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Long COVID: What do we know?

Thursday, April 1, 2021

Canadian flagship initiatives like CanCOGeN’s HostSeq initiative – which will sequence the genomes of up to 10,000 patients diagnosed with COVID-19 – will provide key insights into long term effects and management of this debilitating disease.

As the fight continues to reduce the number of new COVID-19 cases, health professionals and researchers are also exploring the long-term effects of this debilitating disease and why some people experience symptoms for a longer period than others. Multiple studies show that factors specific to the individuals who contract COVID-19 (the “hosts”) are among the leading variables affecting how the disease manifests itself – from no symptoms to mild discomfort to severe illness or death. The term “Long COVID” has been coined to describe the experience of those who suffer COVID-19 symptoms over a prolonged period.

What do we know about Long COVID?

Researchers at King’s College London, found that Long Covid affects around 10 per cent of 18-to-49-year-old COVID-19 sufferers, with that percentage rising to 22 per cent for those over 70. While there are no defined symptoms associated with Long Covid, sufferers most commonly experience extreme fatigue long after other clinically defined symptoms have been cleared. Other symptoms include breathlessness, persistent cough, body/muscle aches and pains, headaches, as well as long term damage to the heart, lungs and kidneys. The British Society for Immunology provides an excellent summary of what we do and don’t currently know about the immunological health consequences of Long Covid.

Do we know what causes this manifestation of COVID-19?

There are several theories on the causes of Long COVID. One is that SARS-CoV-2 might be lingering in the body at levels below detection. Another is that since SARS-CoV-2 can infect a wide variety of cells in the body, it has the potential to trigger an overactive immune response, which also causes damage throughout the body. From what we know so far, the key to how each person responds to COVID-19 in the long term may also be in our genes. A recent study from U.K. finds variants of five key genes responsible for symptoms associated with COVID-19. These and other genes could also be involved in long-term affects of COVID-19.

What’s next in the fight to tackle Long COVID?

For a better understanding of Long Covid, future studies will need to focus on identifying “genetic markers” for it. Genomics can play a crucial role in helping with early identification and treatment of patients at risk for Long Covid. Canadian flagship initiatives like CanCOGeN’s HostSeq initiative – which will sequence the genomes of up to 10,000 patients diagnosed with COVID-19 – will provide key insights into long term effects and management of this debilitating disease.


The Canadian COVID-19 Genomics Network (CanCOGeN) is on a mission to respond to COVID-19 by generating accessible and usable data from viral and host genomes to inform public health and policy decisions, and guide treatment and vaccine development. This pan-Canadian consortium is led by Genome Canada, in partnership with six regional Genome Centres, the National Microbiology Lab and provincial public health labs, genome sequencing centres (through CGEn), hospitals, academia and industry across the country.