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Irish and UK based scientists comment on the first case of Clade 1 Mpox detected in Ireland.
Prof Eoin Feeney, Consultant in Infectious Diseases, St. Vincent’s University Hospital and Clinical Professor, University College Dublin, said:
How significant is this?
“Mpox is a viral infection typically spread by close personal contact. Symptoms can include a rash, blisters, fever, muscles aches and swollen lymph glands. There was a global outbreak of clade II mpox infection in 2022 (clade is a subgroup or subtype of virus), which predominantly affected gay and bisexual men who have sex with men (gbMSM). This outbreak was controlled although occasional cases continue to be reported in Ireland and elsewhere (https://www.hpsc.ie/az/sexuallytransmittedinfections/publications/stireports/HIV,_mpox_&_STI_trends_in_Ireland_Report_Website_Week1-52%202024.pdf).
“There has also been a large, ongoing clade I mpox infection in central Africa since 2022, mostly in the Democratic Republic of the Congo (DRC). This outbreak has affected men, women and children. Imported clade I infections have been detected in the US, Sweden, the UK and Germany among other countries. There is no evidence of ongoing clade I transmission outside central Africa.
“A case has now been reported in Ireland in an individual who has returned from the DRC. This is the first clade I infection identified in Ireland. Clade I infections are usually more severe than clade II infections, although the risk remains low.”
What level of risk is there?
“This case shows that the patient has been correctly tested and identified and is being treated in a local hospital. Close contacts of the patient are being assessed. The risk to the general public is very low.”
What should people be aware of?
“People should be aware that the HSE offers mpox vaccination for those at risk of mpox, such as gbMSM and laboratory and healthcare workers who may come in contact with mpox. Vaccinations are happening at sites including at St. Vincent’s University Hospital, Mater Misericordiae University Hospital, St. James’ Hospital and Galway University Hospital (https://www2.hse.ie/conditions/mpox/).
“Anyone returning from an area where there is ongoing mpox transmission should be vigilant for symptoms for 3 weeks and seek medical attention if concerned.”
Prof Michael Marks, Professor of Medicine at the London School of Hygiene & Tropical Medicine (LSHTM); and Honorary Consultant in Infectious Diseases at the Hospital for Tropical Diseases, University College London Hospital, said:
“Given the ongoing large outbreak in DRC and neighbouring countries we will continue to see occasional ongoing importations to other regions of the world as we have in UK, Europe and elsewhere. For most people, the risk of severe illness from Clade 1 mpox remains very low and the risk of onward transmission to the general public is also low. I anticipate we will continue to see such cases and public health authorities in UK, Ireland and elsewhere have activated relevant surveillance and testing systems to enable timely detection of these. Overall, the critical issue remains the ongoing huge burden of mpox in Africa which is where the morbidity and mortality associated with this infection is occurring.”
Prof Paul Hunter, Professor in Medicine, UEA, said:
“Not that surprising. There have been several cases in Europe and North America: 7 Germany, 6 UK, 2 Belgium and the US, and 1 in Sweden, Canada and France. So 20 cases in total but no deaths. Of these 20 cases, 13 had a history of travel to Africa and the remaining 7 were close/household contacts of one of these cases (see below). The UKHSA give different counts for England 9 cases all of which were associated with travel to Africa https://www.gov.uk/government/publications/monkeypox-outbreak-epidemiological-overview/mpox-outbreak-epidemiological-overview-6-february-2025. Explained by 4 new cases in January three of which will be included in upcoming WHO reports.
“So, any country that has its citizens travelling to Africa is likely to see someone arriving back with the infection at some point.
“The big issue is whether this poses a risk of wider spread within the population. We had an pandemic with clade 2b back in 2022 and that clade is still spreading globally (there were over 200 reports in 2024). But that infection is primarily spreading in sexual networks were people have multiple partners. Since then, many people on that risk group have already had mpox or been vaccinated. Immunity to clade 2b, whether from infection or vaccine also gives immunity to clade 1b. So although spread with 1b may occur in that group we are unlikely to see the numbers we saw in 2022.”
Prof Trudie Lang, Professor of Global Health Research and Director of The Global Health Network, University of Oxford, said:
“This case in Ireland is unfortunate and worrying news, however the systems should be in place to prevent further transmission, follow up all contact and provide this participant with optimum care and support and so the wider risks are low. But this should remind the world that the crisis is not over with this new variant of mpox, and it is still a very real burden in Africa and is causing dreadful impact in communities where transmission is still occurring. One worrying change observed in South Kivu in DRC is that there are more cases in children than adults and the causes of this shift need to be explored and understood.”
