After exposure, it may be several days to a few weeks before you develop symptoms. Early signs of mpox include flu-like symptoms, including: Fever. Chills. Headache. Muscle aches. Fatigue. Swollen lymph nodes. After a few days, a rash often develops. The rash starts as flat, red bumps, which can be painful. Those bumps turn into blisters, which fill with pus. Eventually, the blisters crust over and fall off — the whole process can last two weeks to four weeks. You can also get sores in your mouth, vagina or anus.