The border between Thailand and Myanmar is more than 1,500 miles long, much of it thickly forested. Myanmar has suffered runaway transmission of the coronavirus. Thailand, so far, has not.
But over the past couple of weeks, at least 19 Covid-19 cases in Thailand have been linked to migrant workers who slipped between the two countries undetected. The infections have spooked Thai officials, who have managed one of the world’s most successful coronavirus containment strategies.
The health authorities in Thailand are now racing to trace the contacts of hundreds of people who may have been exposed to the virus. And the events have cast a spotlight on how regions like Southeast Asia that depend on porous borders are fighting to keep the virus out while allowing economic activity to continue.