A church is the center of an outbreak in Vietnam’s largest city.

For more than 20 years, the husband and wife were stalwarts of their evangelical community in southern Vietnam: pastors of a small Protestant church where they distributed food and clothing to the needy of Ho Chi Minh City.

Now, the couple are pariahs. They have been blamed by the authorities for a major coronavirus outbreak, are facing a criminal investigation and have been held accountable on social media for a lockdown in their neighborhood and a ban on religious services nationwide.

The couple, Phuong Van Tan and Vo Xuan Loan, who are hospitalized with Covid-19, are accused of allowing parishioners to pray together without wearing masks, a violation of coronavirus protocols that officials say resulted in an outbreak in May linked to more than 200 cases.

Health officials believe that the outbreak started with Ms. Loan, who traveled to Hanoi, the capital, in late April and began experiencing symptoms about two weeks later. They contend that churchgoers gathered in close quarters for their services, did not wear masks and did not report their illnesses.

“These days, in our hospital beds, we grieve both physically and mentally about what is going on,” Mr. Tan, 60, wrote in a Facebook post, in which he asked for forgiveness. “On behalf of the entire church, my wife and I, as pastors, would like to sincerely apologize to all the community.”

Ms. Loan, 65, contradicted the official account of her illness. She believes that she contracted the virus after returning from Hanoi and was not the source of the cluster. She also denied that parishioners had gathered without wearing masks.

“I am the one who always asked people from my church to wear a mask,” she said by phone from the Hospital for Tropical Diseases in Ho Chi Minh City, where she is being treated. “I brought masks to all the people of the church and to people in the community.”

Vietnam kept the coronavirus at bay for more than a year. But the church cluster, outbreaks at factories in the country’s north and the emergence of a troubling new variant all suggest that the country’s luck might be running out as the virus resurges in parts of Southeast Asia. More than half of Vietnam’s 7,800 cases have occurred in the past month.