The first known case of MonkeyPox virus was in 1958 when a pox like diseases was detected in monkeys that were kept at a research center in Denmark. First ever known case of MonkeyPox was in 1970 in Democratic Republic of Congo during small pox surveillance. The first know patient was 9 months old baby with signs of fever and rash like symptoms over the infected baby.
The rashes developed into haemorrhagic lesions all over the body and healed with 2 weeks. The 9 month old baby succumbed to secondary infections despite recovering from MonkeyPox. Till 2022, MonkeyPox cases was mostly discovered in DRC (Democratic Republic of Congo), Liberia, Sierra Leone, Nigeria and Ivory Coast.
All the cases discovered in the above countries had a 11% fatality rate and this fatality rate is only for those who didn’t receive a smallpox vaccination which indicates that vaccination against smallpox might be effective in preventing MonkeyPox. The fatality rate was highest among children under 4 years of age and these cases also occurred in other African countries like Benin, Cameroon, Gabon, Ghana, SierraLone and South Sudan. The first reported case of MonkeyPox outside of Africa was in United States. More details about Monkey Pox could be found here
Source: https://www.mdpi.com/1422-0067/23/14/7866