'Mpox has not disappeared': Why the infectious disease is still spreading in the US and may be here to stay

Mpox, formerly known as monkeypox, has resurfaced in the United States despite initial hopes that the disease had subsided. The virus, which first emerged in 2022, has continued to circulate, with recent reports indicating that it may become endemic in the US. Sporadic cases have been observed since the 2022 outbreak, but now 2,800 cases have been reported in 2024 and over 2,500 in 2025, with only a small fraction linked to travel.

The mpox virus has established itself in the US, persisting year after year, according to Ryan Standford, an epidemiologist at the CDC's Poxvirus and Rabies Branch. While the exact threshold for endemicity remains undefined, each passing year provides evidence of this transition. The virus' ability to persist at low numbers across the entire country is still a mystery, though experts speculate that low vaccination rates may be a contributing factor.

To combat the spread of mpox, a two-dose JYNNEOS vaccine is required, which is 66% to 90% effective. However, vaccination rates among at-risk populations remain low. In the US, mpox primarily affects men who have sex with men, and public health efforts have largely focused on this group. Experts suggest that sustained public health efforts are crucial to eliminating the disease from the country.

Certain factors, such as insufficient vaccination and an understanding of the virus' transmission dynamics, may be responsible for the continued circulation of mpox. Men who have sex with men are at increased risk due to the outbreak's initial appearance within a specific sexual network. The virus has exploited the same transmission network that HIV had previously explored, resulting in densely connected clusters of infection.

Once individuals within this network gain immunity through infection or vaccination, the cases fade, creating the persistent trickle of cases observed today.

In summary, mpox has not disappeared from the US and may become endemic due to factors such as inadequate vaccination rates and the virus' persistence within an established transmission network. To combat the spread of mpox, sustained public health efforts and widespread vaccination are essential.