The new coronavirus can also push the immune system into overdrive, unleashing an indiscriminate assault — known as a cytokine storm — on pathogens and their human hosts alike.
“Most viruses can cause disease in two ways,” explained Jeremy Rossman, a senior lecturer in virology at the University of Kent.
“They can damage tissue where the virus replicates, or they can cause damage as a side-effect of the immune system fighting off the disease.”
Doctors suspect, for example, that COVID-19 is behind the hospitalisation in recent weeks of several dozen children in New York, London and Paris diagnosed with a rare inflammatory disorder similar to toxic shock syndrome.
Affecting mainly young children, the painful disease attacks artery walls and can cause organ failure.
Dozens of medical studies in recent weeks have detailed other potentially lethal impacts including strokes and heart damage.
Researchers from the urology department of Nanjing Medical University, writing this week in Nature Reviews, described patients developing severe urinary complications and acute kidney injury.
They also observed “dramatic changes” in male sex hormones.
‘1-in-10,000 still a lot’
“After recovery from COVID-19, young men who are interested in having children should receive a consultation regarding their fertility,” they concluded.
Does that mean that COVID-19 causes a uniquely broad array of symptoms? Not necessarily, virologists and other experts say.
“If it is a common disease, then even rare complications will happen frequently,” Babak Javid, a consultant in infectious diseases at Cambridge University Hospitals said.
There are nearly 3.8 million confirmed COVID-19 cases around the world, but the true number of infections — taking into account undetected and asymptomatic infection — “is going to be in the tens, possibly hundreds of millions,” he said.
“So if one-in-1,000, or even one-in-10,000, get complications, that is still thousands of people.”
Some of the rarer symptoms associated with COVID-19 are also known to have been triggered by influenza, which kills several hundred thousand people worldwide every year, he noted.
For the new coronavirus, frontline general practitioners across the globe have been the first to look for patterns in the unfolding pandemic.
“At the outset, we were told to watch out for headaches, fever and a light cough,” recalls Sylvie Monnoye, a family doctor in central Paris for nearly three decades.
“Then they added a runny nose and a scratchy throat. After that, digestive problems, including stomach aches and severe diarrhoea.”
The list kept growing: skin lesions, neurological problems, sharp chest pains, loss of taste and smell.