Forgive me for asking what should be a really obvious question, but I'm not sure I completely understand this, and I want to. Some people say that ME/CFS is the only disease with post-exertional malaise. Shall I interpret this to mean that people with bad flu don't experience malaise, profound exhaustion, and worsening of symptoms upon physical or mental exertion? And people with chronic untreated Lyme (I don't know what the correct term is) don't? People with FM, atypical MS, or non-HIV AIDS (I don't actually know what this is -- is it ME/CFS?) don't? People with Lupus and Behcet's and CHF can exert themselves without payback? What is it like for those, then? Just kind of hard to do stuff but it doesn't affect other symptoms and you don't need to recover afterward? But surely exertion requires rest afterward? When people tell people with the flu to get some rest, what are they saying? That you're OK if you don't rest, but it's better for the immune system to rest? Maybe I have been sick for far too many decades to remember any other disease experience. Maybe somebody can clarify this. Thanks.