TORONTO -- Ontario residents who want to be tested for COVID-19 must now make an appointment at a hospital, assessment centre or pharmacy.

The new province-wide rule was announced Friday amid reports of six-hour wait times and a record-high backlog in test processing.

Here’s what you need to know:

All walk-in testing services at Ontario assessment centres were stopped on Sunday in order to give the province’s lab network a chance to catch up on their backlog of nearly 80,000 tests and to allow time to prepare for the new system.

The appointment-only COVID-19 testing will begin on Tuesday.

In the meantime, while some assessment centres are offering appointments Monday, others were closed due to the transition, meaning that residents have been unable to walk in for a test or book an appointment.

A spokesperson for the Ministry of Health said that "assessment centres were asked to discontinue walk-in testing services" on Monday.

"As this is an operational change for walk-in sites only, all online booked appointments at assessment centres should begin by Tuesday, October 6 if not already in place," the ministry said.

As of Oct. 6, residents who have symptoms of COVID-19 must call into one of the province’s 153 assessment centres and speak to a nurse practitioner before making an appointment. Some assessment centres also allow for online booking.

About 50 pharmacies are also offering COVID-19 tests by appointment for priority groups. Residents who are asymptomatic and have not been in contact with someone who has tested positive for the disease will be allowed to get a test at one of those locations.

The province has said they will be adding more pharmacies to the list "based on the impact of this program," but little information has been provided yet regarding their location.

Ontario’s COVID-19 processing backlog hit an all-time high on Friday, with 90,513 test samples still under investigation. As of Monday, that number has decreased to 68,006.

A little more than 38,000 tests were conducted in the last 24-hour period. The province has said it hopes to reach 50,000 tests in mid-October and 68,000 in mid-November.

What does the wait time look like?

Those trying to make an appointment for a COVID-19 test may have to wait a few days once the systems become active.

On Monday, some of the largest assessment centres at hospitals in the Greater Toronto Area were reporting no availabilities until at least Thursday.

Some of the centres are also only providing two days-worth of appointments, specifying that timeslots will become available 48 hours in advance.

Infectious Disease Specialist Dr. Isaac Bogoch said that while an appointment-based system may have drawbacks, it also may help in more effective testing.

“We know that a system like this can really ensure that people who have symptoms or exposures or risk factors are prioritized for a test. We also know that this will help with the lineups and we'll help with the tremendous backlog,” Bogoch said.

“There's obvious drawbacks as well. This creates another barrier to getting a diagnostic test and certainly many people that might really truly need it might be dissuaded from getting a test because of this system.

What does this mean for children who need to be tested?

The long lineups at assessment centres began to appear in early September as schools reopened across Ontario.

As students returned to class, parents and teachers were told that children exhibiting any of the 17 symptoms listed in its screen questionnaire would have to self-isolate at home for 14 days or test negative for COVID-19 before coming back to school.

Symptoms listed in this questionnaire included a cough, runny nose, and headaches.

In October, the provincial government altered that list so that children with a runny nose or sore throat do not have to get a COVID-19 test in order to return to class.

Instead, they just have to stay home for at least 24 hours in order to monitor those symptoms.