[user104658]

He has potentially hindered his recovery by staying in charge of government... I was reading earlier about the links between sleep, adrenaline and fever. Basically when you have a fever, it tends to "break" when you're in a relaxed deep-sleep state and the process is held back by high adrenaline levels. Essentially if you don't let yourself relax when you're ill, the fever can fail to break, your immune system doesn't operate anywhere near full capacity, and that massively increases the risk of developing a secondary infection (like pneumonia). That's why they start to be concerned when people's temp is still up at 7 days. Ideally, if your immune system is doing its job, it should be down within 3 - 5 days.

Basically the stress and probably sleep deprivation that comes with being PM may well be part of what's stopped him from making a timely recovery.