Experts and activists have warned that about one million Rohingya refugees living in the crowded and cramped camps in Bangladesh's Cox's Bazar are vulnerable to coronavirus infections.
The wretched conditions in the camps, where most of the Rohingya Muslims arrived in 2017 to escape a Myanmar military crackdown across the nearby border, are fertile ground for any disease, experts say.
The public in other countries is being told to keep two metres (six feet) apart. That is the width of most paths in Kutapalong, the world's biggest refugee camp with 600,000 Rohingya, that are clogged each day with people out on the daily hunt for food and fuel.
Masks that have become a daily essential in much of the world are rarely seen. Sanitiser is unheard of.
Each shack is barely 10 square metres (12 square yards) and they are overcrowded with up to 12 people.
"You can hear your next-door neighbour breathing," said one aid worker.
Social distancing is "virtually impossible" in the camps, Bangladesh head of Doctors Without Borders (Medecins Sans Frontieres, or MSF) Paul Brockman said
"The scale of the challenge is immense. Vulnerable populations such as the Rohingya will likely be disproportionately affected by COVID-19," the illness caused by new coronavirus, he told AFP news agency.
Bangladesh has reported only a handful of coronavirus deaths and less than 50 cases but the public and experts fear there are many more.
The Rohingya barely know about the disease as the government cut off most of their access to the internet since late last year under measures to clamp down on the refugees.
Fears have mounted, though, since a Rohingya family of four who returned from India last week was quarantined at a UN transit centre for testing, officials said.
A Bangladeshi woman in nearby Cox's Bazar has also tested positive for new coronavirus, adding to the numbers.
"We are extremely worried. If the virus reaches here, it will spread like wildfire," said Rohingya community leader Mohammad Jubayer.
"A lot of aid and local community workers people enter the camps every day. Some diaspora Rohingya have also returned in recent days. They may be carrying the virus," he said.
Camp resident Lokman Hakim, 50, expressed deep concern at the lack of preventive measures in the camps.
"We have received soap and been told to wash our hands. And that's it," Hakim said.