Long COVID is the common term for “post-acute sequelae SARS-CoV-2 infection” (PASC). It applies to the roughly 20% of people who experience lingering symptoms for weeks, months and occasionally even years after recovering from a COVID infection. The risk is higher for older patients, especially those who needed hospitalization, but often arises in otherwise healthy young people, even those whose initial symptoms were mild or moderate. While vaccination appears to provide some protection, there is evidence that the risk rises with successive COVID bouts.

COVID is so new that it has taken time for researchers to zero in on potential causes, especially since symptoms vary so widely in different people. That should perhaps have been a clue because other long-puzzling conditions characterized by a similar variety of symptoms following viral infections have turned out to be neuro-immune disorders. Long COVID now has its own official diagnostic code, which will improve tracking.

The most common symptoms (listed in decreasing order of severity) are:

  • Fatigue/weakness
  • General pain/discomfort
  • Affected sleep
  • Breathlessness
  • Impaired usual activity
  • Impaired memory
  • Exertional breathlessness
  • Poor concentration
  • Cognitive dysfunction
  • PTSD
  • Impaired walking/mobility
  • Joint pain
  • Anxiety
  • Depression

Omicron primarily infects the human upper respiratory tract. As illustrated above, neurons in the brain’s olfactory bulb project into our nasal cavity linings, providing the virus with a direct pathway into our brains and thereby bypassing the normally protective blood-brain barrier. Once there, it can disrupt blood vessels, allowing the escape of activated immune cells such as macrophages which cause inflammation and kill nearby neurons. The virus can also infect astrocytes, which are crucial neural support cells.

Actual symptoms vary according to which brain areas happen to be most impacted. The very common brain fog and disruption to memory and concentration may be attributable to the close connection between the olfactory bulb and the hippocampus. Impacts on brain cells comprising that autonomic nervous system could explain symptoms such as chronic fatigue, rapid heartbeat and shortness of breath. As for the duration of those symptoms, one study found COVID genetic material in a patient’s brain almost eight months after the initial infection.

This update summarizes an excellent article entitled The Brain and Long COVID from the March 2023 issue of Scientific American. While we can’t share it with you due to copyright restrictions, those who are interested can buy it (~$12) at their nearest newsstand. As reported in the article, treatments are currently being explored by multidisciplinary medical and research team but, for the foreseeable future, it is hard to imagine that level of care becoming available to the vast majority of Long COVID sufferers.

There is some evidence that taking antiviral medications such as Paxlovid within the first few days of a COVID infection can modestly (~25%) reduce the risk of most Long COVID symptoms, though that may not necessarily apply to the most recent variants. Overall, common-sense precautions to minimize one’s risk of infection/reinfection remain the most rational approach for most Canadians and their families.