The potential for sexual transmission to compromise control of Ebola virus outbreaks

Abstract

Recent evidence suggests that sexual contact may give rise to transmission of Ebola virus long after infection has been cleared from blood. We develop a simple mathematical model that incorporates contact transmission and sexual transmission parametrized from data relating to the 2013-2015 West African Ebola epidemic. The model explores scenarios where contact transmission is reduced following infection events, capturing behaviour change, and quantifies how these actions reducing transmission may be compromised by sexual transmission in terms of increasing likelihood, size and duration of outbreaks. We characterize the extent to which sexual transmission operates in terms of the probability of initial infection resolving to sexual infectiousness and the sexual transmission rate, and relate these parameters to the overall case burden. We find that sexual transmission can have large effects on epidemic dynamics (increasing attack ratios from 25% in scenarios without sexual transmission but with contact-transmission-reducing behaviour, up to 80% in equivalent scenarios with sexual transmission).

Persistent Marburg Virus Infection in the Testes of Nonhuman Primate Survivors

“…Therefore, a single case of filovirus persistence in a survivor of filovirus disease could pose a high risk for new outbreaks and considerable loss of lives. Indeed, such unconventional filovirus transmission chains originating from persistently infected survivors occurred during the 2013-2016 EVD outbreak (Arias et al, 2016;Blackley et al, 2016;Diallo et al, 2016;Lee and Nishiura, 2017;Mate et al, 2015;Sow et al, 2016;Uyeki et al, 2016;Vinson et al, 2016). Consequently, understanding the mechanisms that allow filoviruses and other RNA viruses to persist in survivors is of utmost importance for the development of MCMs to abolish chronic filovirus infection.…”

“…EBOV genomic RNA has been repeatedly detected in semen of EVD survivors (Deen et al, 2017;Diallo et al, 2016;Eggo et al, 2015;Rodriguez et al, 1999;Rowe et al, 1999;Uyeki et al, 2016) and EBOV has been successfully isolated from a few samples (Chughtai et al, 2016;Rodriguez et al, 1999). Sexual transmission of EBOV has also been implicated in the initiation of alternative EBOV transmission chains (Arias et al, 2016;Blackley et al, 2016;Diallo et al, 2016;Lee and Nishiura, 2017;Mate et al, 2015;Sow et al, 2016;Uyeki et al, 2016;Vinson et al, 2016). Filovirus persistence is also hypothesized to cause the plethora of apparent sequelae, including arthralgia, cognitive impairment, headaches, hearing loss, and myalgia, that have been reported in numerous MVD and EVD survivors (Baltzer et al, 1979;Burki, 2016;Carod-Artal, 2015;Epstein et al, 2015;Scott et al, 2016).…”

Sexual transmission and the probability of an end of the Ebola virus disease epidemic

“…In addition to comparing the modeling results with those derived from the WHO criteria, we examined how influential relatively unknown parameters are to determining the week in which the end of an epidemic can be declared. While the relevance of sexual transmission to the overall transmission dynamics has been explored elsewhere ( Abbate et al, 2016;Vinson et al, 2016 ), as has the extinction time of Ebola using a mathematical model ( Abbate et al, 2016;Valdez et al, 2015 ), the present study is the first to model the end of Ebola, explicitly accounting for sexual transmission.…”

“…h ( τ ) was assumed to mirror the survival length of virus positive period, assuming that the frequency of sexual contact remains unchanged over the time since recovery. Let S ( x ) represent the survival probability of Ebola virus RNA in semen in week x since illness onset ( Eggo et al, 2015;Vinson et al, 2016 ), as measured by the duration of viral RNA positive period with mean m . The probability density function (pdf) (or the continuous version) of the se-…”

What Do We Know About Controlling Ebola Virus Disease Outbreaks?

“…136,137 Models have been used to estimate the added impact of sexual transmission or reintroduction into communities thought to be disease free. 138,139 Finally, modellers have estimated the likelihood of disease recurrence in the region, thought to be within 20 years in the absence of vaccination campaigns. 140…”