TORONTO -- At COVID-19 assessment centres across the GTA hundreds of patients are showing up with possible symptoms of the virus.

Five assessment centres have opened as of Friday that are dedicated to COVID-19 testing in the Greater Toronto Area, and the province is promising that more will be established as the outbreak grows.

Here’s what you need to know before you go to one of the assessment centres.

Michael Garron Hospital

Michael Garron Hospital’s centre opened on Thursday. Anyone hoping to be tested at this location must book an appointment. It’s not open for walk-ins.

When patients arrive, the hospital said they will be screened, then assessed by a doctor or a nurse. Based on that assessment, the patient may get tested.

The hospital said on Thursday that 45 patients met the criteria and had a COVID-19 test.

THREAD: We opened a #COVID19 Assessment Centre on-site (825 Coxwell Ave.) in an isolated clinic with a designated entrance at Mortimer avenue, west of the ED. The Centre is open daily from 12-8 pm by appointment only. Learn more about how it works: https://t.co/CqUzPBDhDz pic.twitter.com/oE2zvh45xh — MGH / TEHN (@MGHToronto) March 13, 2020

On Friday, not everyone who spoke with CTV News Toronto was able to get an appointment.

Natalie Kovacs returned from New York on Thursday night and ended up going to the emergency room to be seen.

“I’m tired and I have a cold, but I think I’m fine. I’m just doing it as a precaution. Otherwise I’m not allowed to see my mom at the retirement home,” Kovacs said.

A spokesperson for the hospital said that call volumes are “extremely high” and people are encouraged to keep trying if they can’t get through.

Instead of going to the emergency room, Ontario’s Ministry of Health says that the person should stay at home and keep trying to make another appointment.

North York General Hospital

At North York General Hospital’s assessment centre, patients don’t need an appointment.

Dr. Paul Hannam, Chief of Emergency Medicine, said that when patients show up, they will go through the emergency doors and turn left into a different area, where they are kept away from patients with non-COVID-19 concerns.

“If you have chest pain or a broken ankle we can direct you to a separate area. It’s completely separate. You’re not in contact,” Hannam said.

At the centre, Hannam said possible coronavirus patients will be seen by a triage nurse and, if appropriate, by another nurse and doctor.

Hannam said that after opening Wednesday night, the hospital saw 200 people in the first 24 hours.

He expects the centre to stay open between four and six weeks.

Mississauga Hospital and Credit Valley Hospital

Trillium Health Partners opened assessment centres at Mississauga Hospital and Credit Valley Hospital.

“To protect our most vulnerable patients, the assessment centres are located adjacent to our main hospital sites,” said spokesperson Keeley Rogers in an email to CTV News Toronto.

She said the centres are open from 9:30 a.m. to 9:30 p.m., but they are not considered walk-in clinics. At this time they will only accept patients with referrals from the emergency department and Peel Public Health.

As part of our continued efforts to reduce the spread of infection to our sickest patients, improve flow in the ED & enhance capacity across sites, THP has opened a #COVID19 Assessment Centre at the Mississauga Hospital & Credit Valley Hospital. ⬇️ More: https://t.co/qd9tRCOLn6 pic.twitter.com/FrZs0Z0JXY — Trillium Health Partners (@THP_hospital) March 13, 2020

“Patients seen at the assessment centre will be assessed by answering questions about their symptoms, travel history or exposure to known positive cases of COVID-19,” Rogers said.

“Only patients that meet certain criteria will be tested for COVID-19. Peel Public Health will follow up with patients who are diagnosed with COVID-19.”

People wondering if they should visit an assessment centre is encouraged to contact Peel Public Health at 905-799-7700.

Mackenzie Health’s Medical Urgent Care Clinic

Mackenzie Health tells CTV News Toronto that it’s activating an assessment centre Monday evening.

“Assessments will be done by appointment,” said spokesperson Christina Cindric in an email..

She said it has a separate entrance and is close enough to the emergency department in case someone being assessed requires urgent care.

“We want to remind our community that if someone is concerned about their symptoms or are worried about potential exposure to COVID-19, they should connect with Telehealth Ontario.”

More COVID-19 assessment centres coming

The Ministry of Health said additional assessment centres will be established across the province in the coming weeks.

“These centres are located in dedicated spaces that will facilitate high-quality care, to protect broader patient populations. Regions without an assessment centre will continue to be serviced by their local hospitals or primary care settings,” a spokesperson said.