The monkeypox virus causes monkeypox disease. This monkeypox virus is of the same family of viruses as the variola virus, responsible for smallpox. Monkeypox symptoms are very similar to that of smallpox but milder. Monkeypox is a rare disease and not fatal and it is not related to chickenpox. The monkeypox symptoms are similar to smallpox symptoms, only milder, and it is rarely fatal. The incubation period is approximately 1 to 2 weeks. Monkeypox Symptoms include rash, fever, headaches etc.