Health officials across Europe and the UK are sounding the alarm over a new pattern in the spread of mpox, as a particular strain known as 'clade Ib' begins to show signs of local transmission in several European countries. While mpox, previously called monkeypox, is generally considered a mild infection, authorities warn that it can become severe in certain cases, and are urging those at higher risk to ensure they are vaccinated.
According to the UK Health Security Agency (UKHSA), small numbers of clade Ib cases have been identified in Portugal, Spain, Italy, and the Netherlands, as well as in the United States. Notably, this marks the first time that transmission of this strain has been observed within sexual networks of gay, bisexual, and other men who have sex with men (GBMSM) in Europe—a shift from previous outbreaks. As reported by Sky News on October 27, 2025, and echoed by the BBC, the UKHSA is closely monitoring the situation and has ramped up its vaccination campaign among those most at risk.
Dr. Katy Sinka, head of sexually transmitted infections at UKHSA, emphasized the urgency of the situation, stating, "The ways in which we are seeing mpox continue to spread globally is a reminder to come forward for the vaccine, if you are eligible." This message is being reinforced by public health campaigns and charities alike, particularly as the autumn and winter Pride event season approaches in Europe. Richard Angell OBE, chief executive of the Terrence Higgins Trust, added, "With Winter Pride season soon upon us across Europe, those travelling to these events would be wise to get vaccinated, at least once, if not twice."
The UK currently has a routine mpox vaccination program in place for specific groups at higher risk of infection. This includes men who have multiple sexual partners, those who participate in group sex, and visitors to sex-on-premises venues. The vaccine is also recommended for workers at such venues and anyone who has had or is likely to have close contact with someone diagnosed with mpox. Most individuals are offered two doses of the vaccine, spaced at least 28 days apart, with vaccination services readily available through sexual health clinics. The NHS advises calling ahead to local clinics before attending for a vaccine.
While there are no direct studies yet on the effectiveness of the vaccine against the clade Ib strain, existing research shows the vaccine is approximately 75 to 80% effective against clade II. Health officials expect a similar level of protection for clade Ib, given the similarities between the strains. The UKHSA's latest technical assessment, dated December 19, 2024, raised the probability of importing clade Ib into the UK from medium to high, largely due to increased international travel and the interconnectedness of social and sexual networks across Europe.
To date, there have been 16 confirmed cases of clade Ib mpox in the UK, all in England. Importantly, none of these cases have been linked to transmission within the domestic GBMSM community; instead, each case has had direct or indirect ties to travel in countries where the strain is circulating. However, the European Centre for Disease Prevention and Control (ECDC) recently reported locally acquired cases in Spain and additional cases in Italy, Portugal, and the Netherlands, all among men who have sex with men and with no recent travel history. This pattern suggests the virus may now be spreading within sexual networks in several EU/EEA countries, rather than being strictly imported from abroad.
The ECDC noted that these recent cases exhibited only mild symptoms and that, up to now, previously reported clade Ib cases in Europe—about 30 in total—were all imported or clearly linked to imported cases. The emergence of locally acquired infections, especially with no travel history, marks a significant shift and has prompted renewed calls for vigilance and vaccination.
Mpox is typically characterized by a skin rash or pus-filled lesions that can last between two and four weeks. Other common symptoms include fever, headaches, muscle aches, back pain, low energy, and swollen lymph nodes. The virus is primarily spread through close physical contact, including sexual contact, as well as through respiratory droplets (from coughs or sneezes) and contact with contaminated clothing, bedding, or towels. In 2022, a global outbreak of clade II mpox affected many countries, with GBMSM communities particularly impacted.
Although clade Ib and Ia strains of mpox are no longer classified as high-consequence infectious diseases by UKHSA, the infection can still be severe in some individuals. The agency stresses that vaccination remains the best line of defense, especially for those at higher risk. According to the BBC, the risk of onward transmission in the UK is considered low to medium and is likely being mitigated by the ongoing GBMSM vaccination program. However, the increased probability of importation and evidence of local spread in Europe mean that continued vigilance is necessary.
Charities and health officials are particularly concerned about the upcoming Pride events, which are expected to draw large crowds and, potentially, facilitate further transmission. They urge anyone planning to travel to these gatherings to get vaccinated beforehand. As Richard Angell OBE put it, "Those travelling to these events would be wise to get vaccinated, at least once, if not twice."
For those seeking vaccination, the NHS and sexual health services offer guidance and appointments. The vaccine is strongly recommended for individuals who have multiple sexual partners, engage in group sex, visit sex-on-premises venues, work at such venues, or have close contact with someone who has mpox. While the vaccine's efficacy against clade Ib is not yet fully established, experts agree that it remains the best available tool for preventing infection and limiting the spread of the virus.
As Europe faces this evolving challenge, health officials continue to monitor the situation closely. The hope is that robust vaccination efforts and clear public health messaging will keep the outbreak contained and prevent a repeat of the widespread transmission seen in 2022. For now, the message is clear: if you're eligible, get vaccinated—and encourage others to do the same.
