#18,912
While the threat from an emerging Clade Ib Mpox virus was announced more than a year (see Aug 2024's WHO Declares Mpox A PHEIC), most of cases reported outside of Africa have been come from Europe, and only a few appear to be locally acquired.Four days ago (Oct 14th), however, the city of Long Beach, in L.A. County, confirmed its First Case of Clade I Mpox which was also the first case in the United States without known international travel.
Long Beach, CA – The Long Beach Department of Health and Human Services (Health Department), in coordination with the California Department of Public Health (CDPH), has confirmed a case of clade I mpox (previously known as monkeypox) in a Long Beach resident with no recent travel history. This is the first case of clade I mpox in Long Beach, the seventh case nationally and the first without known travel. The person required hospitalization and is now isolating and recovering at home.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.
In their most recent risk assessment (Oct 2025), the WHO writes:
The mortality associated with clade Ib MPXV outbreaks generally remains lower (less than 1% where large outbreaks have been reported) than what has been historically reported for clade Ia MPXV-endemic provinces in DRC, and broadly comparable to what has been observed during the global clade IIb MPXV outbreak.
As observed with other subclades, MPXV can be particularly severe among immunocompromised individuals, such as those living with uncontrolled HIV infection, as observed in countries such as Uganda and Sierra Leone. This is especially concerning in sexual networks where HIV prevalence may be high and access to HIV prevention and care services remains limited, especially with reduced funding for HIV control programmes in some of the affected countries.
Tuesday's announcement was followed on Thursday (Oct 16) by a second press release - this time from the L.A. County Health Department - on a 2nd local case without international travel.
October 16, 2025
County Public Health Confirms Its First Case of Clade I Mpox - Case not linked to travel; Public health urges vaccination, testing, and prevention.
The Los Angeles County Department of Public Health has confirmed its first case of clade I mpox in an adult with no recent travel to regions where this virus is typically found. The individual was hospitalized and is now recovering at home.
This is the second clade I mpox case in LA County and the second in the nation without known travel to another country where clade I is typically found. The City of Long Beach, which has its own health department, also announced a separate clade I mpox case earlier this week.
Public Health is collaborating closely with California Department of Public Health and the U.S. Centers for Disease Control and Prevention to investigate these mpox cases as swiftly and effectively as possible. Enhanced surveillance and contact tracing are underway to identify any additional cases and potential sources of the infection and to prevent further transmission.
Just twenty-four hours later (yesterday, October 17th) L.A. County announced a 3rd locally acquired case.
October 17, 2025
County Public Health Investigating Possible Local Spread of Clade I Mpox After Third Case Confirmed in Los Angeles County - Third case also with no recent travel
The Los Angeles County Department of Public Health is investigating the possibility of a local spread of Clade I mpox cases after confirming its second case in an adult with no recent travel to regions where this virus is typically found. The individual was hospitalized and is now recovering at home.
This is the third clade I mpox case in LA County and the third in the nation without known travel to another country where clade I is typically found. Public Health announced its first case yesterday and, earlier this week, the City of Long Beach, which has its own health department, announced its first case. At this time, no clear link has been identified between the cases.
Public Health continues collaborating closely with California Department of Public Health and the U.S. Centers for Disease Control and Prevention (CDC) to investigate these mpox cases as swiftly and effectively as possible. Enhanced surveillance and contact tracing are underway to identify any additional cases and potential sources of the infection and to prevent further transmission. The CDC is conducting additional testing to identify the virus’s genes (genomic sequencing) in each case.
There are a number of unanswered questions, including the onset/hospitalization dates of these cases, and details on their symptoms. All we know is all 3 cases were hospitalized and are now recovering at home, and `no clear link' has been established between cases.
While the risks to the general population are consider low, this is the first time we've seen local transmission in the United States, and so a larger outbreak is possible.
LA County Public Health is strongly urging `at risk' communities to get the JYNNEOS vaccine, to get tested if they have symptoms, and to practice `safer' sex.
Although the JYNNEOS vaccine is not 100% effective in preventing infection, and we've seen at least 3 studies suggesting its effectiveness may wane over time (see here, here, and here), it is still the most effective pharmaceutical option available.
Like all viruses, Monkeypox continues to evolve and diversify, as was discussed in the 2014 EID Journal article Genomic Variability of Monkeypox Virus among Humans, Democratic Republic of the Congo, where the authors cautioned:
Small genetic changes could favor adaptation to a human host, and this potential is greatest for pathogens with moderate transmission rates (such as MPXV) (40). The ability to spread rapidly and efficiently from human to human could enhance spread by travelers to new regions.
In the decade since study was published, 2 new clades (Ib and IIb) have emerged, and have spread outside of Africa.
While clade Ib has not gained much of a foothold outside of Africa over the past year, our collective immunity from the smallpox vaccine - which was discontinued in the late 1970s - continues to wane.
Which only increases the chances that another emerging pox virus will find a way to make a comeback.
Stay tuned.
