A dengue transmission model in Thailand considering sequential infections with all four serotypes

Abstract

Background: Dengue fever/dengue haemorrhagic fever is prevalent in Thailand, where all serotypes are found and the dominant serotype has changed irregularly. Although almost all primary infections present with slight symptoms or are asymptomatic, little is known about the infectiousness of dengue fever. Methodology: A mathematical model of the transmission for dengue virus was constructed covering the possibility of sequential infections with all four different serotypes. The model was combined with the seasonal population dynamics of Aedes aegypti, the principal vectors of dengue virus in Thailand. The contributions of inapparent cases in the transmission to mosquito vectors and antibody-dependent enhancement were incorporated into the model. Moreover, the hypothesis of an "unnatural" infection route was examined, where a person acquires immunity by infection during a cross-immunity period, through model simulations. Results: A comparative study on the transmission probabilities of inapparent cases to mosquito vectors showed that the prevalence of dengue infection could be immediately stamped out after a severe outbreak if inapparent cases had no infectiousness. The simulation under an "unnatural" infection route assumption resulted of yearly changes in the dominant serotype and sharp, irregular variations in outbreaks. Conclusion: The supposition that inapparent cases had no infectiousness was not in accord with the actual situation in Thailand. Furthermore, the simulation result supported the "unnatural" infection route as having an influence on epidemics of dengue.

Update on the global spread of dengue

“…These reports have been able to differentiate cases of primary infection from reinfection, showing that 87% of cases in Thailand are reinfections and only 13% are primary infections. This observation allows us to understand the degree of hyperendemic transmission in the region [27,28].…”

On the dynamics of simultaneous spreading of two-strain dengue serotypes

“…Following the empirical observations of Chicaki (Chicaki and Ishikawa, 2009) and Castanha (Castanha et al, 2013) about the serotype frequency occurrences we assume an asymmetry in the initial susceptible host population and solve the model using as initial condition a naive population S h (0, 0) < H, and cross-immune populations S h (i, 0) ≥ 0 togheter an asymmetry expressed by the condition S h (1, 0) = S h (2, 0).…”

“…They concentrated in the analysis of stability of the equilibruim points and established the conditions for the coexistence of two different serotypes in the same population based on the indirect interaction between these serotypes through the immunological memory expressed by the ADE. Chicaki and Ishikawa (Chicaki and Ishikawa, 2009) presented a dengue model considering sequential infections for different serotypes to simulate dengue transmission in Thailand. Their model takes into account sazonality effects in vector population, existence of unapparent cases, ADE and variability in the transmission probabilities for each serotype.…”

Dynamical Model for Determining Human Susceptibility to Dengue Fever

“…All of the four dengue viruses co-circulate in many areas of Africa, the Americas and Asia, the dominant serotype has changed irregularly (Chikaki and Ishikawa, 2009). Infection with one serotype confers permanent immunity against that serotype but only temporary and partial protection against the other three serotypes and secondary or sequential infections are possible after a short time (Rodenhuis-Zybert et al, 2010).…”