A Mongolian man known as Citizen T and his pregnant wife died on April 27th and 30th after an outbreak of the Bubonic plague, which wiped out half of Europe’s population. They had consumed contaminated marmot, a large species of squirrel that is banned from consumption as it is known to carry the plague bacteria. The couple had hunted the rodent as its meat is believed to be a folk remedy. They leave behind four orphaned children.

The couple had been traveling on a commercial plane, which arrived from the Mongolian towns Bayan, Ulgii, and Khovd to the capital, Ulaanbaatar. Emergency responders dressed in anti-contamination suits immediately boarded the plane, ready to carry out on board checks and escort the possibly infected passengers. While most were examined at the airport, 11 passengers in immediate contact with the couple were held for urgent hospital checks. More than 100 people came into contact with the couple, all of whom have been put under intensive medical supervision. Many of these people were foreign tourists and were not allowed to leave the area until many days later. Necessary security precautions were taken to contain the infection, including quarantining the entire city and closing a key border between Russia and Mongolia.

While the Bubonic plague is rare, it is still fatal, able to kill an adult in less than 24 hours if left untreated. The disease can be treated with antibiotics, but it is crucial to avoid touching dead animals exposed to the plague. The World Health Organization reports that 584 out of 3,248 cases from 2010 to 2015 have resulted in death. Cases of the plague and quarantines have been recorded in China, the US, countries in Africa, and many more.

The tourists trapped in the city have been forced to make the most of their extended trip, and have posted updates to social media.