With cases reported in a number of countries, the human monkeypox infection is sparking global interest and concern as an emerging infectious disease threat, even amid a slowly escalating COVID-19 pandemic.
What is monkeypox virus?
Monkeypox is a member of a closely related group of viruses in the Orthopoxvirus genus that includes smallpox, cowpox, and camelpox. Monkeypox virus was first discovered in the summer of 1958 as a non-fatal, smallpox-like skin disease of monkeys in captivity at a research institute in Denmark.
The name Monkeypox is a misnomer since terrestrial African rodents (rats and squirrels)) serve as the natural reservoir of the virus, while monkeys and other primates are believed to be casual hosts†
When was monkeypox first reported in humans?
The first known case of human monkeypox infection was reported in 1970 from the Democratic Republic of the Congo in a nine-month-old boy with nonfatal smallpox-like disease.
From that moment on, sporadic human cases have occurred in many Central and West African countrieswhere infections are more common in children and young adults. In countries where monkeypox is endemic (where it is most commonly found), recent increases in cases are believed to be related to: climate change, deforestation† warfare, greater population mobility and declining herd immunity to smallpox vaccination†
How is monkeypox transmitted?
Transfer takes place through close physical contact with animals or peopletheir bodily fluids, contaminated droplets from respiratory secretions or infected skin lesions and indirectly through “fomites” (inanimate objects such as bedding, towels and hard surfaces that may be laden with infectious virus particles).
Animal bites and consumption of animal flesh are common modes of transfer in endemic areas. Secondary infections in unvaccinated close contacts appear in about 12.3 percent household contacts and 3.3 percent of others.
When was monkeypox first reported in non-African countries?
The first cluster of human monkeypox infections outside Africa took place in the United States in 2003† A multi-state outbreak involving 87 children and young adults was attributed to close contact with infected prairie dogs obtained as pets from a pet distributor. The ultimate source of infection turned out to be: imported Gambian rats that transmitted the infection to the prairie dogs† There were no human deaths, although three children had serious illness.
Before 2022, several travel related cases reported in UK, Israel, Singapore and US among persons who had visited Nigeria†
What do we know about the global monkeypox outbreak in non-endemic countries?
On 7 May 2022, public health authorities in the UK were informed about: a case of imported human monkeypox infection in a traveler returning from Nigeria. More than 550 confirmed cases of human infection since then have been reported in the UK and 29 other countries† Cases have been extraordinarily higher among men who have sex with menalthough the virus is not known to be sexually transmitted.
What are the symptoms of monkey pox?
The clinical signs from human monkeypox infection mimic that of smallpox, but are usually much milder. Unlike monkeypox, smallpox is an eradicated disease, has no animal reservoir and usually does not affect lymph nodes.
The incubation period of monkeypox in humans ranges from four to 21 days and is followed by a one to five day phase of fever, chills, sweats, fatigue, and enlarged, tender lymph nodes in the neck and groin.
The next phase includes a multi-stage rash which develops from small patches of skin to papules (tiny bumps on the skin), followed by vesicles (tiny bumps filled with clear fluid) and then pustules (tiny bumps filled with pus). These are most prominent on the face, palms and soles. The pustules disappear through scarring or crusting over the following two to four weeks.
Exposed individuals may also develop a sore throat, cough and/or rash on the mucous membranes of the mouth.
How serious is a monkeypox infection?
The illness is usually mild, although severe illness and death can occur. There are two common genetic variants of monkeypox virus: the Central African variant and the West African variant. death rates of 3.6 percent for the West African variant and 10.6 percent for the Central African variant have been reported in endemic regions.
However, no deaths so far in one of the reported cases outside Africa† All confirmed cases of the 2022 outbreak in the 30 non-endemic countries are due to the West African variant†
Are there any other public health recommendations for monkeypox?
People infected with monkey pox should wear surgical masks and skin lesions should be covered until healed. Items for personal use, such as towels and sheets, may not be shared. Frequently touched surfaces should be regularly disinfected, contaminated clothing washed and contact with household and non-household members avoided until the disease has resolved.
Healthcare workers must use gloves, gowns, and respiratory protection with N95 masks and face shields, and maintain excellent hand hygiene while caring for monkey pox patients. Hospitalized patients with confirmed or suspected monkeypox should be isolated with precautions for airborne transmission, droplets and contact until no longer contagious.
Does the smallpox vaccine protect against monkeypox?
Vaccine against smallpox – before or after administered monkey pox exposure — may prevent or reduce the effects of human monkeypox infection. However, rare but serious side effects have been reported from older generation smallpox vaccines. A newer generation, non-replicating, live vaccine is now available and is considered safe for use in all populations, including those with compromised immune systems†
The Advisory Committee on Immunization Practices of the U.S. Centers for Disease Control and Prevention recommends pre-exposure prophylaxis (vaccination prior to exposure to the virus) with the newer-generation vaccine for laboratory workers performing diagnostic tests for monkeypox, as well as health professionals administering the smallpox vaccine or caring for patients with monkeypox. (To be trade name is Jynneos in the US, Imvamune in Canada and Imvanex in Europe.)
In Canada and other developed countries, people born before 1972 were likely: vaccinated against smallpox† Although post-vaccination immunity tends to decline with age, lifelong immunity appears to be the norm following vaccination against smallpox in otherwise healthy individuals, and cross-protective efficacy against monkeypox is believed to be the norm. 85 percent†
Is Monkeypox the Next Viral Pandemic?
The emergence of infectious diseases such as monkey pox in non-endemic areas has raised a lot of fear in light of our experience with COVID-19.
Monkeypox was a neglected tropical disease until the current outbreak in the developed world. But the trajectory of these cases, coupled with the pattern of transmission in Africa, suggests the virus will not become a pandemic†
The baseline reproduction number (R0), a measure of viral infectivity, where R0 is equal to the number of secondary infections transmitted from a single case in a non-immune population, is 0.6 to 1.0 for the Central African variant, and much lower for the West African variant†
In contrast, the R0 for the Omicron variant of SARS-CoV-2 is about 10 and the R0 for measles varies from 11 to 18† The R0 for the West African variant of the monkeypox virus may be too low to maintain human-to-human transmission outside endemic areas.
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