I can verify. I had both the original Covid a year ago and then the/a milder mutant strain November. I survived Covid but felt unusual pains in chest (not from coughing). Felt like low oxygen but no direct reading of that. EKG showed odd waveform change. But uncertain direct cause - could have been muscle or nerve damage or even clot; I went on a blood thinner but it had no effect. I have recovered now but it was a real mystery what was going on.