Mpox: recombinant virus with genomic elements of clades Ib and IIb – Global situation
- 関係する国／地域
- Global situation
- 初回通知
- 2025-12-05
- 最新の通知
- 2026-02-14
- 通知件数
- 2
公式要約（原文）
Recombination of monkeypox virus (MPXV) strains has been documented in recent months, with two cases of a recombinant strain comprising clade Ib and IIb MPXV reported. Recombination is a known natural process that can occur when two related viruses infecting the same individual exchange genetic material, producing a new virus.
The first case was detected in the United Kingdom of Great Britain and Northern Ireland (hereafter “United Kingdom”), with travel history to a country in South-East Asia, and the second in India, with travel history to a country in the Arabian Peninsula. Detailed analysis of the virus genomes shows that the two individuals fell ill several weeks apart with the same recombinant strain, suggesting that there may be further cases than are currently reported.
Both cases had similar clinical presentation to that observed for other clades. Neither patient experienced severe outcomes. Contact tracing for both cases in the reporting countries has been completed; no secondary cases were detected.
Based on available information, the overall WHO public health risk assessment for mpox remains unchanged: the risk is assessed as moderate for men who have sex with men with new and/or multiple partners and for sex workers or others with multiple casual sexual partners, and low for the general population without specific risk factors.
WHO リスク評価（原文）
Mpox outbreaks must be considered in their local context, with meaningful involvement of affected communities, to ensure an in-depth understanding of the epidemiology, modes of transmission, risk factors for severe disease, viral reservoir and evolution, and relevance of strategic approaches and countermeasures for prevention and control.
Multiple strains of MPXV are circulating through interconnected sexual networks across many countries and settings. Co-infection with different strains, that could lead to emergence of recombinant virus strains, while rare, can be expected. The case in India was infected with the same recombinant Ib/IIb MPXV strain detected in the United Kingdom. Symptom onset in the case reported in India occurred more than two months earlier than the case in the United Kingdom, and the great degree of similarity between their sequences suggests a common evolutionary history. This information has two important implications: i) the origin of the recombinant strain remains unknown; and ii) transmission of this recombinant virus already involves at least four countries in three WHO regions, and is therefore likely to be more widespread than currently documented.
For the cases in the United Kingdom and India, the initial clade differentiation PCR results indicated clade Ib and IIb MPXV, respectively. Thus, clade differentiation PCR assays alone may not reliably identify recombinant MPXV strains, and genomic sequencing is likely to be required for their detection.
Due to the small number of cases found to date, conclusions about transmissibility or clinical characterization of mpox due to recombinant strains would be premature, and it remains essential to maintain vigilance regarding this development.
In light of the limited information available on this recombinant MPXV strain, the overall WHO public health risk assessment for mpox remains unchanged: the risk is assessed as moderate for men who have sex with men with new and/or multiple partners and for sex workers or others with multiple casual sexual partners, and low for the general population without specific risk factors.
All countries should remain alert to the possibility of MPXV genetic recombination. The public health risk posed by any newly detected recombinant strain should be assessed on a case-by-case basis, considering available epidemiological, clinical and genomic information.
通知履歴
- · 2026-DON595
Mpox: recombinant virus with genomic elements of clades Ib and IIb – Global situation
公式要約（原文）
Recombination of monkeypox virus (MPXV) strains has been documented in recent months, with two cases of a recombinant strain comprising clade Ib and IIb MPXV reported. Recombination is a known natural process that can occur when two related viruses infecting the same individual exchange genetic material, producing a new virus.
The first case was detected in the United Kingdom of Great Britain and Northern Ireland (hereafter “United Kingdom”), with travel history to a country in South-East Asia, and the second in India, with travel history to a country in the Arabian Peninsula. Detailed analysis of the virus genomes shows that the two individuals fell ill several weeks apart with the same recombinant strain, suggesting that there may be further cases than are currently reported.
Both cases had similar clinical presentation to that observed for other clades. Neither patient experienced severe outcomes. Contact tracing for both cases in the reporting countries has been completed; no secondary cases were detected.
Based on available information, the overall WHO public health risk assessment for mpox remains unchanged: the risk is assessed as moderate for men who have sex with men with new and/or multiple partners and for sex workers or others with multiple casual sexual partners, and low for the general population without specific risk factors.
- · 2025-DON587
Broader transmission of mpox due to clade Ib MPXV – Global situation
公式要約（原文）
The purpose of this report is to raise awareness about the local transmission of clade Ib monkeypox virus (MPXV) among men who have sex with men (MSM) in countries previously unaffected or to date reporting only cases linked to travel. This report summarizes recent epidemiological developments, response activities, and the associated global public health risk.
The second declaration of a public health emergency of international concern (PHEIC) for mpox was lifted on 5 September 2025. As both MPXV clades I and II and their subclades continue to circulate globally, leading to substantial outbreaks in African countries, WHO continues to advise emergency preparedness and response activities. Multiple modes of transmission underlie ongoing virus circulation, with sexual contact remaining the primary amplifier of transmission in most settings.
Since 5 September 2025, several countries across four of six WHO regions have confirmed clade Ib MPXV infection in individuals with no recent travel reported (WHO African Region, Region of the Americas, the European Region and the Western Pacific Region), most of which are being detected among men who have sex with men, suggesting local transmission, particularly given that infections often manifest with few or no symptoms (paucisymptomatic or asymptomatic cases) leading to undetected onward transmission.
Overall, the surveillance data in most countries is sufficient to detect and respond effectively to mpox outbreaks. However, thorough epidemiological investigation, contact tracing and implementation of public health interventions to control spread remain challenging. Mpox is known to resolve on its own over two to four weeks in most cases. However, timely access to quality healthcare is essential to identify, prevent and manage secondary bacterial infections and other complications. Individuals living with immune suppressive conditions remain at high risk of more severe mpox disease and death, most notably people living with undetected and/or untreated, uncontrolled human immunodeficiency virus (HIV) infection. Men who have sex with men with new and/or multiple partners remain at increased risk of clade Ib and also IIb MPXV infection. WHO assesses the public health risk posed by clade Ib MPXV to men who have sex with men as moderate and the risk to the general population as low in most countries.
Mpox（エムポックス）
clade I・II の2つの大きな系統をもつ M 痘ウイルスによって起こるウイルス感染症です。多くの人は自然に回復しますが、免疫機能が低下している人、妊婦、幼児では重症化しやすくなります。
