In those sessions, Mr. Krumroy identified the association of trauma with relief-seeking behaviors, like drinking and using drugs, that has scarred so many members, himself included. For him, the trauma that led to his own excess drinking was the AIDS epidemic, when he lived in San Francisco during the height of the crisis. Now he is fighting to quell the reverberations that the coronavirus pandemic is setting off.

“These Google groups and individual phone calls are going to be crucial to helping us all acknowledge how traumatic the coronavirus potentially is,” Mr. Krumroy said. “We need to tell each other that our reactions are normal and understandable and not something to be ashamed of. And with that mutual support, I’m hopeful that most of us will be able to resist any urge to re-engage in our behavior.”

But Kristen Marshall, who manages the DOPE Project in San Francisco for the national Harm Reduction Coalition, is not nearly as hopeful. To help prevent overdoses, the project distributes clean syringes, addiction medications like naloxone and Narcan, snacks and water bottles to programs working directly with people without housing. She is considered an essential worker who does not have to heed the state’s orders to shelter in place, so she is moving about the city with other health workers, to aid people without housing who are suffering from addictions and health crises, ordered to scatter, their belongings confiscated.

“Closing or limiting programs designed to support them puts them at even higher risk for overdose and overdose death,” Ms. Marshall said.

She added: “For so many of our folks, their contact with our programs are some of their only opportunities for socialization and connection. So workers and their organizations are desperately trying to balance keeping themselves healthy and safe while also refusing to close their programs’ doors.”

The business shutdown orders rolling through the country are hitting some in the recovery community in ironic ways. On the Facebook group Harm Reduction Abstinence Moderation Support, which accepts many people who handle substance issues by reducing use instead of abstaining, some worry that with some liquor stores closing, they will have to withdraw cold turkey and plunge into delirium tremens — or the “DTs,” with hallucinations, vomiting, fever and high blood pressure. And then they fear they won’t be admitted into overcrowded emergency departments. Or will be exposed to Covid-19 in those waiting rooms.

“Many of our members have laid in a supply of alcohol so they won’t crash immediately,” said Kenneth Anderson, the founder of the group.