In what could be an ominous sign that new coronavirus cases are soon to accelerate in metro Detroit, officials with Detroit Public Schools said Saturday night that a teacher at Osborn High School was the district's first confirmed case.

Superintendent Nikolai Vitti said the district learned of the diagnosis from the Detroit Health Department.

"The individual has been released from the hospital and is OK and is self-quarantined at home," Vitti said in a letter to district staff obtained by the Free Press. The letter goes on to suggest that the entire Osborn High School "learning community" of 900 students, teachers and other staff should "self-quarantine for 14 days" — meaning, stay at home for two weeks and strictly limit any contact with other people.

"The staff member has decided to protect their identity," Vitti's letter said.

He went on: "This will unfortunately not be our only case. It is likely that other individuals at schools or at the district level have or will develop COVID-19. If you think you have been exposed to COVID-19 and develop a fever and symptoms, such as cough or difficulty breathing, call your healthcare provider for medical advice."

Detroit health officials said they agreed with Vitti’s suggestion for those who recently were at Osborn High School to isolate themselves.

“Students and faculty who were physically in Osborn school and may have had primary contact with the infected faculty member should quarantine for 14 days … ,” said a news release issued late Saturday by the Detroit Health Department.

The district used all available means of communicating the warnings, said Detroit Public Schools spokeswoman Chrystal Wilson. That meant reaching all of Osborn's students, faculty, administrators and other employees on Saturday.

“A robo call went out to Osborn (and) to the District, and a text was sent to all families and staff. Also, we posted the update and confirmation on our website where we will continue to do so when we receive confirmations,” Wilson said in an email to the Free Press.

In addition to the Detroit school teacher, three more "presumptive positive cases" of COVID-19 were identified Saturday in Oakland County. Here are patient counts as of Saturday night.

The number of people who have tested positive for the coronavirus in Michigan now stands at 33, the state announced in a news release on Saturday.

That’s up from the 25 known in the state as of Friday evening. Gov. Gretchen Whitmer announced the new count in a press release Saturday evening.

In each case, officials have said specimens will be sent to the Centers for Disease Control and Prevention for confirmation.

SYMPTOMS: COVID-19 can appear in as few as two days or as long as 14 after exposure, officials say. Symptoms include fever, cough and shortness of breath, according to health officials. State health officials have urged residents to wash hands frequently, practice social distancing and avoid crowds, among other recommendations.

The state has set up a hotline at 888-535-6136 to answer health-related questions about the virus, 8 a.m.-5 p.m. daily.

Contact: blaitner@freepress.com