CNN
—

The first known case of a more severe form of MPOX in the United States was confirmed in California, the U.S. Centers for Disease Control and Prevention said Saturday. The risk from clade I mpox to the public remains low, the agency said.

The individual diagnosed with clade I mpox had recently traveled from East Africa, where an mpox outbreak is ongoing. The person was treated at a local medical facility and released, the CDC said. The person is isolated at home and their symptoms are improving. The state and the CDC are working to identify and follow up on potential contacts.

Clade II mpox has been circulating in the United States since a major outbreak in 2022 and 2023. A more recent outbreak in Africa is caused by clade I, which is known to cause more severe disease.

The subtype responsible for most of the continued spread, clade Ib, is relatively new. Travel-related cases of mpox clade Ib have been reported in Germany, India, Kenya, Sweden, Thailand, Zimbabwe and the United Kingdom. Some countries outside Africa have also reported locally transmitted cases.

“The recent travel-related clade I mpox cases outside Africa have all been attributed to subclade Ib; there have been no deaths associated with these cases and available data for a subset provide detailed disease progression,” the CDC said Saturday.

“Historically, clade I mpox has caused more severe illness and deaths than clade II mpox; However, recent data indicate that infections by clade I mpox in the current outbreak may not be as clinically severe as in previous outbreaks. While outbreaks of clade I mpox had mortality rates around 3%-11%, more recent outbreaks had mortality rates of only about 1% when patients received good medical supervision and supportive clinical care. Death rates are expected to be much lower in countries with stronger healthcare systems and treatment options, including the United States.”

The World Health Organization says the number of MPOX cases has been rising in Africa, driven mainly by cases in the Democratic Republic of Congo, Burundi and Uganda. On November 22, WHO will convene a meeting of its Emergency Committee on MPox to advise whether the current outbreak continues to constitute a public health emergency of international concern.

Mpox, formerly known as monkeypox, is a viral disease related to the now eradicated smallpox virus. According to the WHO, the disease can spread through close contact, such as touching, kissing or sex, as well as through contaminated materials such as sheets, clothing and needles.

The first symptoms are usually flu-like – including fever, chills, exhaustion, headache and muscle weakness – often followed by a painful or itchy rash with raised lesions that crust over and disappear over a period of weeks.

The CDC says people can protect themselves from MPox by avoiding contact with people with symptoms and contaminated materials such as clothing, bedding, sex toys and toothbrushes. Eligible people are recommended to receive two doses of MPOX vaccine.