Cold, Flu or COVID-19? Symptoms and When to Come In
All three can start the same way — a scratchy throat, a bit of fatigue, maybe a cough. The symptoms alone often aren't enough to tell them apart. Here's how to read the signs, the specific warning signs that mean go straight to the ER, and when to call Ontario's free health line instead of guessing.
Quick answer
A cold usually stays mild and in the upper airways — runny nose, sneezing, sore throat, rarely a fever. The flu tends to hit fast (1–4 days after exposure) with fever, cough and body aches. COVID-19 can look like either, sometimes with a new loss of taste or smell. Most cases of all three are managed with rest and fluids at home. Call 811 (Health811) if you're unsure what to do next. Call 911 or go to the nearest ER for trouble breathing, chest pain, confusion, trouble staying awake, or blue/grey/pale skin. Sources: canada.ca.
How to tell them apart
It's genuinely hard to self-diagnose — the same virus can look different in different people. This is a general guide, not a diagnosis (canada.ca):
| Common cold | Flu | COVID-19 | |
|---|---|---|---|
| Onset | Gradual, over a day or two | Sudden — 1 to 4 days after exposure | Can be either, 1–14 days after exposure |
| Fever | Uncommon | Common, often high | Common |
| Cough | Mild | Common, can be severe | New or worsening cough |
| Body aches | Mild or none | Common, often severe | Common |
| Other | Runny/stuffy nose, sneezing, sore throat | Chills, headache, fatigue | Sometimes new loss of taste/smell, shortness of breath |
Source: canada.ca (COVID-19 symptoms & treatment; seasonal flu symptoms). This guide is general information, not medical advice — testing or a clinical assessment is the only reliable way to know for sure.
Go to the ER or call 911 for these signs
These are the specific warning signs that mean don't wait — go straight to the nearest emergency department or call 911 (canada.ca):
- Trouble breathing or severe shortness of breath
- Persistent chest pain or pressure
- New onset confusion
- Difficulty waking up or staying awake
- Pale, grey or blue-coloured skin, lips or nail beds
These apply to adults. Parents of a sick child should also seek immediate care for unresponsiveness or refusal to eat or drink.
Not sure? Call Health811 before you decide
Health811 is Ontario's free 24/7 health line — call 811 or use the online chat. A registered nurse helps you figure out the right next step: rest at home, book a doctor's visit, come in to a walk-in clinic, or go to the emergency department. It's the right call when you're not sure how serious things are and don't want to guess. It's not for emergencies — if you have any of the warning signs above, skip 811 and go straight to the ER or call 911.
Practical steps this season
- Rest and fluids first — most colds, and many flu and COVID-19 cases, resolve with home care.
- Watch for the warning signs above, not just how you feel in general.
- If you're at higher risk (65+, pregnant, young children, underlying conditions), don't wait as long to get assessed.
- Call 811 if you're unsure, call 911 for the warning signs — never the other way around.
- Save the clinic's number — (905) 848-4844 — for a same-day walk-in visit.
Frequently asked questions
How can I tell if I have a cold, the flu, or COVID-19?
It's genuinely hard by symptoms alone. A cold usually stays in the upper airways with rare fever; the flu comes on fast with fever, cough and aches; COVID-19 can look like either, sometimes with a new loss of taste or smell. Testing or a clinical assessment is the only reliable way to know for sure. Source: canada.ca.
What are the emergency warning signs for COVID-19?
Trouble breathing or severe shortness of breath, persistent chest pain or pressure, new onset confusion, difficulty waking up or staying awake, or pale, grey or blue-coloured skin, lips or nail beds — call 911 or go to the ER immediately. Source: canada.ca.
When should I call Health811 instead of going straight to a clinic?
When you're unsure how serious your symptoms are and want help deciding — not for emergencies, which go straight to 911 or the ER.
How quickly do flu symptoms appear after exposure?
Generally 1 to 4 days — faster and more sudden than a typical cold. Source: canada.ca.
Does Medicare Clinic see walk-in patients for cold, flu or COVID-19 symptoms?
Yes. Medicare Clinic's walk-in clinic near Square One sees same-day sick visits, with an on-site lab and pharmacy for testing and prescriptions in one trip. Call ahead if you're not sure whether to come in.