The description of the blue slaad's claw attack (MM, page 276) says:
While infected, the target can’t regain hit points, and its hit point maximum is reduced by 10 (3d6) every 24 hours. If the disease reduces the target’s hit point maximum to 0, the target instantly transforms into a red slaad or, if it has the ability to cast spells of 3rd level or higher, a green slaad. Only a wish spell can reverse the transformation.
This is in reference to the Blue Slaad's claw attack. The final sentence in the quote is that only a wish spell can reverse the transformation, but nothing is stated about recovering their HP. If the disease is cured before the target is transformed, do they regain their lost HP?
In addition, is the first HP loss after 24 hours or immediately?