Comparability of Results from Pair and Classical Model Formulations for Different Sexually Transmitted Infections

Authored by Jimmy Boon Som Ong, Xiuju Fu, Gary Kee Khoon Lee, Mark I-Cheng Chen

Date Published: 2012

DOI: 10.1371/journal.pone.0039575

Sponsors: Singapore National Medical Research Council

Platforms: Java

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

The ``classical model'' for sexually transmitted infections treats partnerships as instantaneous events summarized by partner change rates, while individual-based and pair models explicitly account for time within partnerships and gaps between partnerships. We compared predictions from the classical and pair models over a range of partnership and gap combinations. While the former predicted similar or marginally higher prevalence at the shortest partnership lengths, the latter predicted self-sustaining transmission for gonorrhoea (GC) and Chlamydia (CT) over much broader partnership and gap combinations. Predictions on the critical level of condom use (C-c) required to prevent transmission also differed substantially when using the same parameters. When calibrated to give the same disease prevalence as the pair model by adjusting the infectious duration for GC and CT, and by adjusting transmission probabilities for HIV, the classical model then predicted much higher C-c values for GC and CT, while C-c predictions for HIV were fairly close. In conclusion, the two approaches give different predictions over potentially important combinations of partnership and gap lengths. Assuming that it is more correct to explicitly model partnerships and gaps, then pair or individual-based models may be needed for GC and CT since model calibration does not resolve the differences.

Tags

Epidemiology Dynamics networks Women Diseases Gonorrhea Sex workers Chlamydia-trachomatis infection Hiv-1 transmission Condom use