Just as Australia starts to breathe a sigh of relief over coronavirus cases, researchers say we need to be prepared for a frightening "silent wave".
Hidden behind the current worldwide Covid-19 pandemic is another potential pandemic few comprehend.
As scientists are still learning about how the coronavirus invades the brain and the long-term neurological consequences that poses, some fear we're headed for a "silent" third wave, this time combined with Parkinson's disease.
In a research paper published today, experts pose the question: Parkinsonism as a Third Wave of the Covid-19 Pandemic?
It comes as cases of Parkinson's disease are set to double in the next 20 years, even before the potential Covid-19 effects.
"We're living through two pandemics," Professor Kevin Barnham, from Australia's Florey Institute of Neuroscience and Mental Health, said.
"We are talking about an insidious disease affecting 80,000 people in Australia, which is set to double by 2040 before even considering the potential consequences of Covid, and we currently have no available disease modifying therapies.
"It is very worrying indeed to consider the potential global increase of neurological diseases that could unfold down the track."
Researchers are calling for urgent action to be taken to have more accurate diagnostic tools available to identify neurodegeneration early, and a long-term monitoring approach for people who have recovered from the SARS-CoV-2 virus.
Inspired by Australia's National Bowel Cancer Screening Programme, they hope to set up a national screening program for Parkinson's to get to the disease early.
THE 'REALLY CONCERNING' IMPACT OF COVID-19
Florey researcher Leah Beauchamp said there was increasing evidence the SARS-CoV-2 virus was getting into the brain, although its entry mechanism was unclear.
She said when it first emerged that one of the symptoms of the virus was a loss of smell, her interest was piqued.
Beauchamp said while a loss of smell might seem minor, it was an indicator of inflammation, which was a major "red flag".
"Inflammation in the brain greatly increases the risk of neurodegenerative diseases, including Parkinson's disease," she said.
"We believe that loss of smell presents a new way forward in detecting someone's risk of
developing Parkinson's disease early. Armed with the knowledge that loss of smell presents in around 90 per cent of people in the early stages of Parkinson's disease and a decade ahead of motor symptoms, we feel we are on the right track."
Beauchamp said neurological symptoms were also associated with the Spanish flu 100 years ago and five years later, three was a two to three-fold increase in the incidence of Parkinson's worldwide.
"This is really concerning to us given 30 million people have been infected with COVID-19 worldwide.
"We're concerned about the implications this will have on the Parkinson's pandemic."
Beauchamp said while the world wasn't prepared 100 years ago, we could take action this time to avoid history repeating itself.
SILENT SYMPTOMS CAN HIT EARLY
Barnham said although Parkinson's was usually associated with the ageing and elderly, the disease most likely started in middle age.
"We have to shift community thinking that Parkinson's is not a disease of old age. As we've been hearing time and time again, the coronavirus does not discriminate – and neither does Parkinson's."
Clinical diagnosis of Parkinson's disease currently relies on presentation of motor dysfunction, but research shows that by this time 50-70 per cent of dopamine cell loss in the brain has already occurred.
Barnham said neurodegeneration started 10 to 20 years before the movement disorder, creating a challenge and an opportunity.
The challenge is there are little to no symptoms but the opportunity is early intervention could prevent onset.
Minor symptoms include loss of smell, sleep disorder, anxiety, depression and constipation.
"Any one of those on their own are no big deal but collectively they paint a picture of a diseased state," he said.
"It's the ideal time to intervene with treatments. By waiting until this stage of Parkinson's disease to diagnose and treat, you've already missed the window for neuroprotective therapies to have their intended effect."
Barnham said while a screening programme would require serious investment - he estimated $5-10 million over five years - the annual cost of Parkinson's disease to Australia is more than $10 billion.
"It doesn't sound like a bad investment to me."
They plan to put the proposal forward for funding from the Australian Government's Medical Research Future Funding scheme.