COVID-19 can wreak havoc on your body. So will it cause health issues decades down the road?

The illness once dubbed a "pneumonia of unknown cause" in the early days of 2020 has revealed itself to be something far more strange.

Two years into this pandemic, we now know COVID-19 can lead to a dizzying array of symptoms — from heart inflammation to brain fog to the loss of sense of smell or taste. Some people's toes turn red; others go on to develop diabetes. SARS-CoV-2 also impacts various organs and sometimes causes long-lasting breathing problems, fatigue or chronic kidney impairment.

Time and research have shown that the virus has quite a knack for wreaking havoc on the human body under the right conditions. So what will that mean for the long-term health of millions of people who've been infected — months, years or even decades down the road?

"There are some 'known' unknowns, like what will the rate and duration of long COVID be for different individuals," said Matthew Miller, an associate professor with McMaster University's Immunology Research Centre in Hamilton.

"And then there are 'unknown' unknowns, like what might happen 30 or 50 years from now."

SARS-CoV-2's ability to spread throughout the body is largely tied to the spike proteins on its surface, which bind to ACE2 — a protein on the surface of various types of human cells — like a key into a lock.

That means the virus can reach far beyond the respiratory tract, causing inflammation wherever it spreads.

"We've already shown this virus, even in the acute stage, does have impact on the brain and on our central organs like the heart, and pancreas and areas where other viral infections have caused longer-term inflammatory changes that have led to chronic disease," said Dr. Cory Neudorf, the public health, health systems and social policy impacts pillar co-lead for CoVaRR-Net, a team of Canadian researchers who banded together during the pandemic.

"I wouldn't be at all surprised if we see more chronic diseases due to COVID in the years to come."

SARS-CoV-2 infections have been linked to the onset of juvenile diabetes, for instance.

A January report from the U.S. Centers for Disease Control and Prevention showed that youth under the age of 18 were more likely to receive a new diabetes diagnosis a month or more post-infection than young people who didn't have COVID-19 — and when compared with respiratory infections before the pandemic.

"These findings are consistent with previous research demonstrating an association between SARS-CoV-2 infection and diabetes in adults," the report continued.

Other research has linked even mild cases of COVID-19 to long-term neurological symptoms. 

One recent U.S. study, which has not yet been peer-reviewed, involved autopsy results from nine patients and from lab mice that were purposely infected with SARS-CoV-2.