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While it gets less attention than H5N1, the WHO declaration of a PHEIC (Public Health Emergency of International Concern) remains in place for the Mpox Clade Ib virus, and the number of countries outside of Central Africa seeing imported cases continues to rise.
Yesterday Switzerland became the latest European country to report an imported case (see announcement from their Federal Office of Public Health FOPH below).
This Ib clade is reportedly more virulent, and potentially more transmissible, than the clade II mpox virus which began its world tour in the spring of 2022. Last February, the WHO published an updated risk assessment which put the overall Global Health Risk from clade Ib as High.
On Monday the UK announced their first Mpox Clade Ib case Without Recent Travel or Known Exposure, which - while still only one case - raises concerns over the potential community transmission of this emerging clade of the virus.
Expert reaction posted on the Science Media Centre from Dr. Jonas Albarnaz, Institute Fellow, Capripoxvirus Biology, The Pirbright Institute, included the following quote:
So far, the clade 1b cases in the UK have been in individuals with recent travel history to Africa and their household contacts. The detection of a clade 1b case in a person without travel history or contact with the other clade 1b cases is surprising. Public health authorities should investigate how this recent case was acquired, but it’s likely that it was acquired from another infected person, via direct contact either with skin lesions or with contaminated surfaces or objects.
Yesterday Hong Kong's CHP issued a lengthy statement in response to this latest development (excerpts below).
In response to the detection of a confirmed case of new Mpox (also known as Monkeypox) strain (Clade Ib) who was suspected locally infected in the United Kingdom (UK), the Centre for Health Protection (CHP) of the Department of Health (DH) today (April 8) reminded members of the public to heighten vigilance, avoid close physical contact with persons suspected of contracting Mpox and seek medical advice as soon as possible if symptoms appear. High-risk target groups are advised to receive Mpox vaccinations.
According to the UK Health Security Agency, a patient residing in the North East of the UK was confirmed positive for new Mpox strain (Clade Ib) last month (March). The patient had no travel history prior to the onset of symptoms and no reported link with previously confirmed cases. The UK health authority has followed up contacts of the patient and no further cases identified. This is the first case in which a new Mpox strain has been detected outside Africa but without links with case in Africa.
Following the discovery of the new Mpox strain (Clade Ib) with sustained transmission in Africa at the end of 2023, it has exported to countries outside Africa. At present, there are imported and import-related cases identified in 15 countries in Asia, Europe and North America, with the vast majority of cases having travel history to Africa. There is no evidence of large-scale outbreaks of new Mpox strain (Clade Ib) outside Africa at the moment.
Hong Kong has not yet detected any new Mpox strain (Clade Ib) cases. Since 2022, a total of 72 Mpox cases (58 local and 14 imported) have been recorded in Hong Kong, of which four cases were recorded this year. All cases were male. Epidemiological investigation showed that most cases involved men who have sex with men (MSM) or bisexual with history of high-risk sexual behaviours, including having sex with strangers or unsafe sex.
Hong Kong has put in place the Preparedness and Response Plan for Mpox (the Plan) since June 2022. Subsequent to the confirmation of the first Mpox case in September 2022, the Government activated the alert response level under the Plan and implemented preventive measures accordingly, including enhanced surveillance, strengthening port health measures, quarantine preparedness and hospital preparedness. Mechanisms are in place in Hong Kong to ensure swift and interdepartmental responses to public health threats from Mpox when necessary.
Although the first PHEIC issued in the summer of 2022 over the international spread of the Clade IIb, Mpox virus was rescinded in 2023 following steep declines in cases (due largely to uptake of the Mpox Vaccine and behavior changes), we continue to see signs of its resurgence.
Yesterday Vancouver's Coastal Health issued a bulletin warning of increasing numbers of cases in recent months.
Mpox continues to circulate in the VCH region, especially among people not vaccinated or under-vaccinated
April 8 2025
Vancouver, B.C. — Mpox remains a public health concern in the Vancouver Coastal Health region, with a recent increase in cases, predominantly among gay, bisexual and other men who have sex with men (gbMSM) who have not received two doses of ImvamuneTM, the vaccine used for the prevention of mpox.
Caused by the mpox virus, the disease is endemic in parts of west and central Africa, where transmission historically has primarily been from infected animals to humans. Since May 2022, one of the African strains (Clade 2) has spread to more than 70 countries where it is exclusively spread from person-to-person.
According to data from the BC Centre for Disease Control, in 2024, 96 cases of mpox were reported across B.C. (compared to 190 in 2022) with an additional 19 cases reported in 2025 to date. Most cases in the province (77% in 2024 and 68% in 2025) have been among VCH residents.
More than half have occurred among those who are not immunized or who had received only one dose of the recommended vaccine (62% in 2024 and 52% in 2025). While cases can occur among those who have received two doses of vaccine, these individuals tend to have milder symptoms than those who are unvaccinated. However, they can still transmit the infection to others. There have been no hospitalizations from mpox in 2024 or 2025, and no deaths reported in B.C. to date.
With the recent rise in cases, the spread of infection continues to be through person-to-person transmission, primarily affecting gay, bisexual and other men who have sex with men (gbMSM). Symptoms usually appear one to two weeks after exposure but can take anywhere from five to 21 days to appear and can last up to two to four weeks. The infection may start with flu-like symptoms, then one to five days later, a skin rash appears, with lesions that can appear on genitals, hands, feet and/or mouth. The rash may start in one place and spread to other parts of the body.
The Mpox virus continues to evolve, and we now have at least 4 clades of Mpox in circulation (I, Ib, II, IIb), with Clade Ia and Ib considered the most severe.
While the threat remains limited, as our collective immunity from the smallpox vaccine - which was discontinued in the late 1970s - wanes, there may be increased opportunities for poxviruses to make a comeback.
One of the realities of life in this third decade of the 21st century is that the world is a lot smaller than used to be. Vast oceans and extended travel times no longer offer the protection they once did, and there is no technological shield that we can erect that would keep an emerging virus out.
Today you can literally hop on a plane and be in any corner of the world within 24 hours. Millions of airline passengers make international flights each day, and along with their luggage and cell phones, a small percentage will be carrying infectious diseases.
Most viral infections have a 2 to 14 day incubation period, giving an infected traveler a fairly long asymptomatic `window' for travel.
As we've seen with MERS-CoV, Mpox, H5N1, and Ebola - most of these viral introductions have failed to take root - but the rapid global spread of the SARS-CoV-2 virus in early 2020 illustrates how quickly the status quo can change.
