The coronavirus pandemic has been detected in one of the camps in southern Bangladesh that are home to more than one million Rohingya refugees.
An ethnic Rohingya refugee and another person had tested positive for COVID-19, a senior Bangladeshi official and a UN spokeswoman said.
It was the first confirmed case in the camps, which are more densely populated than most crowded cities on earth.
“Today they have been taken to an isolation centre after they tested positive,” Mahbub Alam Talukder, the Refugee Relief and Repatriation Commissioner, told Reuters.
The other patient was from the “host population”, a term usually used to refer to locals living outside the camps, the UN spokeswoman said.
In early April, authorities imposed a complete lockdown after a number of cases were found in Cox’s Bazar district, restricting all traffic in and out of the refugee camps.
Bangladesh authorities also forced aid organisations to slash their camp presence by 80 percent.
Rights groups have expressed concerns that the camps are hotspots of misinformation about the pandemic because of an internet ban imposed last September.
As many as 60,000-90,000 people are jammed into each square kilometre, with families of up to a dozen sharing small shelters.
More than 730,000 Rohingya arrived from Buddhist-majority Myanmar in late 2017 after fleeing a military crackdown.