With cramped living conditions, poor hygiene infrastructure, and a lack of health-care facilities, the camps in Cox’s Bazar, on the coast of the Bay of Bengal in southeastern Bangladesh, have the qualities that make them a tinderbox for the spread of the virus. But it is not just there that alarm is growing over an outbreak erupting among refugee and displaced communities. Of the about 25.9 million refugees globally, more than three-quarters live in developing countries, where health-care systems are already weak and, in some cases, where humanitarian crises are ongoing, further compounding risks. In Kenya and on Greek islands, in northwestern Syria and along the U.S.-Mexico border, some fear that an outbreak of a disease even wealthy countries have been unable to halt would prove catastrophic.

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Refugees “have lost all of what is needed to defend yourself against the virus,” Jan Egeland, the secretary-general of the Norwegian Refugee Council, told me. “The displaced have lost their homes, their communities, their space, their hospitals.” Egeland warned in March that the virus could “decimate” refugee groups if preventative measures were not taken. (Last month, the United Nations appealed for hundreds of millions of dollars to mitigate the risk of the coronavirus spreading among displaced people.) Driven from their home by war, violence, or natural disasters, he said, displaced people have been forced to seek refuge in areas they believed to be out of the way of danger. “They have crowded these places that they thought were safe,” he said, “and now, of course, these are the places that can be the most unsafe places possible.”

In Cox’s Bazar, a patchwork of 34 refugee camps houses about 855,000 refugees, and more than 400,000 Bangladeshis live in close proximity to the camps. A risk report on the possibility of the spread of the coronavirus in the Cox’s Bazar camps produced in March by ACAPS, a Norwegian humanitarian-analysis group, found that the population density in the camps averages 40,000 people per square kilometer, but increases to 70,000 in the most cramped areas. By comparison, ACAPS said, the overall population density in Wuhan, China, the epicenter of the coronavirus outbreak, is 6,000 people per square kilometer. Since being hastily erected in 2017, the Cox’s Bazar camps have precariously survived despite nearly constant threats from monsoon floods, cyclones, and rampaging elephants, but the spread of the virus would be the “worst nightmare come true,” Egeland said.

The camps’ density, combined with their poor infrastructure, makes it hard to follow much of the advice coming from experts on how to slow the spread of the virus, such as maintaining distance from one another. “The measures which all health experts globally are putting forward are social distancing and isolation, which are simply not an option,” says Deepmala Mahla, the Asia director for CARE, a humanitarian agency with more than 1,000 staff members in Bangladesh, including some 450 in the Cox’s Bazar camps. Mahla told me that many people in the camps suffer from poor nutrition and have underlying health issues. Wash areas and public toilets are often crowded, with women in particular standing in long lines. “The situation is so risky, I shudder to think what could happen,” Mahla said.