Mpox is spreading inside the U.S. now. Here's who the vaccine is for.
More than 90 clade I mpox cases have been reported across at least 23 states and Puerto Rico, with local transmission since August; here is how the rash shows up, who qualifies for the two-dose vaccine, and when a new bump needs a test.
On Tuesday, October 20, the Southern Nevada Health District reported the first clade I mpox case in a Clark County resident. The person had no recent travel exposure, never needed a hospital, and has recovered. 1
The same district has logged 11 clade II cases since August, so both clades are now circulating in Las Vegas. 1
Las Vegas is the newest stop for something that now spreads inside the country. Since November 2024, the CDC has counted more than 90 laboratory-confirmed clade I cases across at least 23 states plus Puerto Rico. 2
The part that changed is how people caught it. Earlier this year, many cases came from travel or from sex with someone who had traveled. Since August, a growing share had neither. 2
CDC now describes a likely shift toward ongoing clade Ib spread inside the United States. It still rates the risk to most people here as low, and low to moderate for men who have sex with men. 3
What the word "clade" changes
Mpox comes in two clades. Clade II caused the 2022 outbreak, which reached more than 100,000 cases across 120-plus countries and still circulates at low levels. 2
Clade Ib is the one spreading now. It emerged in eastern DR Congo in late 2023, moved through Central and Eastern Africa, and has since turned up in travelers on every continent. 3
Both clades spread the same way and are prevented the same way. 2
Here is the shortcut that used to work: with no trip abroad and no partner who had been away, mpox belonged to somebody else. Domestic transmission closes that shortcut. 2
The numbers
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What it actually looks like
Symptoms usually start within 21 days of contact, and that stretch is silent — you feel fine and have no way to tell. 4
Most people get a flu-like phase first: fever, chills, swollen lymph nodes, headache, muscle aches, exhaustion, sometimes a sore throat or cough. The rash arrives a day to four days later. 4
It begins as flat spots, turns into pimples or blisters, then crusts into scabs. It can hurt or itch. 4
Places to expect it: hands, feet, chest, face, mouth, and the skin around the genitals or anus. 4
Some people get the rash with none of the flu symptoms, which makes the rash itself the thing worth knowing. 5
Illness usually runs two to four weeks. 5
You can pass it on from your first symptom until the last scab has fallen off and fresh skin has closed over the spot. 4
How it moves
Close, sustained skin-to-skin contact does most of the work: sex, kissing, cuddling, massage. 6
Shared towels, bedding, clothing, cups and sex toys carry it too if someone with the rash used them. 6
Condoms cut exposure to the skin they cover. The rash can also sit on hands, chest, thighs or face, so a condom handles the part of the skin it reaches. 6
That is why cases cluster in sexual networks and households. 2
Who the vaccine is for
JYNNEOS is a two-dose vaccine built for mpox and smallpox, and CDC expects it to protect against both clades. 2
The doses sit 28 days apart. If you blow past that date, get the second one late; the series still counts. 7
Protection is strongest about two weeks after dose two. One dose helps, and two is what the recommendation is built on. 7
CDC recommends it if:
- You had known or suspected exposure to someone with mpox. 7
- You had a sex partner in the past two weeks who was diagnosed with mpox. 7
- You are a gay, bisexual or other man who has sex with men, or you are transgender or nonbinary, and in the past six months you had a new STI diagnosis, more than one sex partner, sex at a commercial sex venue, or sex tied to a large event or an area where mpox is spreading. 7
- Your partner has any of those risks, or you expect to be in one of those situations. 7
- You are traveling to a country with a clade I outbreak and plan new partners, commercial sex, sex in exchange for money or goods, or sex around a big event. 7
Where to get it: health departments, some pharmacies, clinics and hospitals. In smaller cities the health department is often the only door. 7
Cost depends on the clinic, and some insurance plans cover the shot. 7
If you had a known exposure, go now. The vaccine works best within four days and can still soften the illness up to 14 days after. 6
If you find a bump
Testing is a swab rubbed firmly across more than one lesion, then a PCR test. 8
Tests run through public health departments are usually free. 8
Call the clinic before you walk in, so staff can protect themselves and the waiting room. 1
Leave the lesions alone. Popping one moves virus onto your own skin, slows healing and opens the door for bacteria. 9
Cover the rash with gauze, wear a mask around people, keep your towels and bedding to yourself, and wash your hands after touching anything near a sore. 9
Isolation ends when the last scab falls off and new skin forms underneath. 5
Tell the people you had sex with, live with, or spent long stretches of skin contact with. Their window for protective vaccination is 14 days. 9
Ask a friend in another home to take your pet until you are clear. 9
Where home care ends
Most people get through this with rest, fluids and pain relief, on a two-to-four-week calendar. 9
Call a provider for pain you cannot manage, a rash in or near your eyes, sores in your mouth or throat that make drinking hard, or a rash spreading over a lot of skin. 9
Severe illness is likelier with uncontrolled HIV, some cancers and transplants, immune-suppressing drugs, active eczema or psoriasis, and pregnancy. 9
Two randomized trials — PALM007 for clade I in DR Congo, STOMP for clade II — found tecovirimat safe and no faster at clearing lesions. That is why rest and pain control carry most cases. 10
That drug stays available through an expanded-access program for people who are severely ill or at high risk of getting there. 10
For a local signal, CDC's wastewater dashboard tests sewage for both clades at hundreds of sites and updates every Friday. 11
The short version
- Clade I mpox has passed 90 U.S. cases in at least 23 states plus Puerto Rico, and since August some carry no travel link. 2
- Both clades move through sustained skin-to-skin contact, including sex and shared bedding. 6
- JYNNEOS is two doses, 28 days apart, and CDC's eligibility list needs a risk group plus a specific behaviour in the past six months. 7
- A new bump alongside fever or swollen lymph nodes is worth a swab, and public health testing is usually free. 8
- Most cases clear in two to four weeks; eye, airway and hard-to-manage pain symptoms need a provider fast. 9
References
- 1Health District reports first clade I mpox case in Clark County resident — Southern Nevada Health District
southernnevadahealthdistrict.org
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- 5Public Health Advisory: Mpox Clade Ib Detected in Clark County, NV — Southern Nevada Health District
media.southernnevadahealthdistrict.org
- 6Preventing Monkeypox — CDC
cdc.gov
- 7Monkeypox Vaccination — CDC
cdc.gov
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