Northern Ireland Records First Cases of Mpox Clade Ib Strain as Public Health Agency Urges Vigilance
Northern Ireland's Public Health Agency has confirmed that 21 cases of mpox were detected in the region during June 2026, representing the first recorded instances of the more severe clade Ib strain in Northern Ireland. The cases, which were identified across several Health and Social Care Trust areas, have prompted the PHA to issue an urgent public health advisory urging eligible individuals — particularly gay, bisexual, and other men who have sex with men — to contact sexual health clinics for vaccination. The agency has emphasised that the risk to the general population remains low, but that targeted vaccination and awareness are essential to preventing further spread.
Background
Mpox, formerly known as monkeypox, is a viral disease that was first identified in humans in 1970 and has historically been endemic in parts of central and west Africa. The disease gained international attention in 2022 when a significant outbreak occurred across Europe, North America, and other regions, primarily affecting gay, bisexual, and other men who have sex with men. That outbreak was caused by the clade IIb strain of the virus, which, while serious, is generally less severe than the clade I strains that are endemic in central Africa.
The clade Ib strain, which was first identified in the Democratic Republic of Congo in 2023, is of particular concern to public health authorities because it appears to spread more efficiently through close contact and has been associated with higher rates of severe illness. The strain has been spreading internationally since 2024, and its arrival in Northern Ireland — confirmed by the PHA's June 2026 data — represents a significant development in the regional public health picture.
Northern Ireland's sexual health services, which are delivered through the five Health and Social Care Trusts, have been working to expand vaccination capacity in response to the emerging threat. The mpox vaccine — Imvanex — is available through sexual health clinics and is recommended for individuals at higher risk of exposure, including gay, bisexual, and other men who have sex with men with multiple partners.
Key Developments
The 21 cases confirmed in June 2026 represent a significant increase on previous months, and the identification of the clade Ib strain — rather than the clade IIb strain that drove the 2022 outbreak — has elevated the level of concern among public health officials. The PHA has confirmed that contact tracing is under way for all confirmed cases, and that close contacts are being offered vaccination and monitoring.
The agency has issued guidance to sexual health clinics across Northern Ireland on the management of suspected and confirmed mpox cases, including isolation protocols, testing procedures, and treatment options. It has also been working with community organisations that support gay, bisexual, and other men who have sex with men to ensure that accurate information about the disease and the available vaccine reaches those most at risk.
The PHA has emphasised that the risk to the general population remains low, and that the cases identified in June are concentrated in specific networks where transmission is occurring through close physical contact. However, the agency has stressed that early vaccination is the most effective way to prevent further spread, and has urged anyone who believes they may be at risk to contact their nearest sexual health clinic without delay.
Why It Matters
The emergence of the clade Ib strain in Northern Ireland is a significant public health development that requires a coordinated and well-resourced response. The strain's greater severity compared to the clade IIb strain that drove the 2022 outbreak means that the consequences of uncontrolled spread could be more serious, and the public health response needs to be proportionate to that risk.
Northern Ireland's sexual health services have faced significant pressures in recent years, with waiting times for appointments at sexual health clinics among the longest in the UK. The additional demand created by the mpox outbreak — for testing, vaccination, and treatment — will place further strain on services that are already stretched. The PHA has indicated that it is working with the Department of Health and the five trusts to ensure that additional capacity is made available to meet the increased demand.
The situation also highlights the importance of maintaining robust public health surveillance systems that can detect and respond to emerging infectious disease threats quickly. The identification of the clade Ib strain in Northern Ireland within a relatively short timeframe of its international spread reflects the effectiveness of the region's surveillance infrastructure, and the PHA's rapid response is a positive indicator of the system's capacity to manage emerging threats.
Local Impact
The impact of the mpox cases is being felt most directly in the sexual health services of the five Health and Social Care Trusts. The Belfast Trust's sexual health clinic at the Genito-Urinary Medicine (GUM) clinic at the Royal Victoria Hospital has seen an increase in demand for mpox testing and vaccination, as has the Northern Trust's service at Antrim Area Hospital. The Western Trust's sexual health service in Derry/Londonderry and the Southern Trust's service in Newry are also reporting increased demand. The PHA has confirmed that additional vaccination appointments are being made available across all five trust areas, and has urged anyone who believes they may be at risk not to delay in seeking advice and vaccination.
What's Next
The PHA will continue to monitor the mpox situation in Northern Ireland closely, with updated case data expected to be published on a monthly basis. The agency is working with the UK Health Security Agency and public health authorities in the Republic of Ireland to share information and coordinate the response to the outbreak. A review of the vaccination programme's reach and effectiveness is expected to be completed in August, with the findings informing any adjustments to the public health response. Anyone with concerns about mpox or who believes they may have been exposed is advised to contact their nearest sexual health clinic or to call the PHA's public health advice line.
