The outbreak was caused by a 2019 leak of contaminated waste gas at a pharmaceutical plant that manufactures animal vaccines. The firm was found to be using expired disinfectants, allowing residual bacteria to be released through exhaust gasses. It is thought the leak began in late July and continued until late August last year. In December, it was reported that 181 people at a nearby veterinary research facility had been infected, and in January, authorities revoked the plant’s vaccine production licence. The full scale of the outbreak has not been widely reported until now. In addition to the confirmed 3,245...