Weekly COVID-19 cases have risen over the last five weeks.
More schools across the United States are putting mask mandates in place as COVID-19 cases continue to rise.
Before winter break, districts in New Jersey and Pennsylvania announced they would temporarily be requiring masks among students and staff members amid a surge of respiratory illnesses.
Now schools in Massachusetts and Michigan are following suit while Chicago schools are asking students to take rapid tests before classes start.
Chelsea Public Schools in Boston announced in a letter to the community that the decision was due to Suffolk County designated as "high risk" for COVID-19 transmission as defined by the Centers for Disease Control and Prevention.
"As a result of this designation, Chelsea Public Schools will implement a mask mandate, effective on Monday, January 9," Superintendent Dr. Almi G. Abeyta wrote in the letter. "Masks must be worn in school buildings at all times except when eating or drinking…Mask wearing will continue to remain mandatory for any person visiting our school health offices, and anyone returning to school from a five-day quarantine following a positive COVID-19 diagnosis."
The letter did not state for how long the mandate would be in place.
Meanwhile, Ann Arbor Public Schools in Michigan said it was instituting a two-week mandate staring Monday, Jan. 9, and ending Friday, Jan. 20.
According to local affiliate WXYZ, the decision comes after a wave of respiratory illnesses led to at least five school closures in December alone.
"The Ann Arbor Public Schools will require well-fitting masks to be worn by students, staff and visitors while indoors in AAPS schools, beginning on January 9th and during the first two weeks following the winter break," Superintendent Jeanice Kerr Swift wrote in a letter to families, students and staff. "Extra masks are available at all school buildings for use by students and staff."
Additionally, Chicago Public Schools announced it is asking students and employees to perform a rapid at-home COVID-19 test before entering classrooms.
'In order to keep our school communities safe, please test for COVID-19 before returning to school," the notice read. "If you test positive, please report the positive test using the COVID-19 Self-Reporting Form, and follow the guidance outlined on our safety page."
Data from the CDC shows that COVID-19 cases are increasing even as cases of RSV and influenza are trending downward.
Weekly cases have risen from 309,253 for the week of Nov. 30 to 470,699 for the week of Jan. 4, data shows.
ABC News Ahmad Hemingway contributed to this report.
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