There is an argument for it that continuing to work and therefore exposing yourself to stress will make the recovery time longer. Also, that if you place the expectation on employees to work while at home they will feel obligated to even if what they really need is bed rest.

Personally I feel managers should be allowed to use some discretion. If staff look to me like they’re coming down with something but maintain they are ok to work I will always ask if there’s any work they can take home with them, just on the off chance that they are getting sick and could infect others. If they tell me they are feeling ill or I can see they are really in need of rest then I will explicitly tell them not to log on and will challenge them if they do. Unsurprisingly my team sickness rates are better than on teams where the managers try and push their staff when they clearly aren’t well. It’s better for morale and productivity also.