Avian Flu Diary: ECDC Statement & Threat Assessment Brief Following Recent Reports of Local Transmission of Mpox Clade Ib in Europe

#18,921

A week ago Los Angeles County Reported 3 (locally acquired) Clade I Mpox Cases, raising concerns of community spread in the United States. Similarly, last Friday the ECDC reported on a single, locally acquired case of Mpox Clade I in Madrid, Spain.

While local transmission outside of Africa has been reported previously, it has been rare, and most have been traced to known contact with a recent traveler from Africa.

Mpox Clade Ib is a different, and potentially more severe, strain of Mpox which emerged in East Central Africa in late 2023 and should not be confused with the milder Mpox Clade II which began to spread internationally in 2022.

Today the ECDC has announced 4 more recent autochthonous cases of Mpox Clade Ib (Italy =2, Portugal =1, and the Netherlands =1), and has published a Threat Assessment for the EU/EEA.

First the news summary, followed by the link and some excerpts from the Threat Assessment:

Local transmission of clade 1b mpox cases detected in EU/EEA, ECDC urges renewed vigilance
News
24 Oct 2025

Following the first detections of locally acquired mpox clade Ib cases within the European Union and European Economic Area (EU/EEA), the European Centre for Disease Prevention and Control (ECDC) is calling for heightened awareness and targeted prevention measures.

Locally acquired mpox cases have now been confirmed in four countries. Spain reported its first such case on 10 October 2025, and the Netherlands on 17 October 2025. These have been followed by additional cases reported in Italy (2) and Portugal (1). This development is distinct from the previously reported travel-associated clade Ib cases between August 2024 and October 2025, mostly among returning travellers from mpox-endemic areas outside of the EU. These new cases have been reported among men, some of whom identify themselves as men who have sex with men, with no recent travel history to mpox-endemic areas. This indicates that transmission may be ongoing in sexual networks among men who have sex with men in European countries.

Transmission among gay, bisexual, and other men who have sex with men and their social networks has also been recently reported in California, USA, after the detection of three unlinked clade Ib cases.

While the immediate risk to the general population of acquiring the disease is low, the overall risk of infection is moderate for men who have sex with men. The risk of severe disease may be higher for those living with untreated HIV. Some uncertainties remain regarding the transmissibility and clinical severity of clade Ib compared to the clade IIb virus that has circulated since 2022. Among 29 clade Ib cases reported to ECDC before the current cases, seven were hospitalised for treatment, although with such a small number of cases, any estimation of severity in comparison to clade IIb is uncertain.

To prevent further spread, there is a need for a multi-pronged public health response. This includes ensuring testing is easily accessible, especially in sexual health clinics, and that mpox vaccination is actively offered to gay, bisexual and other men who have sex with men. Prompt identification and isolation of new cases and contact tracing to identify contacts and offer them vaccination are essential to control transmission. Public health authorities should work closely with civil society and community-based organisations that serve men who have sex with men to promote awareness and vaccination uptake, using respectful, non-stigmatising language and targeted communication channels.

Mpox is usually acquired through direct contact – such as sex or skin-to-skin contact – with people who have the disease. Vaccination offers the best protection, and individuals at higher risk of exposure, such as gay, bisexual, or other men or transgender people who have sex with men, should seek vaccination proactively. They can check with national health authorities or sexual health clinics for information on who is eligible for vaccination and where to access it.

Doctors should consider offering post-exposure vaccination to close contacts of cases, including sexual partners and individuals with other prolonged physical or high-risk contact, because the vaccine has been shown to confer protection even after exposure.

Sexually active individuals should be aware of the symptoms of mpox and how to protect themselves and others. Symptoms include a typical rash (pimples or blisters) on any part of the body, which can be limited to a few lesions or be widespread, sometimes accompanied by fever, cough, sore throat or other flu-like symptoms or swollen lymph nodes. If an unusual rash develops, they should seek medical help by contacting a healthcare professional for testing and advice. It is also important to avoid close physical or sexual contact with others until they are symptom-free.

Threat Assessment Brief: Detection of autochthonous transmission of monkeypox virus clade Ib in the EU/EEA

Assessment
24 Oct 2025

This Threat Assessment Brief aims to assess the risk of autochthonous transmission of monkeypox virus (MPXV) clade Ib in EU/EEA countries in the context of male-to-male sexual transmission. It is intended for public health authorities in EU/EEA countries and is based on currently available evidence. It therefore carries considerable uncertainty. Recommendations how public health authorities can respond at the country level together with an overview of knowledge gaps in the context of MPXV clade Ib are also included.

Epidemiological situation

On 10 October 2025, Spain reported its first locally acquired clade Ib mpox case. On 17 October, four additional clade Ib mpox cases were reported to ECDC among males without travel history by Italy (two), Portugal (one) and the Netherlands (one). All five cases had mild symptoms. Some of the individuals reported having sexual contact with another male.
These recent cases, where there is no travel history, represent a different pattern of transmission and indicate that transmission may be occurring in sexual networks among men who have sex with men in several EU/EEA countries. The 30 clade I mpox cases reported in the EU/EEA previously were all imported or had clear links to imported cases.

Risk assessment

Based on current evidence, the overall risk of MPXV clade Ib infection is assessed as moderate for men who have sex with men and low for the general population.
It is likely that further cases are present among men who have sex with men in the EU/EEA but have not yet been detected. ECDC will continue to closely monitor and review this risk assessment should the situation evolve into a larger outbreak.
Recommendations

EU/EEA countries should ensure laboratory testing is easily accessible, particularly in locations that serve men who have sex with men, and that clinicians and laboratories can report cases to public health authorities rapidly.
Identifying clades should be done where individuals have been diagnosed with mpox, and clade I viruses should be sequenced as soon as possible.
Vaccination should be made available to all individuals at substantially higher risk of exposure to MPXV, in addition to other preventive measures. Public health professionals should advise individuals om groups at higher risk of infection to seek vaccination proactively.
Contact tracing should be carried out after a case is identified, to enable control of onward transmission as well as to contribute data that will allow for an assessment of transmission dynamics.
Public health authorities should continue risk communication activities around mpox and partner with civil society organisations that serve men who have sex with men to build trust in health services, provide advice on seeking medical assistance and improve vaccination coverage.

Download

Detection of autochthonous transmission of monkeypox virus clade Ib in the EU/EEA - EN - [PDF-672.37 KB]

While largely ignored by the Western world, Mpox has been spreading unchecked, and evolving, in West and Central Africa for decades.

A 2016 study (see EID Journal:Extended H-2-H Transmission during a Monkeypox Outbreak) looked at a large 2013 outbreak of Monkeypox in the DRC and suggested that the virus's epidemiological characteristics may be changing (possibly due to the waning smallpox vaccine derived immunity in the community).

The DRC reported a 600% increase in cases over both 2011, and 2012. The authors also cite a higher attack rate, longer chains of infection, and more pronounced community spread than have earlier reports.

While the 2022 world tour by the milder Mpox clade IIb virus was eventually largely suppressed, it continues today, and reining in clade Ib may prove even more challenging.

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.