Emergency response personnel boarded a flight that had landed in Ulaanbaatar from the cities Bayan, Uglii and Kohvd after there were suspicions that passengers had been in contact with a man, 38, and his pregnant wife, 37, from Uglii who had died on 27 April from contracting the bubonic plague after eating a marmot. 150 passengers at the airport were examined and eleven passengers from Western Mongolia were sent to the hospital.