Dr Jake Dunning, Senior Research Fellow and Consultant in Infectious Diseases, Pandemic Sciences Institute, University of Oxford, said:
“It’s not surprising that Ireland has identified a clade I mpox case. It’s expected that European countries will see occasional cases that are associated – directly or indirectly – with the ongoing clade I outbreaks in Africa, and particularly with recent travel to affected countries in Africa. This is evidence that Ireland’s public health and healthcare systems are doing what they are designed to do when it comes to emerging infections. There is no evidence of a wider outbreak in Ireland, so there is no cause for alarm and authorities have assessed the risk to the population in Ireland as being low. Mpox is spread by close contact, so I expect the Irish authorities will be trying to identify, risk-assess, and provide support and advice to anyone who had close physical contact with the affected individual while they have been infectious. The UK has detected nine cases of clade Ib mpox to date. Onward transmission of clade Ib mpox has occurred in the UK, but, to date, only within a household (a setting where sustained close physical contact often occurs).”
Prof Thomas House, Professor of Mathematical Statistics, University of Manchester, said:
“It is not surprising to see a case of clade 1 Mpox in Ireland; since the increased global spread of this virus in 2022, there has been no reason to think that any country will see no domestic infections. The four different clades of Mpox, 1a, 1b, 2a, and 2b, are associated with different disease severities and seen in different contexts, but from the point of view of most people they are not so different as to require different responses. We know that the primary route of transmission is close skin-to-skin contact, although other routes are possible, and so people who have a lot of sexual contacts are at increased risk of infection. A vaccination is available that is safe and effective at reducing infection risk and severity; it seems that neither infection nor vaccination confers lifetime immunity but both do reduce likelihood and severity of later infection. Prevalence of Mpox is higher in DRC primarily due to higher levels of infection in non-human hosts. The previous name “Monkeypox” was misleading because rodents are much more important hosts than primates, and a person can become infected after handling an infected rodent they have trapped, for example. At present, the risk to the general population is low, but we cannot rule out something changing in the future to enable wider spread. This is always a small but present risk for all viruses that humans catch from other animals. If we want to reduce this risk as well as the known harms of Mpox in humans, we can distribute vaccines more widely, both in the African areas where risks are greatest, and to at-risk populations elsewhere, as well as encouraging evidence-based measures to reduce infection risks.”
Dr Jonas Albarnaz, Institute Fellow, Capripoxvirus Biology, The Pirbright Institute, said:
Media reports are reporting the HSE in Ireland has said the individual had recently returned to Ireland from the DRC – does this mirror what has happened in other countries recently?
“Sporadic cases outside Africa are expected to happen whilst the outbreak is not brought under control in Africa. Other than the Democratic Republic of Congo (DRC), clade 1b mpox has also been transmitted locally in other African countries like Burundi and Uganda. Therefore, this new case in Ireland imported from DRC indicates the ongoing outbreak of clade 1b in this African country.
“Since the emergence of clade 1b mpox in East DRC, countries implemented surveillance and contact-tracing strategies to detect possible importations early on, following WHO recommendations. These measures enabled the detection of imported clade 1b cases in Sweden, Thailand, India, Germany, US, UK, Canada, France, China, and now Ireland in individuals with recent travel history. However, only limited secondary transmission to close contacts has been reported in countries outside Africa.
How worrying is this?
“Strains of monkeypox virus, the pathogen causing mpox, are classified in 2 major clades defined by genetic differences between them. Clade 1 virus is associated with a more severe disease and higher mortality rates than the clade 2 virus responsible for the international mpox outbreak in 2022. An outbreak of clade 1 virus is ongoing in DRC since 2023, with thousands of cases suggesting that there’s sustained human-to-human transmission there. A significant number of cases among children has been reported in this outbreak in the DRC as well. The emergence of the new clade 1b variant in East DRC in 2024 changed this picture as cases have been reported outside DRC (Burundi, Kenya, Rwanda). Most of the clade 1b has been in young adults, and sexual networks seem to be driving its spread. However, there is no evidence that this variant transmits more readily or causes a more severe disease than clade 1a.”
Declared interests
Prof Eoin Feeney: “Receipt of HRB funding for MpoxVax, a study looking at immune response to vaccination to prevent mpox.”
Prof Michael Marks: “I don’t believe I have any relevant COIs although I am the lead investigator on an EU funded study about the mpox outbreak in DRC”
Prof Paul Hunter: “No COIs”
Prof Trudie Lang: “No conflict of interest”
Dr Jake Dunning: “None.”
Prof Thomas House: “None.”
Dr Jonas Albarnaz: “No conflict of interests to declare.”