Estimation of Pneumonic Plague Transmission in Madagascar, August –November 2017

Discussion Between August and November 2017, Madagascar reported nearly 2500 suspected, probable, and confirmed cases of plague 1. Though plague is endemic in the island country, the annual total is typically about 400 – primarily bubonic – cases 2. Only 15% of cases associated with the August–November 2017 outbreak were bubonic, and an unusually large fraction of pneumonic (pulmonary) plague, which can be spread from person-person, resulted in early exponential growth 1. Given the atypical size and spread of the outbreak, concerns regarding the adequacy of existing interventions for the remainder of the plague season have arisen 3. Here, we describe the transmission dynamics of pneumonic plague in Madagascar from August to November 2017; we then consider the role of control strategies that were deployed to curb the outbreak and discuss their effectiveness. To assess transmission dynamics over time, the Incidence Decay and Exponential Adjustment (IDEA) model was used to estimate the basic reproduction number (R0), discount parameter (d), and observed reproduction number (RObs) at various serial intervals (t) 4,5,6. Given the limited size and scope of previous plague outbreaks in Madagascar (2), the affected population was assumed to be fully susceptible in August 2017. A serial interval length (l) of 3–7 days and an epidemic curve of pneumonic plague cases from the World Health Organization (WHO) were used to parameterize the model (Figure 1A) 7,8. Because initial e...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research