outbreak in 2022. “What We Know So Far” documents provide a rapid review of the evidence related to a specific aspect or emerging issue related to the 2022 worldwide monkeypox outbreak. Key Findings · Monkeypox is a viral zoonosis with typical incubation period of 6 to 13 days (range = 5 to 21 days). Person-to-person transmission of monkeypox occurs via close contact with lesions, body fluids, respiratory droplets and materials contaminated with monkeypox virus.1 · Sporadic monkeypox cases and outbreaks outside of endemic areas have been reported prior to 2022. · Genomic sequencing of a dozen cases from Germany, Portugal and Belgium suggests a single origin associated with the exportation of monkeypox virus from Nigeria to nonendemic countries (the UK, Israel and Singapore) in 2018 and 2019. · In May 2022, over 400 confirmed monkeypox cases with no direct travel links to monkeypox endemic areas were reported from over 20 countries, including Europe, the United Kingdom, Canada and the United States. · The epidemiological and clinical features of the 2022 outbreak in some European countries suggest human to human transmission via close contact, including close contact via sexual/intimate contact. Reported cases have mainly but not exclusively self-identified in men who have sex with men (MSM) seeking care in primary care and sexual health clinics. Potential factors contributing to this multi-jurisdictional surge in cases globally that have been proposed, or are being investigated, include: · Host/environment factors, e.g.: · Attendance at large-scale international events may have facilitated seeding of the monkeypox virus worldwide. · Lack of awareness of monkeypox among health care providers outside of endemic regions may have contributed to under-detection and subsequent low-level circulation of monkeypox. Multi-Jurisdictional Monkeypox Outbreak 2022 – What We Know So Far 2 · Lack of cross-protection from smallpox vaccination in younger populations as a result of the discontinuation of population-level immunization program following eradication of smallpox.1 · Agent factors, e.g.: · Potential for mutations leading to increased transmissibility: 50 single nucleotide polymorphisms in the 2022 outbreak virus have been detected compared to the monkeypox virus isolated in 2018 and 2019. · Available evidence suggests that those who are most at risk are those who have had close physical contact with someone with monkeypox while they are symptomatic. · Collaboration between human and veterinary public health is needed in view of the potential risk of human-to-animal transmission. It is beyond the scope of this document is to examine potential risk of human-to-animal transmission and endemic zoonotic monkeypox in Ontario. · The emerging epidemiology, and evidence concerning at risk population, routes of transmission, and disease severity need to be carefully monitored to inform public health response in Ontario. Background · Monkeypox is a zoonotic infection with symptoms similar to but less severe than those seen in smallpox patients.1 It is caused by monkeypox virus, an enveloped virus within the Orthopoxvirus genus in the Poxviridae family,2 first discovered in 1958 when outbreaks of a poxlike disease occurred in monkeys kept for research in a Danish laboratory.1 · Since the first identified human case in a child in the Democratic Republic of the Congo (DRC) in 1970,1 human monkeypox has been reported in a number of countries in Central and West Africa, in particular the DRC and Nigeria.3 Countries endemic for monkeypox are: Benin, Cameroon, the Central African Republic, the DRC, Gabon, Ghana (identified in animals only), Ivory Coast, Liberia, Nigeria, the Republic of the Congo, Sierra Leone, and South Sudan.1 Two clades of monkeypox virus have been identified: the West African clade and the Congo Basin (Central African) clade.1 · Human monkeypox cases are increasingly reported in West and Central Africa, likely due to increased exposure to infected animals as a result of deforestation, conflict and displacement; waning immunity of smallpox vaccine, a growing population unimmuned against smallpox, as well as improved surveillance and laboratory capacity in the African region.4,5 · The first occurrence of monkeypox outside the endemic area in Africa was in 2003,6 with 47 confirmed and probable human cases in the United States (US) infected via close contact with pet mammals (mainly rodents) carrying the virus. The probable source of the outbreak was attributed to the importation of small mammals from Ghana to Texas, with further spread to other states via pet prairie dogs housed with the infected rodents. No further human-to-human transmission was identified in this 2003 outbreak.7,8 Multi-Jurisdictional Monkeypox Outbreak 2022 – What We Know So Far 3 · In May 2022 up to May 27, over 400 confirmed and 97 suspect (including possible, probable, suspect) monkeypox cases have been reported from 28 countries.9 This unexpected large number of confirmed and suspect cases of monkeypox in a short duration of time with no direct travel links to the monkeypox endemic area is unusual, and suggests that community transmission has been going on for some time undetected. This has given rise to an urgent