A newer variant of mpox, the virus formerly known as monkeypox, is now spreading through some communities in the US and Europe.<\/p>\n
The risk to the general public is low, but community transmission in new places signals greater challenges for public health to detect cases and stop the spread.<\/p>\n
In October, California<\/a> announced three cases of the newer variant, known as clade Ib. All three of the patients \u2013 two in Los Angeles and one in Long Beach \u2013 were hospitalized and are now recovering.<\/p>\n None of the patients had apparent links to each other and none had traveled internationally recently, indicating the virus is likely spreading undetected in some communities. There have been six cases of the new mpox variant found among travelers in the US, but this is the first sign of community spread.<\/p>\n The news comes as several European countries \u2013 Spain, Italy, the Netherlands and Portugal \u2013 also report apparent community transmission of the newer variant, and the older variant continues to circulate globally.<\/p>\n There have been more than 44,000 cases of mpox reported so far in 2025, according<\/a> to the World Health Organization. That\u2019s more than the total reported in 2024.<\/p>\n The three cases in California appear may be linked genomically and may trace back to a travel case from August, according<\/a> to the American Hospital Association. The industry group said this information was released by the US Centers for Disease Control and Prevention (CDC) in an advisory on Wednesday, although that advisory does not appear to be available publicly.<\/p>\n The US Department of Health and Human Services did not respond by press time to the Guardian\u2019s media inquiry about potential genomic links between the cases and whether the virus appeared to be spreading in specific networks.<\/p>\n \u201cGiven that the three cases in Los Angeles were all hospitalized, that lends a little bit more credence to the idea that maybe there is local transmission going on,\u201d said Miguel Paredes, a genomic epidemiologist at the University of Washington.<\/p>\n In Los Angeles, about one in 33 cases of the older mpox variant is currently being detected, according to an October study<\/a>, co-authored by Paredes, which has not been peer-reviewed or published.<\/p>\n \u201cIf you\u2019re thinking about a 3% case fatality rate, and we\u2019re capturing the ones that are \u2018more severe\u2019, then we\u2019re not really capturing the ones that are potentially less severe,\u201d he said.<\/p>\n Vaccination may also complicate the picture.<\/p>\n \u201cVaccines are doing a good job of sometimes preventing infection but also creating less severe disease, which is good on an individual\u2019s side. But it also makes passive surveillance a little difficult, because if you have less severe disease, you\u2019re less likely to seek treatment or actually think you have mpox,\u201d Paredes said.<\/p>\n That means researchers and officials need to be more proactive about finding and monitoring cases, not just recording the cases of people who seek care, he said. Wastewater sampling would be one relatively inexpensive and unobtrusive way to monitor spread, he added.<\/p>\n In 2022, cases of the clade IIb mpox variant exploded internationally, infecting nearly 100,000 people around the world. About a third of the detected cases were in the US. The vast majority of those cases were among men who have sex with men.<\/p>\n Yet the new variant, which appears to have emerged in mid-2023 and was first detected in the Democratic Republic of the Congo, has not shown the same pattern. It has infected men and women, usually between the ages of 25 and 40, at roughly the same rate.<\/p>\n The outbreak in central and eastern Africa has spread through what Jason Kindrachuk calls \u201cdense sexual networks\u201d, or people with multiple sexual partners.<\/p>\n \u201cIt\u2019s a big piece of it,\u201d said Kindrachuk, who is an international expert on mpox and vice president of the National Microbiology Laboratory branch of the Public Health Agency of Canada.<\/p>\n \u201cDense sexual networks increased risk transmission generally. Regardless if you\u2019re male or female, you had an increased probability or increased risk of getting infected if you were within those networks.\u201d<\/p>\n But it\u2019s difficult to know if the same pattern would continue in other countries, he said. \u201cTrying to make assessments of what is going to happen in other regions of the world when you are looking at DRC or central Africa in general is very difficult.\u201d<\/p>\n There have only been a few community cases of the new variant detected internationally, so it\u2019s not possible yet to make broad statements about the kinds of networks where it is spreading, Kindrachuk said.<\/p>\n California has not released information about the gender or the sexuality of the patients. But the press release indicated<\/a> the newer variant was \u201cprimarily impacting communities of gay and bisexual men, and other men who have sex with men, as well as their social networks\u201d.<\/p>\n People are at higher risk for mpox if they are gay, bisexual, or a man who has sex with men, or are transgender or nonbinary, and have had more than one partner in the past six months, according<\/a> to the CDC.<\/p>\n