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COVID-19

COVID-19 is an infectious disease caused by the SARS-CoV-2 coronavirus.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 27, 2026|2 min read| Fact-checked

COVID-19 is an infectious disease caused by the SARS-CoV-2 coronavirus. It can cause mild to severe respiratory illness and other symptoms, and it continues to circulate globally as a public health concern. In Canada, public health agencies continue to track symptoms, variants, vaccination, and local transmission patterns.

Cause and transmission

COVID-19 is caused by the SARS-CoV-2 coronavirus. The disease spreads through infectious respiratory particles in the air from infected people.

Symptoms

Symptoms vary widely but commonly include fever, cough, tiredness, sore throat, shortness of breath, congestion or runny nose, headache, body aches, nausea, diarrhoea, and loss or change of taste or smell. Symptoms can change with new variants.

Course of illness

Symptoms typically appear within 5–6 days after infection, though they can take up to 14 days to develop. Many people recover within a few weeks, but some experience prolonged symptoms or more severe illness. Severe cases can require medical care.

Public health status

The World Health Organization states that COVID-19 continues to circulate globally and remains a significant public health concern, with hospitalizations and deaths still occurring.

Prevention and vaccination

Vaccines are available and help reduce the risk of severe disease, even though protection against infection can vary with time and emerging variants. Vaccination status can also affect how symptoms present.

Key facts

  • COVID-19 is caused by the SARS-CoV-2 virus.
  • Symptoms can range from mild illness to severe disease and may change with new variants.
  • Most people recover without treatment, but severe cases can require medical care.
  • COVID-19 continues to circulate globally and remains a significant public health concern.
  • People can be infected with COVID-19 more than once because immunity is not permanent.
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Canadian context

COVID-19 remains relevant in Canada because Canadian public health agencies continue to track symptoms, variants, vaccination, and local transmission patterns.

Frequently asked questions

What are the symptoms of COVID-19?
Common symptoms include fever or chills, cough, sore throat, tiredness, shortness of breath, congestion or runny nose, headache, body aches, nausea, diarrhoea, and loss or change of taste or smell.
How long does COVID-19 last?
Symptoms often improve within a few weeks for many people, but illness can last longer in some cases, especially after severe infection or with lingering symptoms.
Is COVID-19 still a pandemic?
COVID-19 is no longer described everywhere as an active pandemic, but WHO states it continues to circulate globally and remains a significant public health concern.
What is the latest COVID-19 variant?
The currently circulating variants change over time, and WHO and CDC note that symptoms can vary with new variants. For the latest named variant, public health agencies should be checked directly because it changes frequently.
How effective is the COVID-19 vaccine?
COVID-19 vaccines are effective at reducing severe illness, hospitalization, and death, but protection against infection can wane and vary by variant and vaccination status.
Can you get COVID-19 more than once?
Yes. Reinfection can happen, especially as immunity changes over time and new variants appear; prior infection does not guarantee permanent protection.

References

  1. Centers for Disease Control and Prevention — https://www.cdc.gov/covid/signs-symptoms/index.html
    Supports: Symptoms, timing of symptom onset, severity range, and variant-related symptom changes.
  2. NHS — https://www.nhs.uk/conditions/covid-19/covid-19-symptoms-and-what-to-do/
    Supports: Common symptoms and typical recovery timeframe.
  3. World Health Organization — https://www.who.int/news-room/fact-sheets/detail/coronavirus-disease-(covid-19)
    Supports: Cause, common symptoms, ongoing global circulation, and public health significance.
  4. World Health Organization — https://www.who.int/health-topics/coronavirus
    Supports: Symptoms, incubation period, and serious symptoms.