Ongoing 2022 Mpox Clade II Outbreak

Mpox in the United States

In May 2022, mpox cases were reported in previously unseen numbers in areas where mpox didn’t regularly occur. An unprecedented global mpox outbreak followed.

There are two types of mpox, clade I and clade II. The ongoing global outbreak has been caused by clade II.

Digitally colorized blue and red electron microscopic image depicting virus particles from a human skin sample

In the United States, case numbers peaked in early August 2022. By the end of the first year of the outbreak, more than 30,000 U.S. mpox clade II cases were reported and more than 140,000 specimens of suspected mpox were tested.[1]

Two years later, many things are different in the United States:

Clade II mpox is still circulating, but at much lower levels, mostly in small clusters in urban areas.
We are able to quickly test for mpox at laboratories nationwide, and we have expanded monitoring for mpox in wastewater in communities across the country.
We have an ongoing clinical trial to learn more about the effectiveness of TPOXX for treatment of mpox.
And we have ample supplies of mpox vaccine – anyone who is eligible can get the recommended two doses.

But some things remain the same: in the United States, clade II mpox is still mostly being spread through sexual and intimate contact, and gay, bisexual, and other men who have sex with men are at the highest risk of getting mpox. For the second summer in a row, CDC is closely working with the Department of Health and Human Services’ Summer of Pride initiative to help health departments and community organizations provide comprehensive sexual health services, including mpox vaccination, at local Pride and LGBTQ+ community events.

We’re hopeful there won’t be an increase in mpox cases this summer, as there wasn’t one last summer. But because mpox is still spreading in the United States, it’s important for people to know the latest, and know how to protect themselves so they can enjoy their summer. Here’s what we know about mpox in the United States right now.

The number of illnesses reported recently is far below the peak of the outbreak in July and August 2022, when the national 7-day average was more than 450 cases a day (or more than 11,000 per month). Between January and September 2023, there were fewer than 180 cases reported per month. In October 2023, there was an uptick to about 250 that month. Case counts have remained consistent at about 250 a month since then.
In 2023, there were a total of 1,700 cases. So far in 2024, a total of 1,122 cases have been reported.
A new CDC study[2] indicates that getting two doses of mpox vaccine works to prevent mpox, yet only 23% of eligible people have received the vaccine. It’s very rare for people to get mpox after they’ve been fully vaccinated.
Most new mpox cases continue to be in people at higher risk for mpox who were not vaccinated with JYNNEOS.[3]
Wondering about boosters? The same CDC study[4] suggests that people who have received both doses do not need booster doses at this time. There have been a small number of infections in people who have been vaccinated, but vaccination is likely to make the infection milder and reduce the risk of severe infection and death.

The antiviral drug tecovirimat (TPOXX) has been used to treat mpox, especially people with severe mpox or who are likely to get severely ill. The safety and effectiveness of TPOXX are being evaluated through the STOMP clinical trial. If you know someone newly diagnosed with mpox, encourage them to join this trial to get access to TPOXX and help people in the future.

How CDC is helping during the ongoing outbreak

CDC has continued to work with key partners to get the word out about vaccinating and reducing mpox risk. In partnership with the CDC Foundation, CDC has done critical work to support vaccine uptake among the communities disproportionately affected by mpox, including the LGBTQ+ community. Approximately $5 million was awarded to support 42 community-based organizations working to increase mpox vaccine confidence, access, and acceptance. Recently, the CDC Foundation teamed up with an icon of the LGBTQ+ community, Dashaun Wesley, to produce social media videos highlighting the importance of getting both doses of the vaccine to protect against mpox.

CDC also continues to support state and local health departments efforts, including sustained work from a previously awarded $46.2 million to 62 jurisdictions to increase mpox vaccine accessibility, demand, and uptake. These funds have also been used to strengthen the capacity of health departments to conduct mpox surveillance and testing, and for prevention campaigns.

CDC is committed to health equity and ensuring that the populations most affected by mpox have access to the mpox vaccine. We’ve funded studies to better understand why people decide to get vaccinated against mpox or not. Partner organizations, including the National Coalition of STD Directors and National Coalition for Sexual Health, have leveraged this research to develop equity-centered and free communications materials and a communication toolkit.

Mpox in the Democratic Republic of the Congo

Right now, the Democratic Republic of the Congo (DRC) is experiencing the highest number of suspected mpox cases on record in that country, with more than 22,000 suspected cases and more than 1,000 deaths. The clade of mpox virus that causes cases in DRC (clade I) is associated with a higher rate of severe disease than the clade that caused the ongoing global outbreak that began in 2022 (clade II).

No cases of clade I mpox have been reported in the United States at this time.

CDC has been working on mpox with partners in DRC for more than a decade. We’re now assisting DRC and several bordering countries as part of a broader effort composed of nine U.S. government departments and agencies. [5] This U.S. government mpox response team is working to help control this outbreak and prepare for any cases that might reach the United States. In DRC, CDC has helped set up additional laboratory testing, deliver testing materials, and train staff to build and enhance laboratory capacity, and we’ve worked with our DRC colleagues to analyze case data to identify how mpox is spreading. CDC has trained field epidemiologists to detect cases and trace and monitor contacts in priority health zones, and we’ve provided technical assistance and funding to the DRC Ministry of Health and in-country organizations to strengthen the local response. The US government response team is in ongoing discussions about mpox vaccine donation and additional support for treatment and surveillance.

