Arizona confirms first case of deadlier mpox strain; 'risk to public is low'

The Clade I strain of mpox is known to cause more serious illness and has higher death rates than the more common Clade II strain. Clade I is, to date, far rarer in the United States than Clade II mpox, which has been circulating in the country since 2022.

The Arizona Department of Health Services said the risk to the general public is low and there's no evidence that Clade I mpox is spreading in Arizona.

According to the U.S. Centers for Disease Control and Prevention, the risk posed by the Clade I mpox outbreak to most people remains low. The risk to men who have sex with men is low to moderate, the federal agency says.

Federal health officials said that as of June 2026 there had been at least 20 Clade I mpox cases reported in the United States and that the incidence of the cases began to increase in frequency at the beginning of March 2026.

Mpox, formerly known as monkeypox, is a viral infection similar to smallpox that typically causes painful rashes with sores and blisters and swollen lymph nodes, and it typically spreads through skin-to-skin contact with the sores, blisters and body fluids.

Other ways the virus can spread include: from infected animals; from sharing bedding, towels, clothing or other personal items; and prolonged close contact with someone who has mpox. The virus can pass to a baby during pregnancy, state health officials said, and casual contact in places such as stores, offices, or airplanes is unlikely to spread mpox.

State not providing details about Arizona patient

Citing patient privacy, the Arizona Department of Health Services would not disclose the age or gender of the person who was infected, nor would they disclose the county where the infected person resides, or if the person had been hospitalized.

They also did not say whether the case was subclade Ia or Ib. The CDC as of June 2 was reporting that recent travel-associated Clade I mpox cases have almost exclusively been attributed to subclade Ib and that there have been no deaths associated with the cases.

While the robust health care system in the United States has been able to treat people with Clade I mpox, globally it has proven more deadly, according to the CDC, with more than 55,000 confirmed cases since January 2024, including more than 150 deaths.

As of July 21 there had been 34 cases of mpox reported to the state: 32 in Maricopa County, one in Cochise County and one in Yavapai County, state data shows.

"We are monitoring them closely to better understand potential differences between Clade I and II," a news release from the Arizona Department of Health Services says. "Both types of mpox cause similar symptoms and we currently recommend using the same prevention measures including testing, vaccination, clinical management, and public health response."

A global outbreak of the less severe Clade II strain of mpox began in 2022 and continues to this day, including in some African countries, according to the World Health Organization. Growing outbreaks of subclades Ia and Ib have also been affecting the Democratic Republic of the Congo and other countries in Africa, the WHO says.

Subclade Ib was first detected beyond Africa in 2024, according to the WHO.

Symptoms of mpox may include a new or unexplained rash that looks like pimples or blisters and may be painful or itchy. Some people may also experience fever, headache, muscle aches, swollen lymph nodes, chills, exhaustion, or respiratory symptoms, state and federal health officials say, and people with weakened immune systems may be at greater risk for severe illness.

Vaccine will help prevent mpox

Anyone who has had close physical contact with someone infected with mpox has an increased risk of contracting the disease and should get two doses of the JYNNEOS vaccine to both prevent infection and reduce the risk of severe illness.

You can get vaccinated after an exposure. Vaccination is most effective when given within four days of exposure but may still reduce illness when given within 14 days, the state health department says. Check for symptoms for 21 days after your last contact.

Anyone who develops symptoms should avoid close contact with others, isolate at home and contact a health provider for testing.

Individuals who are infected with mpox should stay home and away from other people until all sores have healed, scabs have fallen off, and a fresh layer of skin has formed. If you need to be around others, cover rashes or lesions with clothing, gloves or bandages, the state health department says.

Other tips for avoiding the spread:

Do not have sex or close physical contact if you or your partner has a new or unexplained rash, sores, or other symptoms of mpox.

Condoms may reduce exposure in some areas of the body but may not prevent all mpox exposures because sores can appear elsewhere on the body.

Consider reducing your number of partners.