Public health officials in the United States and Europe are closely monitoring a newer variant of mpox (formerly known as monkeypox) as it begins to spread within communities. While the risk to the general public remains low, the presence of this variant signals an increase in the complexity of detecting and containing the virus.
Identifying the New Variant and Its Spread
The new variant, classified as clade Ib, was first detected in mid-2023 in the Democratic Republic of the Congo and is now circulating in several countries. In October, California reported three cases within its communities – two in Los Angeles and one in Long Beach – all of which required hospitalization. Notably, none of the patients had recently traveled internationally or showed connections to each other, suggesting a potential for undetected community transmission. Six cases linked to travelers have also been identified in the US, but these are the first signs of local spread.
This emergence coincides with apparent community transmission reported in several European countries, including Spain, Italy, the Netherlands, and Portugal, alongside the continued presence of the older variant globally. Globally, there have been more than 44,000 reported cases of mpox in 2025 – surpassing the total reported in 2024.
Factors Contributing to the Challenge
Several factors complicate efforts to track and control the spread of the new variant. Vaccination, while beneficial for individual protection, can lead to less severe symptoms, making passive surveillance more difficult. Researchers estimate that in Los Angeles, only about one in 33 cases of the older mpox variant is currently being detected, highlighting a significant underreporting issue.
Furthermore, the virus has adapted to infect men and women at roughly the same rate, a departure from the pattern seen in the 2022 outbreak, which disproportionately affected men who have sex with men. “Dense sexual networks,” characterized by multiple sexual partners, appear to be a key factor in transmission, though drawing parallels from the Democratic Republic of the Congo to other countries remains challenging.
Community Response and Public Health Strategies
In response to these challenges, public health officials are advocating for more proactive case-finding and monitoring strategies, including wastewater sampling to identify spread. Experts emphasize the critical role of community-based organizations in providing information, reducing stigma, and encouraging testing, as demonstrated during the 2022 outbreak.
Public health messaging continues to focus on vaccination, which is widely considered a valuable tool for individual protection. Making vaccines readily accessible, especially in underserved communities, through government-provided access and convenient locations, is vital.
The challenges are compounded by budget cuts and staff reductions within the US public health system, impacting surveillance networks and hindering response efforts. These issues are occurring against a backdrop of the US government being largely shut down, further limiting capacity.
“Really, we benefited from community-based organizations providing information and going out and trying to reduce that stigma,” said Jason Kindrachuk, an international expert on mpox.
The emergence of this new mpox variant underscores the need for ongoing vigilance, adaptive public health strategies, and strong community partnerships to effectively control its spread.
