Early signs of Monkey-pox. disease include flu-like symptoms such as rashes, fever, chills, headache, muscle aches, fatigue. These are common but after a few days, a rash often develops. The rash starts as flat, red bumps which can be painful, which later turn into blisters (fills with pus). Those blisters crust over and fall off - the whole process can last two-four weeks.