Monkeypox: What is it and how does it spread?

A growing number of countries, including Canada, the U.S., Spain, Portugal, and the U.K, are reporting an unusual outbreak of monkeypox. What makes these cases notable is the disease is relatively rare and there are no clear links between some of the infections, raising concerns about community spread and undetected cases.

Due to the unexpected nature of the current outbreak, health officials may be looking at whether there are any changes from what was previously known about the illness, including incubation period and method of transmission.

Assuming the virus is behaving similarly to previous outbreaks, this is what we know about monkeypox, based on information from Health Canada, the U.S. Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and an interview with Dr. Lisa Barrett, an infectious diseases specialist and assistant professor at Dalhousie University’s Medicine School.


First discovered in 1958, monkeypox is a rare disease caused by a virus that belongs to the same family as the one that causes smallpox. The disease was first found in colonies of monkeys used for research. The first human case was not recorded until 1970, when it was identified in the Democratic Republic of the Congo in a young child, two years after smallpox had been eradicated in the region.

The disease has primarily been reported in central and western African countries, with the first case outside the continent reported in 2003 in the United States. That outbreak was traced to contact with pet prairie dogs that had been infected after coming in close contact with animals imported from Ghana. Cases outside Africa remain extremely rare, and are typically linked to international travel or imported mammals.

The natural reservoir, or main carrier of the virus is not known, since the virus has only been isolated twice from a wild animal, once in 1985 in an African rodent and another time in 2012 in a non-human primate, but it is believed to occur naturally in tropical jungles around Western and Central Africa.


Monkeypox has historically been transmitted from animals to humans, with a small circle of close contacts around the individual also becoming infected, keeping the outbreak and number of cases fairly contained, said Barrett, but the current situation is unusual.

“This is different … multiple places, multiple parts of the globe, more cases and the type of contact in certain parts of this particular outbreak seem to be different,” she told

“It’s very uncommon to see that much spread outside of a geographic area at the same time, and these are pretty closely linked in time.”

The WHO says that no source of infection have been confirmed and that based on currently available information, infectious appears to have been locally acquired in for the U.K. cases.


The virus is transmitted through contact with an infected animal, human or contaminated material. Transmission between people are thought to primarily occur through large respiratory droplets, which generally do not travel far and would require extended close contact. Transmission from an animal can happen through bites or scratches, contact with an animal’s blood or body fluids.

In both scenarios, infection is also possible through direct contact with body fluids or material like clothing or bedding. Broken skin – even microscopic abrasions, and mucous membranes like the eyes can all be entry points for the virus. Like COVID-19, it can enter through the respiratory tract.

Anyone can catch it, but historically, children under the age of 16 have made up the largest proportion of cases.

Previously, the longest documented chain of infection was four generations of person-to-person transmission, Health Canada notes, suggesting that it has “limited potential for epidemic spread.”

It is too soon to know if the known modes of transmission have evolve with the current situation, according to Barrett. She notes that the virus was slightly different in each of the previous outbreaks.

“So could it well be that this is a slightly different version 20 years later? Sure, of course it could be,” she said.

“How important that is, versus that this is a social change or difference in how the transmission is occurring, is not clear yet. So there’s a combination of virus factors and people factors that may be different here.”

A number of the current cases have been detected in men within the LGBTQ2S+ community, according to health officials, but health experts have been cautious about drawing conclusions. Clusters in the current outbreak have been associated with close contacts and not all of the cases have been sexually linked.

“It’s really important for people to know it’s contact with body fluids, whether that’s a respiratory droplet, or saliva, or some of the fluid that comes from the blisters when they break. That’s the way this spreads,” Barrett said.

“You can have absolutely no sex and very possibly get the monkeypox virus … but close contact can include sex.”

Dr. Michael Skinner, a virologist with Imperial College London’s Department of Infectious Diseases, said in an article on the university’s website that it was too early to make conclusions and assumptions about sexual activity being the mode of transmission.

“Typically, we would exclude other causes before jumping to the conclusion that sexual transmission of an infection has occurred,” he said, noting that this is the first time monkeypox has been seen in this group.

“By nature, sexual activity involves intimate contact, which increases the likelihood of transmission, whatever a person’s sexual orientation and irrespective of the mode of transmission.”


It usually takes about seven to 17 days from the time a person is infected to when they begin showing symptoms, though it can be as short as five days and as long as 21 days.

The infection usually lasts between two to four weeks.

Like other respiratory viruses, a person can transmit the virus when they have a fever. There is also a lot of virus in the fluids in the blisters as well.

“When that little blister is weeping, it is very infectious, so until the final crusts are gone … and all of it is healed, there is some potential for infectiousness and we say to keep it covered,” Barrett said. 


Monkeypox symptoms are similar to those for the smallpox, but generally milder. The first signs are fever, headache, muscle aches, backaches, chills, and exhaustion. One distinguishing feature specific to monkeypox is that an infection also causes lymphadenopathy – the swelling of the lymph nodes.

The “pox” develops after the onset of a fever and usually occurs between one to three days later, sometimes longer. A rash usually begins on the face and spreads to other parts of the body. It starts off as flat patches of skin where the colour has changed (macules) before developing into distinct, raised bumps up to about one centimetre in size (papules). They then become filled with fluid (vesicles) that eventually becomes what is commonly known as “pus” (pustules) before eventually turning into scabs and falling off.

While most of the lesions are usually around the trunk of the body, it can spread to the palms and soles of the feet, and can also develop in the mouth, tongue and genitalia.

Milder cases may even go undetected.

If it is behaving similarly to previous monkeypox outbreaks, the lesions are generally not painful nor super itchy, though the WHO notes that they can be quite itchy or painful in severe cases.


Transmission can usually be avoided if you do not come in contact with materials or animals that could carry the virus, or animals that are sick and found in areas known to have monkeypox. Be mindful if you are traveling to areas that have had known cases, Barrett said.

“At this point, it is not thought that there are enough cases around for us to be changing anything about our general population movements.”

Good hand hygiene, like handwashing with soap and using hand sanitizer, also helps, along with wearing protective equipment when caring for someone who is infected.

Patients infected with the virus should be isolated as they will be infectious during various stages of the illness.

Barrett also recommends reporting it if you have a case, not only so you can get help and support, but also to prevent spread. 


There is no proven treatment for the virus infection, according to the CDC, but the smallpox vaccine is known to also protect against monkeypox, with a greater than 85 per cent efficacy. Because the smallpox vaccine eradicated the disease, however, routine smallpox immunization for the general population ended in Canada and the United States in 1972.

Vaccinating with the smallpox vaccine within four days and up to 14 days after initial contact with a confirmed case may help prevent disease. There is also a newer vaccine that was approved for the monkeypox in 2019, but the availability is limited. The WHO also notes that an antiviral agent known as tecovirimat developed for smallpox was licensed for monkeypox in 2022 by the European Medical Association, but is not yet widely available.

In Africa, one to 10 per cent of those infected with monkeypox die. Death rates are higher among children. A West African version and Congo Basin version have been identified, with the Congo Basin one considered much deadlier, accounting for the higher fatality rate. The WHO says that the case fatality ratio in recent times has been around three-to-six per cent. The suspected cases in Montreal and other overseas cases appear to involve the milder one.

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