title: Case and partnership reproduction numbers for a curable sexually transmitted infection.
abstract: Sexually transmitted infections (STIs) are, by definition, transmitted between sexual partners. For curable STIs an infected index case can potentially re-infect the same partner multiple times. Thus, R0, the average number of secondary infections one typical infected individual will produce during his or her infectious period is not necessarily the same as the average number of secondary cases (infected persons). Here we introduce the new concept of the case reproduction number (Rc). In addition, we define the partnership reproduction number (Rp) as the average number of secondary partnerships consisting of two infected individuals one typical infected individual will produce over his or her infectious lifetime. Rp takes into account clearance and re-infection within partnerships, which results in a prolongation of the duration of the infectious period. The two new reproduction numbers were derived for a deterministic pair model with serial monogamous partnerships using infection parameters for Chlamydia trachomatis, an example of a curable STI. We showed that re-infection within partnerships means that curable STIs can be sustained endemically even when the average number of secondary cases a person produces during his or her infectious period is below one.
authors.affiliation: Institute of Social and Preventive Medicine ISPM, University of Bern, Finkenhubelweg 11, 3012 Bern, Switzerland. jheijne@ispm.unibe.ch
authors.forename: Janneke C M
authors.initials: JC
authors.lastname: Heijne
authors.forename: Sereina A
authors.initials: SA
authors.lastname: Herzog
authors.forename: Christian L
authors.initials: CL
authors.lastname: Althaus
authors.forename: Nicola
authors.initials: N
authors.lastname: Low
authors.forename: Mirjam
authors.initials: M
authors.lastname: Kretzschmar
mesh_terms: D000465:Algorithms; D002690:Chlamydia Infections / Q000382:microbiology / Q000635:transmission; D002692:Chlamydia trachomatis / Q000502:physiology; D005260:Female; D054884:Host-Pathogen Interactions; D006801:Humans; D008297:Male; D008954:Models, Biological; D012725:Sexual Behavior; D012747:Sexual Partners; D012749:Sexually Transmitted Diseases / Q000635:transmission*; D013997:Time Factors