Led by @fanohi.bsky.social, and co-supervised by @scauchemez.bsky.social, this study is the result of a fruitful collaboration between Institut Pasteur Madagascar and @pasteur.fr.

Finally, we evaluated intervention strategies and found that targeting both rats and their fleas at the start of the epidemic season (July–Sep) was the most effective way for reducing human plague cases. This proactive strategy contrasts with the reactive measures currently used in Madagascar.

We estimated that the rat-to-rat reproduction number peaks at 1.45 (95%CI: 1.41, 1.48) in Oct., whereas human cases peak in Dec.–Jan. Only 0.5% (95% CI: 0.2%, 0.9%) of rats are infected each season, suggesting that plague is not the main driver of rat population changes.

Models that incorporated seasonal fluctuations in rat and flea populations performed better than those that did not, indicating that rat and flea population dynamics are key drivers of human plague outbreaks.

Plague is usually transmitted to humans by bites from fleas that live on rats. From Dec 2018 to Jun 2020, rats were trapped in plague foci, fleas counted, and rats tested for plague antibodies. We built 5 rat–flea–human transmission models and fitted them to our field data and to human cases.