The woman tested positive for coronavirus and is suspected of having introduced the highly infectious variant of the virus to Belgium.
The woman later sent her daughter to school, forcing the closure of two schools, a series of mass tests and an estimated 5,000 people in quarantine.
The woman’s daughter, who did not accompany her on the trip to Switzerland, became infected with the virus and passed it on to a classmate who passed it on to her mother, a teacher at another school.
Belgian media reports that 1,700 tests are to be carried out in the region of Antwerp on Tuesday, after mass testings were carried out on Monday in Edegem.
Edegem Mayor Koen Metsu, who has also been forced to quarantine, said the situation was “unfortunate”.
“If everyone had followed the rules, we wouldn't be in this situation now.”
Media did not name the Swiss ski resort that the woman attended.
The variant, which was first detected in Britain, is expected to be between 40 and 70 percent more infectious than known variants.