After healing, the lesions may leave pale marks before becoming dark scars.An unwell person may remain so for two to four weeks. Complications
Complications include secondary infections, pneumonia, sepsis, encephalitis, and loss of vision with severe eye infection. If infection occurs during pregnancy, still birth or birth defects may occur. The disease may be milder in people vaccinated against smallpox in childhood. Patel and colleagues, in the BMJ, demonstrate that this virus can produce severe symptoms, particularly in HIV-positive people. The  descriptive case series reveal that symptoms can be so severe that hospitalization is required in 10% of cases. The study also shows that 75% of patients (15 out of 20 participants) admitted to the hospital were HIV-positive individuals. Overall, the study depict a new variety of clinical manifestations including proctitis and rectal perforation. The pictures of genital lesions published in the BMJ show the severity of monkeypox, which is often described as causing moderate symptoms. In other animals
The disease has also been reported in dormice, tree squirrels, rope squirrels and non human primates. Rodents such as rats and mice are likely susceptible but not known. Signs and symptoms in animals vary among different species. Monkeypox infected Gambian pouched rats may have mild symptoms. During the 2003 US outbreak, affected prairie dogs presented with fever, cough, sore eyes, poor feeding and rash. Non-human primates present similarly. They may have breathing problems, facial swelling, mouth ulcers and swollen glands. In cynomolgus monkeys, the time from exposure to symptoms was noted to be around a week.
The first documented cases in humans was in 1970, in six unvaccinated children during the smallpox eradication efforts; the first being a 9-month old boy in the Democratic Republic of the Congo (formerly Zaire). The others, including three who were playmates, were in Liberia and Sierra Leone. It was noted to be less easily transmissible than smallpox. From 1981 to 1986, over 300 cases of human monkeypox were reported in the DRC, the majority being due to contact with animals. In 1996, the disease reemerged in the DRC with 88% of cases resulting from human-to-human transmission. Small viral outbreaks with a death rate in the range of 10% and a secondary human-to-human infection rate of about the same amount occur routinely in equatorial Central and West Africa. In humans, the disease remained confined to the rain forests of Western and Central Africa until 2003, when an outbreak of monkeypox occurred in the US. All cases were traced to sick rodents imported from Ghana. Local prairie dogs caught the infection and passed it onto their owners. The disease was found to be mild and there were no deaths. Between 1970 and 2019 the disease was reported in 10 African countries; mostly in Central and West Africa.In 2018, cases of monkeypox were diagnosed in the UK in two unrelated travellers from Nigeria. That year the first human-to-human transmission outside of Africa was confirmed in the UK. This person was a healthcare worker who possibly contracted the disease from contaminated bedlinen.