An outbreak of the bubonic plague has killed 20 villagers in Madagascar, health officials confirmed on Wednesday. The outbreak, which is one of the worst in years, took place in the town of Mandritsara. Experts are worried the disease could spread, both because living standards in the country have plummeted and because it occurred outside the country’s normal plague season. Last year, an estimated 60 people died in Madagascar from bubonic plague, the largest number in the world. The disease is caused by bites from black rat fleas.