The silent third wave of Covid-19 might be Parkinson's

  • A wave of Parkinsonism conditions could be the future in a post-Covid world.
  • The hypothesis explores neurological symptoms caused by the coronavirus.
  • Neuroinflammation is a major link between viral infection and Parkinson's disease.

The neurological effects of Covid-19 have been well documented, but some scientists are raising concerns about its potential influence on the future development of neurological conditions like Parkinson's disease.

This hypothesis was explored in a recent paper published in the Journal of Parkinson's Disease, where researchers theorised that Covid-19's neurological symptoms could be a precursor to diseases like Parkinson's.

For example, the coronavirus symptom of losing one's sense of taste and smell also appears in Parkinson's and Alzheimer's. This symptom is probably underestimated due to a reliance on self-reporting from patients.

It could mark a "third wave" of the pandemic that healthcare systems around the world should prepare for.

READ | To what extent is Covid-19 damaging the brain? 

Missed chance to study 1918 pandemic

Scientists missed the opportunity to study neurological phenomena during the time of the 1918 Spanish Flu pandemic, where patients presented with encephalitis lethargica – a disease that attacks the brain and causes a zombie-like state.

In the 1920s there was a rise in other similar Parkinsonism conditions, which is any condition that causes tremors, impairs speech and limits movement due to the loss of dopamine-containing brain cells. This happened again in the 1940s. 

"While the acute effect of the virus on the nervous system function is vastly overshadowed by the respiratory effects, we propose that it will be important to monitor convalescent individuals for potential long-term implications that may include neurodegenerative sequela, such as viral-associated Parkinsonism," wrote the researchers.

"As it is possible to identify premorbid harbingers of Parkinson's disease, we propose long-term screening of SARS-CoV-2 cases post recovery for these expressions of neurodegenerative disease."

READ MORE | We've been here before: lessons from the 1918 Spanish flu pandemic

How can Covid-19 lead to Parkinson's?

The disease is believed to be caused by chronic neuroinflammation, which in turn leads to degeneration in the brain. However, scientists aren't sure if it's, in fact, happening the other way around. There are also theories that the inflammation may be caused by bacteria endotoxins in the gut and mouth. 

These endotoxins may cause cytokine storms – just like SARS-CoV-2 infection, which can also cause neuroinflammation.

The evidence of a pathogen causing Parkinson's is inconclusive, but a pathogen might weaken the system to make it easier for the disease to take hold.

Waiting game

The data is still sparse, but the hypothesis does raise some very serious questions about a post-pandemic world. It also pokes holes in the herd immunity concept as it requires a high infection rate. The symptoms might be mild, but might cause serious unknown health issues further down the line.

"It remains to be seen whether Covid-19 viral infections will be later linked to Parkinsonism, as is the case in other viruses. Also, unlike many neurological conditions, such as neuropathy, there are emerging tools available to identify Parkinsonism early in the disease process.

"As such, this review serves as a 'call to arms' for the neurology community in preparation of a potential wave of Parkinsonism to come," warned the writers. 

READ | Why check-ups for Covid-19 recoveries are important

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