The entire school, around 750 students and staff, are now classed as close contacts have been told to remain in strict self-isolation.
A handful of students from Lynfield College and Mt Albert Grammar are considered casual contacts after riding the school bus with Marist students while they were infectious.
Brown said he fell ill on March 20, after attending an event at the Catholic girls' school.
The number of Covid-19 clusters - cases linked because they have been in the same place together- has doubled since Monday.
Most of the clusters were linked to overseas travel and contact with already confirmed cases, director-general of health Dr Ashley Bloomfield said.
Six clients from dementia group Alzheimers Marlborough have tested positive, forcing staff into self-isolation.
There are now 647 confirmed and probable cases of Covid-19 nationally, with 58 new cases announced on Wednesday.
The new cases are made up of 48 new confirmed and 10 probable Covid-19 cases.
Anne Guenole died of the virus on Sunday morning. The 73-year-old was admitted to Grey Base Hospital in Greymouth on Wednesday with suspected influenza.