Based on CDC assessments, the anticipated risk of mpox spreading from the DRC outbreak to the U.S. general population is very low. Nevertheless, it’s important to be ready domestically. Because of the mpox outbreak that began in 2022, the U.S. has the tools needed (diagnostics, vaccines, and therapeutics) to respond to clade I mpox if the virus begins to circulate here.

CDC issued an advisory for U.S. clinicians to be aware of the possibility for mpox in travelers who recently have been to DRC, and alerted travelers to and from the DRC to be aware of mpox symptoms and to seek immediate medical attention if a new, unexplained skin rash develops. We have increased domestic surveillance efforts and continue to expand CDC diagnostic testing capacity. CDC continues to engage with our public health partners, key organizations representing communities at potentially increased risk for clade I mpox, and other U.S. government agencies.

The heart of the matter

Based on what we know, people in the United States who have already had mpox or have had both doses of mpox vaccine are likely to be protected against clade I mpox.

We want to get the word out: If people are eligible for the mpox vaccine, they should get vaccinated!

If they are a gay, bisexual, or other man who has sex with men, or if they’re transgender, gender non-binary, or gender-diverse AND have other sexual risk factors, they’re eligible.
They should get two doses of JYNNEOS 4 weeks apart.
Even if it’s been longer than 4 weeks since the first vaccine dose, they should get the second dose as soon as possible.
If they’ve already been diagnosed with mpox, they don’t need the vaccine.

They can find out where to get the mpox vaccine at cdc.gov/mpox.

Two men with bandages on their arms from getting the mpox vaccine at a 2022 vaccine event

During the past two years, sexual behavior changes by populations at higher risk helped reduce mpox transmission. If people are at risk for mpox but haven’t gotten both doses of the vaccine yet, they should consider temporarily changing activities that involve close personal contact, including sex. Or if they’re at a rave, party, or club where there is direct, personal, skin-to-skin contact, avoid any rash they see on others. If they or a sexual partner has or recently had mpox symptoms, or they have a new or unexplained rash anywhere on their body, don’t have sex and see a healthcare provider. In some cases, symptoms may be mild, and people may not even know they have mpox.

If they or a partner has mpox or think they may have mpox, the best way to protect themselves and others is to avoid sex of any kind (oral, anal, vaginal) and kissing or touching each other’s bodies while they’re sick. They should especially avoid touching any rash. They also shouldn’t share things like towels, fetish gear, sex toys, and toothbrushes. Everyone can learn more about Safer Sex, Social Gatherings, and Mpox.

Mpox isn’t new, and we have the tools, vaccine, and knowledge to prevent infection – and suffering. This summer and beyond, we can work together to stop the spread of mpox.

The bottom line

Mpox is still circulating at low levels in the United States, mostly in small clusters.
Case numbers have remained consistent since October 2023.
Everyone who is eligible for the mpox vaccine JYNNEOS should receive two doses, four weeks apart.
Getting two doses of JYNNEOS works to prevent mpox. It’s very rare for people to get mpox after they’ve been fully vaccinated.
Most new mpox cases continue to be in people who were not vaccinated with JYNNEOS.
CDC is committed to health equity and ensuring that the populations most affected by mpox have access to the mpox vaccine.
People at risk should continue to practice safer sex and avoid touching any kind of rash on others.
If someone is diagnosed with mpox, consider joining the STOMP clinical trial to get access to TPOXX, an antiviral medicine that’s been used to treat mpox in the United States.
There are two kinds of mpox, clade I and clade II. Clade II caused the global outbreak that started in 2022. There is a clade I mpox outbreak occurring in the Democratic Republic of the Congo (DRC), but no cases have been reported in the United States.
CDC is working with other U.S. government agencies, international agencies, and DRC government agencies to help slow the clade I outbreak.
There have been no cases of clade I mpox reported in the United States, and the risk of it spreading in the U.S. general population is very low.
CDC is working with state, local, county, territorial, and tribal health departments to prepare and be ready just in case clade I mpox is ever reported in the United States.

Resources

[1] The CDC Domestic Mpox Response — United States, 2022–2023 [PDF - 6 pages]

[2] Monkeypox Virus Infections After 2 Preexposure Doses of JYNNEOS Vaccine — United States, May 2022–May 2024

[3] Monkeypox Virus Infections After 2 Preexposure Doses of JYNNEOS Vaccine — United States, May 2022–May 2024

[4] Monkeypox Virus Infections After 2 Preexposure Doses of JYNNEOS Vaccine — United States, May 2022–May 2024

[5] U.S. Preparedness and Response to Increasing Clade I Mpox Cases in the Democratic Republic of the Congo — United States, 2024 | MMWR (cdc.gov)