AUSTIN, Texas (AP) — Hundreds of teachers in the Austin Independent School District have pledged not to return to classrooms Monday when schools reopen for in-person learning for up to 25% of its students.

About 850 teachers said they will remain away out of concern for the threat of coronavirus infection to their students and themselves, said Education Austin, the district’s largest teachers union.

The teachers will remain on the job to teach remotely, as they have since mid-September, said union President Ken Zarifis. Education Austin continues to negotiate with the district on school reopening plans, he said.

Teachers’ fears of returning to their classrooms in the face of the coronavirus threat have spawned a number of social media groups. One is Texas Teachers United Against Reopening Schools, founded by Austin-area high school art teacher Lauren Senibaldi. She initially invited 20 colleagues to join the group. The group now has almost 12,500 members, she said.

“I genuinely think that if we just gave students a stack of books, some art materials and a journal, we could have gone forward with remote learning,” Senibaldi said Friday.

Teachers’ fears of infection with the return to in-person instruction has led to a wave of resignations. Texas teachers who resign during the school year face a one-year suspension of their teaching certificates and possible blacklisting by the district from which they are resigning.

“I don’t want to minimize the risk to students, but it is really dangerous for adults. We tend to be Vitamin D deficient. We tend toward obesity. We have risk from diabetes,” Senibaldi said.

There were 2,729 new confirmed coronavirus cases reported across Texas on Friday, including 62 in Travis County where Austin is located, according to the Texas Department of State Health Services. The state also reported 72 new deaths Friday from COVID-19, the illness caused by the virus.

Texas’ total number of confirmed coronavirus cases since tracking of the pandemic began in March is 756,004 with a death toll of 15,895, the DSHS reported. However, the true number of cases is likely higher because many people haven’t been tested and studies suggest people can be infected and not feel sick.

The state health department also estimated 69,431 active cases of the virus, including 3,227 current hospital patients.

For most people, the coronavirus causes mild or moderate symptoms, such as fever and a cough that clear up in two to three weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia, and death.