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Since the first cases of monkeypox in Canada were reported in May, the number of reported cases across the country has increased to 890 as of Wednesday.

The World Health Organization has declared monkeypox a public health emergency of international concern, which means the disease has the potential for further international spread that could require a co-ordinated global response. And the U.S. government declared it a public health emergency on Thursday, signalling it will direct more resources to address the surge in cases.

To make sense of the risks of disease, which causes symptoms including fever, headache, swollen lymph nodes, and a painful rash or skin lesions, The Globe sought the advice of experts on how to navigate this outbreak.

How is monkeypox spread?

In the current global outbreak, nearly all cases of monkeypox have been spread through close, intimate human-to-human contact, and predominately among men who have sex with men.

According to the WHO, this can happen through respiratory droplets, contact with skin lesions from an infected person, or through contact with recently contaminated objects, such as bedding and clothing. The WHO says transmission via respiratory droplets usually requires prolonged face-to-face contact.

Analysis: As monkeypox cases rise globally, experts say it’s unclear whether outbreak can be contained

It is yet unclear whether the virus can be transmitted through sexual fluids. A new study in The Lancet Infectious Diseases suggested it might be, as it found prolonged shedding of monkeypox DNA in semen, suggesting viable virus, though more research is needed.

How long does the virus live outside the human body?

Monkeypox is part of a family of viruses called poxviruses. These can survive in linens, clothing and on surfaces, particularly when in dark, cool, and low humidity environments, according to the U.S. Centres for Disease Control and Prevention. It notes on its website that one study found live virus in a patient’s home 15 days after it was left unoccupied.

But the mere presence of the virus doesn’t mean it will actually infect someone.

Stephen Hoption Cann, a clinical professor at the University of British Columbia’s school of population and public health, advised not to think about monkeypox in the same way as COVID-19.

Unlike COVID-19, people cannot catch the virus at a grocery store, at a restaurant, or through shared transportation. “This is not really how you’re going to contract this disease,” Dr. Hoption Cann added.

How easily does monkeypox spread?

Infectious disease specialist Allison McGeer said people cannot catch monkeypox from casual contact with contaminated items, like trying on clothing in a store, or from inadequately washed bedding at a vacation rental.

Prior to this current outbreak, data from African countries – where monkeypox is endemic – had indicated the virus was not very transmissible, said Dr. McGeer, a member of the Emerging and Pandemic Infections Consortium and a professor at the Temerty Faculty of Medicine at the University of Toronto.

The virus’ spread has almost always occurred among households, and occasionally in hospitals, where there is close contact with patients’ skin and mostly when patients have had severe disease with many skin lesions, she said.

How long does a person remain infectious?

People are believed to be infectious for roughly two to four weeks, from when symptoms first start to until when their skin fully heals and all the scabs from their lesions or rashes fall off, Dr. Hoption Cann said.

It’s difficult to determine whether people without symptoms can transmit the virus because individuals could unwittingly pass it on if they have a lesion in the mouth or genital area, where it may not be obvious, he said.

He added that the cases occurring now may only cause one lesion, whereas patients in photographs may have hundreds.

Ideally, people should be isolating while they’re infectious, but he said if they must go out in public, they should cover up any area that has a rash or lesion.

Who should get tested?

The primary focus for testing and vaccination is on gay, bisexual and other men who have sex with men, since most infections are currently among this demographic, Dr. Hoption Cann said. Individuals who have had multiple sexual partners, who are not using condoms or have a lot of intimate contact with others should get tested or vaccinated, he said.

However, Dr. Hoption Cann also noted the disease’s spread outside this demographic.

Globally, monkeypox has been reported in some women and children in countries where the virus has not been previously seen, though they still make up a small proportion of cases. (In Canada, 99 per cent of cases are among males and the median age is 36 years, Canada’s Chief Public Health Officer Theresa Tam told reporters last week.)

Canadians can get tested for monkeypox based on a number of factors, including having signs and symptoms of the disease or being exposed to a case, according the Public Health Agency of Canada. Since monkeypox can appear similar to chickenpox or sexually transmitted infections, such as herpes and gonorrhea, it advises people to consult a health provider and get tested.

Provinces and territories are maintaining individual webpages with testing and vaccination information.

How long does it take for the monkeypox vaccine to start to work?

This is still unknown. There are many questions about the timing and protection of the vaccines since those now being used for monkeypox were created for smallpox, Dr. McGeer said.

Even though the vaccines have been tested against monkeypox, these tests were conducted at a time when there wasn’t enough of the disease circulating to be able to do vaccine efficacy studies, she said. Research in animals and immunogenicity studies that measure the immune response in humans do indicate the vaccines are effective against monkeypox, she added. And there is some indication people do benefit from a single dose.

“But we really do not know how effective these vaccines are,” she said.

How much protection does someone have against monkeypox if they were vaccinated for smallpox decades ago?

This, too, is unknown. According to New York State’s Department of Health, smallpox vaccination provides full immunity for three to five years, after which immunity declines.

At this stage, it’s hard to say how much immune protection Canadians who were given a smallpox vaccine now have against monkeypox, Dr. Hoption Cann said. Canada stopped routine vaccination against smallpox in 1972.

“If a person was at high risk, I wouldn’t depend on the vaccine received that many decades ago to protect them,” he said.

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