Monkeypox outbreak in Europe, <scp>UK</scp>, North America, and Australia: A changing trend of a zoonotic disease

Abstract

While the COVID pandemic is still raging in some parts of the world, a global outbreak of monkeypox appeared as an additional public health threat. Monkeypox is a zoonosis caused by monkeypox virus, a double-stranded DNA virus that belongs to the Orthopoxvirus genus same as other viruses such as variola virus (the causative agent of smallpox) or vaccinia virus. In May 2022, an outbreak of monkeypox was reported in more than 20 countries of the European Union, in the UK, North America, and Australia with more than 340 suspected or confirmed cases. The peculiarity of this outbreak, which is the largest and most widespread that has been reported outside Africa so far, is that the transmission in the majority of the cases occurs through human-to-human contact with no connection with travels to African countries where the disease is endemic.1 Monkeypox virus was identified for the first time in 1958 in monkeys; however, rodents have been identified as the main viral reservoir. The disease induced by monkeypox virus was diagnosed for the first time in humans in 1970 in the Democratic Republic of the Congo where monkeypox is considered an endemic disease. Other areas such as Central and West Africa are also commonly affected by the disease. The most frequent mode of transmission of monkeypox virus involved contact with infected animals. However, human-to-human infection, although less recognized, is also possible. The mortality rate due to monkeypox has been reported as 1%–10% in Africa.2 A recent systemic review found that monkeypox cases have increased 10-fold since 1970 in Africa and sporadic outbreaks outside Africa have been reported from 2003 to 2021. The cases outside Africa were reported in the United States (49 cases: 47 in the initial outbreak in 2003 and 2 cases in 2021), the UK (7 cases), Israel (1 case), and Singapore (1 case),3, 4 which represent a total of 58 cases in 18 years (Figure 1). Many of these cases were described in individuals who traveled from African countries affected by monkeypox, but cases of human infection due to contact with pets infected by rodents imported from Africa were also described.5, 6 After these sporadic cases, the largest international outbreak of monkeypox occurred in 2022. As of 21 May 2022, World Health Organization has reported 92 laboratory-confirmed monkeypox cases in non-endemic countries . Countries reporting the majority of the cases are the UK (21–30), Spain (21–30), Portugal (21–30), followed by Australia, Belgium, the USA, Canada, France, Germany, Italy, Netherlands, and Sweden with 1–5 cases each.1 The current data of 92 confirmed cases in 18 days (from 3 May to 21 May 2022) in 12 countries outside Africa contrast sharply with the 58 cases described during the previous 18 years in 4 countries outside Africa (Figure 1). The transmission of monkeypox virus can occur via respiratory secretions, such as respiratory droplets in close human-to-human interactions or through direct contact with mucocutaneous lesions. The virus can also be transmitted through direct contact with body fluids during sexual relations, which has been proposed to be the most likely mode of person-to-person transmission in the initial cases of the international outbreak in May 2022, mainly men who have sex with men.1 The incubation period has been estimated to range between 5 and 21 days. Symptoms can include fever, malaise, headache, chills, and lymphadenopathy. A rash similar to that of smallpox appears lasting from appearance to desquamation between 14–28 days. Monkeypox rashes can range from 0.2 to 1 cm diameter, they often appear first on the face, but they can then spread through the entire body following a centrifugal distribution. Like smallpox, monkeypox rashes on palms and feet soles are very common.7 Although monkeypox is self-limiting and it has a low transmission rate since it requires close contact between individuals, the current international outbreak with an infrequently high number of cases have raised the alarms of international health authorities. It is known that smallpox vaccine is protective against monkeypox virus with an efficacy rate of 85%.7 In that sense, the cessation of smallpox vaccination due to the eradication of smallpox in 1980 has been proposed as one of the possible causes of the increase of cases in Africa and the outbreaks outside this continent, such as the current one.7 Other factors such as deforestation, climate, or demographic change can potentially promote greater contact between humans and animals that act as a reservoir for monkeypox virus.8 Genetic evolution of monkeypox may also be a causative mechanism.9 With more than 200,000 bases, the genome of the monkeypox virus is 7 times bigger than SARS-CoV-2. It has been a question in our minds, if there is a mutation in the virus to cause the May 2022 outbreak. The virus is being sequenced worldwide, as much as possible and wherever it is isolated, but there is no evidence so far for a major mutation suggesting a reason for the recent spread. In summary, we are facing the largest outbreak of monkeypox outside Africa, having a world population partially protected due to the smallpox vaccine cessation in 1980. Although monkeypox is self-limiting and does not cause a severe disease, the current international outbreak is causing health authorities to consider measures such as quarantine of those infected and the search for ways to produce smallpox vaccine to protect the population without immunity to the virus. PFIS funding (ref: FI21/00037) from Instituto de Salud Carlos III, Spanish Ministry of Science and Innovation (to R.V.). Research grant Talento Investigador of the Community of Madrid, Regional Ministry of Science, Universities, and Innovation, Madrid, Spain (ref: 2019-T1/BIO-12690) (to B.C.) R.V. is supported by a predoctoral contract PFIS (number: FI21/00037) from the funding agency Instituto de Salud Carlos III. Spanish Ministry of Science and Innovation. B.C. is senior researcher in the research program Talento Investigador of the Community of Madrid (number: 2019-T1/BIO-12690). The authors declare no conflict of interest.

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