Manitoba detects 1st confirmed case of recently identified mpox strain in Canada

Manitoba has detected what is believed to be the first confirmed case of a recently identified lineage of mpox in Canada. 

The province said Friday it has identified the first confirmed case of clade Ib mpox, formerly known as monkeypox, in the province.

There are two main forms of mpox virus: clade I and clade II. 

“Clade” is a virology term, similar to the variants used to describe offshoots of SARS-CoV-2, the virus behind COVID-19, which gives scientists a way to track each virus’s evolutionary family tree.

The global mpox outbreak in 2022 was dominated by clade II, which typically leads to milder illness and spread around the world through sexual contact. 

A Health Canada page, last updated on Oct. 31, said to that point, there had been no confirmed cases in Canada of clade I, which is divided into two subclades: clades Ia and Ib.

The news release from the province said the clade Ib case discovered in Manitoba is the first case of clade I mpox in Canada.

The Manitoba case is travel-related and associated with an outgoing outbreak of clade I mpox in central and eastern Africa.

Clade I mpox has long circulated within Congo. It’s been linked to more serious disease and higher death rates, but historically spread mainly from infected animals to people in the country’s rural regions, often striking vulnerable children. 

By April this year, a Canadian-Congolese research team had identified a new lineage — known as clade Ib — which showed signs of efficient human-to-human transmission and was striking high numbers of sex workers. At the time, the team warned it could soon spread beyond Congo.

Several cases of the travel-associated mpox clade I subclass Ib have been reported in other countries, including recently in the United States, the province of Manitoba said in its news release.

The person infected was assessed and diagnosed shortly after returning to Manitoba and is currently isolating, according to the province.

It said due to the risk of identifying the individual, it will not release any further identifying information, but said a public health investigation, including contact tracing, is ongoing.

The overall risk to the general public is low, according to the province.

Mpox often causes mild disease, and is known for its namesake pox lesions.

It can cause a painful rash, enlarged lymph nodes, fever and other symptoms, the province said in its news release.

While most people fully recover, some get very sick.

Mpox does not spread easily between people unless there is close contact with someone who has symptoms, Friday’s news release said.

Both clades of mpox spread from person to person through close contact, including sexual contact, with an infected person, or through contact with contaminated materials, such as bed sheets or towels, and contact with infected animals, the province said.