Until March this year, Felicity Callard was fit, active and strong.
Then the 49-year-old British university professor caught COVID-19. Initially, she was sick for two weeks, then seemed to get better.
"I felt a lot better and thought okay, it's been terrible, but I'm getting better and then everything actually got much worse in the second month. So I ended up at A&E in the second month was just incredible abdominal pains and lots and lots of joint pains and terrible headaches, sort of shooting pains up and down my arms and then that's kind of come and gone and it's now, you know, over five and a half months later and I still feel really pretty unwell, both physically and cognitively."
This patient has, for now at least, recovered.
But Callard is one of thousands of people dubbed "COVID long-haulers", or sufferers of what some call "long COVID".
Physical symptoms include breathlessness, memory loss, extreme fatigue and muscle pain, but for many, the anxiety, depression and dread are at least as debilitating.
King's College London has devised a "long COVID" symptom tracker. Til Wykes is a psychology professor there:
"At the moment, we really don't have very much evidence of how many people develop long Covid and we don't know the range of problems that they have. We know that some people have reported breathlessness, some people have reported difficulties with their heart but also we we know that some people also have developed depression, maybe because they haven't been able to manage their symptoms or it could have been something totally separate."
Callard now sees the threat of COVID-19 everywhere; no longer controllable by hand-washing or social distancing.
"My life has shrunk basically to my house and, you know, a short distance away. So London has disappeared and my life as an academic has become very, very difficult to do because all the things I used to be able to do very easily are now a huge struggle."