Health authorities across the UK are issuing a stern warning about a troubling rise in mpox cases, specifically involving the clade 1b mutation, which has been observed spreading throughout Europe and the United States. This particular strain is significantly more severe, carrying a fatality rate of up to one in 100 infected individuals, and is tragically linked to a wave of miscarriages reported in Africa, where it first emerged.

The UK Health Security Agency (UKHSA) has confirmed the presence of small numbers of clade 1b cases in Spain, Italy, the Netherlands, Portugal, and the US. A significant concern for health officials is the lack of a clear epidemiological link between these detected cases and countries known for clade 1b transmission, strongly suggesting that the rash-causing virus may be spreading silently and undetected across the globe. Adding to this concern, a new pattern of transmission has been observed, with most identified cases occurring among gay and bisexual men, a demographic where this specific strain hadn't previously been noted.

In response to this emerging threat, UKHSA officials are urgently advocating for all eligible individuals in the UK to receive the mpox vaccine to prevent a potential widespread outbreak within the country. This call echoes the lessons learned from the 2022 global mpox outbreak, which involved a different, less severe strain known as clade II. That outbreak, primarily transmitted through sexual contact among gay and bisexual men, prompted a global health alert but eventually subsided thanks to increased public awareness and rapid vaccination efforts. During the 2022 event, the UK recorded nearly 4,000 cases, with NHS England vaccinating over 68,000 people using the smallpox vaccine, which is effective against mpox due to the close genetic relationship between the viruses.

Dr. Katy Sinka, Head of Sexually Transmitted Infections at UKHSA, underscored the importance of vaccination, 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.' She emphasized that while mpox can be mild for some, it can also be severe, making vaccination a 'proven effective way to protect yourself against severe disease.' Similarly, Richard Angell, Chief Executive of the Terrence Higgins Trust, highlighted the painful and unpleasant nature of the mpox rash, particularly in intimate areas, and praised the current government-funded vaccine program, especially for gay and bisexual men with multiple partners or those who frequent sex-on-premises venues.

Clade 1b first appeared last year and has since devastated central African nations, infecting tens of thousands, with the Democratic Republic of Congo, Burundi, Rwanda, Uganda, and Kenya being particularly hard hit. The World Health Organization (WHO) declared this ongoing outbreak in central Africa a 'public health emergency of international concern,' a designation previously given to Covid-19. However, experts anticipate that the high fatality rates observed in central Africa are unlikely to be replicated in developed nations like the UK due to superior healthcare access and systems.

Since October 2024, the UK has reported 16 cases of clade 1b, all within England, and all with direct or indirect travel links to countries where the strain is circulating. More recently, Spain reported its first locally-acquired cases, and an additional four cases were reported to the European Centre for Disease Prevention and Control (ECDC) among men in Italy, Portugal, and the Netherlands. Significantly, these five individuals had no travel history, leading the ECDC to suggest a 'different pattern of transmission' possibly within sexual networks among men who have sex with men across several EU/EEA countries.

Mpox infection typically manifests with characteristic lumpy lesions, fever, aches, pains, and fatigue. In a smaller number of cases, the virus can invade the blood and lungs, as well as other organs, leading to life-threatening complications. While current mpox vaccines (derived from smallpox vaccines) were successfully used against the milder clade II strain during the 2022 outbreak, their effectiveness against the more potent clade 1b strain has yet to be widely studied. Nevertheless, UKHSA expects vaccine protection against clade 1b. The WHO and NHS recommend vaccination within four days of exposure or up to 14 days if asymptomatic. Healthcare workers and men who have sex with men are advised to get vaccinated even without known exposure. Currently, there are no direct treatments for mpox, with medical interventions focused on supportive care to help patients fight the virus.