Almost 10 weeks into the pandemic, COVID-19 is continuing to surprise and baffle health experts.

In fact, experts’ picture of exactly how COVID-19 might play out in the body is now quite different to what was thought as little as a few weeks ago, with some experts saying it could be better described as three different diseases.

We have known for a while that the mild to moderate form of the disease — a flu-like illness with fever, muscle aches and respiratory symptoms, or often no symptoms at all — is almost like “child’s play” compared to the major damage to organs like the the lungs, heart, brain, and kidneys seen when COVID-19 becomes severe.

Umesh Gidwani, head of cardiac intensive care at New York’s Mount Sinai Hospital, says that trying to treat the severe form of the disease is like facing a terrifying fire, burning out of control.

“The patients we take care of [in intensive care] are those in whom the fire has already destroyed the house. But there continues to be embers and small fires. I can’t enter the house because it’s too hot and things are falling on me,” he says.

“[Severe disease] is almost a completely different animal [compared] to someone who is recovering at home with some chicken soup and paracetamol”.

And now it seems there is evidence of a third variation in illness that can occur following exposure to the virus — a mysterious new disease given the name paediatric multisystem inflammatory syndrome, with an entirely different set of symptoms again.

The syndrome seems to only affect children, unlike both mild and severe COVID-19, which mostly affect adults. However the link between the inflammatory syndrome and the virus that causes COVID-19 is not yet 100 per cent confirmed.

The bottom line, says Dr Gidwani, is what we have been calling a single disease — COVID-19 — is really looking more like three separate diseases.

He and others draw this conclusion based on how the virus affects the immune system.

“The key disaster is the extent and severity of the immune response,” he says.

It is now clear the symptoms experienced by people with severe COVID-19 are largely caused by the body’s disordered immune response to the virus rather than the virus itself, Dr Gidwani says.

In fact, the disordered immune response in severe COVID-19 is the disease; they are one and the same thing.

Image Credit: Umesh Gidwani