Mpox

Outbreaks

Updated: 3/13/2025

February 14, 2025: Since January 1, 2025, 12 people in New York City have tested positive for clade I mpox. (NYC Department of Health, accessed 3/13/25, https://www.nyc.gov/site/doh/health/health-topics/mpox.page)

February 7, 2025: A New Hampshire resident was diagnosed with clade I mpox after traveling to Eastern Africa, where there is an ongoing outbreak. The individual is self-isolating and recovering at home. The New Hampshire Department of Health and Human Services (DHHS) is investigating to identify close contacts, however, the risk to the public is low. (DHHS, accessed 3/13/25, https://www.dhhs.nh.gov/news-and-media/dhhs-identifies-new-hampshire-resident-clade-i-mpox)

January 2025: The Georgia Department of Public Health reported the second case of clade I mpox in the U.S. (CDC, accessed 5/15/25, https://www.cdc.gov/mpox/outbreaks/2023/)

November 18, 2024: California reported the first U.S. case of clade I mpox in a traveler returning from an area with ongoing transmission. The patient has mild illness and is recovering. Health officials are investigating potential contacts, but no additional cases have been detected as of November 18, 2024. The risk to the public remains low. (CDC, accessed 3/13/25, https://www.cdc.gov/han/2024/han00519.html)

Clade II mpox is still circulating at low levels in many countries around the world, including the United States. (CDC, accessed 3/13/25, https://www.cdc.gov/monkeypox/outbreaks/2022/index-1.html)

See the summary of the current Mpox situation in the United States and around the world.

See the summary of mpox cases and outbreaks that occurred in the United States before 2022.

About Mpox

Mpox is caused by the monkeypox virus (MPXV), an orthopoxvirus related to the variola virus, which causes smallpox. While less severe than smallpox, mpox can lead to significant illness, particularly in immunocompromised individuals. Mpox was first identified in 1958 in research monkeys, with the first human case reported in 1970 in the Democratic Republic of the Congo. Two genetic clades of MPXV have been identified: clade I (with subclades Ia and Ib) and clade II (with subclades IIa and IIb).

Clade II caused a multi-country outbreak in 2022-23 and has continued to spread at low levels worldwide. Clade I is responsible for recent outbreaks in Central and Eastern African countries, including Burundi, Central African Republic, Democratic Republic of the Congo, Republic of the Congo, Rwanda, and Uganda. See the list of countries affected by clade I mpox outbreaks.

Rodents and other small mammals are suspected to be the natural reservoir hosts of MPXV, but this has yet to be confirmed.

The virus primarily spreads through close, prolonged contact, including direct skin-to-skin contact with lesions, body fluids, or respiratory secretions of an infected person or animal. It can also spread through contact with contaminated materials such as bedding, clothing, or medical equipment. While MPXV can be transmitted through respiratory droplets, it does not spread as easily as smallpox or other airborne viruses. The incubation period ranges from 3 to 17 days, and an individual is considered contagious from the onset of symptoms until lesions have fully healed.

There are two FDA-approved vaccines, Jynneos and ACAM2000, for mpox prevention. Jynneos is a non-replicating vaccine recommended for those at higher risk of exposure, while ACAM2000 is a live-virus vaccine with broader availability but greater side effects. Tecovirimat (TPOXX) is an antiviral approved for treating smallpox and used under expanded access for severe mpox cases. Supportive care remains essential for managing symptoms and preventing complications.

Where to Start

See the CDC’s Mpox Webpage.
See the WHO's Disease Outbreak News (DONs)for the latest updates on recent outbreaks of Mpox.

Selected Resources

NETEC has curated essential Mpox resources. Many of these resources were developed at the beginning of the clade II outbreak but can be used for clade I patient management. However, diagnostic samples and clinical waste containing or contaminated with viral cultures of clade I MPXV are classified as Category A infectious substances and require different approaches to management and transportation. The resources below are marked to indicate whether they apply to clade I or clade II.

See below for clinical care and infection control resources related to Mpox, NETEC Resources and Other Resources, and for Waste Management Resources.

If you have questions or need support, you can submit a request via the website or by emailing info@netec.org, and one of NETEC’s experts in special pathogens will respond.