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.
On 23 July 2022, the World Health Organization (WHO) declared the outbreak a Public Health Emergency of International Concern (PHEIC) with more than 53,000 reported cases in 75 countries and territories. Signs and symptoms
It is possible for a person to be infected with monkeypox without showing any symptoms. Monkeypox symptoms tend to begin 5 to 21 days after infection, with early symptoms including headache, muscle pains, fever and fatigue, initially resembling influenza. Within a few days of the fever, lesions characteristically appear on the face before appearing on the trunk then elsewhere such as palms of the hands and soles of the feet. The disease can resemble chickenpox, measles and smallpox but is distinguished by the presence of swollen glands which may appear behind the ear, below the jaw, in the neck or in the groin, before the onset of the rash. Many cases in the 2022 monkeypox outbreak presented with genital and peri-anal lesions, fever, swollen lymph nodes, and pain when swallowing, with  some patients manifesting only single sores from the disease.Three-quarters of affected people have lesions on the palms and soles, more than two-thirds in the mouth, a third on the genitals and one in five have lesions in the eyes. They begin as small flat spots, before becoming small bumps which then fill with at first clear fluid and then yellow fluid, which subsequently burst and scab over, persisting for around ten days. There may be a few lesions or several thousand, sometimes merging to produce large lesions.