Three asylum seekers have tested positive for coronavirus in a sprawling border encampment, marking the first cases in a settlement that advocates have long viewed as vulnerable amid the pandemic. Since confirmed cases of coronavirus in Mexico began rising in March, advocates and government officials have worried about the potential for an outbreak in the Matamoros camp, where an estimated 2,000 migrants live in tents on the banks of the Rio Grande river. “For months, public health experts have sounded the alarm that people in these under-resourced migrant encampments and shelters … face disproportionate risks from Covid-19,” said Michele Heisler, the medical director at US-based non-profit Physicians for Human Rights. Global Response Management (GRM), a non-profit providing medical services in the camp, said on Tuesday it is proactively testing and isolating all close contacts of the three migrants who tested positive. “We have five patients in isolation: two who are awaiting results of testing and three who have tested positive on antibody testing,” said the GRM executive director, Helen Perry. “We are taking an aggressive approach to contact tracing and isolation in the hopes that we can catch infections early and prevent potential spread as much as possible.” A spokesman for US Customs and Border Protection (CBP) said its staff is working to “protect America’s borders, slow the spread of the virus and facilitate the cross-border flow of food, medicine and other essential commerce”. Many migrants in the camp were sent to Mexico as they wait for the outcome of their asylum cases in a controversial Trump administration policy officially known as “Migrant Protection Protocols” but commonly referred to as the Remain in Mexico program. To prepare for the virus, GRM said it worked with local officials to carry out measures such as checking the temperature of anyone who enters the camp and building a 20-bed field hospital. After the group disclosed the first confirmed case, two more migrants tested positive on Tuesday, Perry said. Luz, a 42-year-old asylum seeker from Peru who asked that her last name not be used due to safety concerns, said she was tested earlier this month after a friend got sick. Both women tested negative. Luz has tried to isolate as much as possible, though she sometimes leaves her tent for relief from the fierce Matamoros heat. “I truly am not afraid, though I try to be cautious,” she said. “But you can’t stay in your tent all the time. It’s too hot.”