incidence of infection to oscillate over time with a frequency of several years. The latter observation is consistent with the predictions of simple mathematical models of the transmission dynamics of t he virus. The estimates of the basic reproduction numbers obtained are simi lar in magnitude for each dengue serotype, being in the range of four to si x. Such values are higher than those obtained from earlier analyses, and th e implications of this for dengue control are discussed.