Mpox cases, symptoms, how it spreads: What to know after first case of clade I reported in US

The first case of mpox clade I was found in California, but the risk to the public remains low, public health officials said Saturday.

There are two types of mpox, clade I and clade II, according to the Center for Disease Control. Each type has its own subclade that have "different characteristics, like who they affect, how they're spread, or even how many deaths they cause."

However, the case that was announced on Saturday is the first of the clade I strain to be found in the country.

The person with the virus had recently returned to California after traveling to eastern Africa, where the strain (clade I mpox) has affected several countries, the Centers for Disease Control and Prevention said in a news release. State and federal health officials said the risk to the public from this first U.S. case is low.

The person is in isolation, and people who were in contact with them are being contacted by health officials, Paste BN previously reported. Here's what to know about mpox, formerly known as monkeypox.

Mpox cases in the US, around the world

While this the first case of clade I to be announced in the U.S., 3,004 cases of mpox clade II have been recorded since Jan. 1, 2024, according to CDC data.

The U.S. case count of mpox comprises roughly 14% of the total cases of clade I and II reported globally this year (21,370), per the CDC, while 11,911 cases have been reported in countries with only clade I mpox.

There is no evidence that the mpox clade I strain is spreading between people in California or elsewhere in the U.S., according to state health officials.

Mpox symptoms

Clade I has historically led to more severe illness compared to clade II, the strain associated with other U.S. cases of mpox. California health officials said recent infections indicate the clade I strain may not be as clinically severe compared to previous outbreaks, especially when people have access to quality medical care.

The following are symptoms for mpox, according to the World Health Organization:

• Painful rash with sores
• Enlarged lymph nodes
• Fever
• Headache
• Muscle ache
• Back pain

How does it spread?

Mpox, which comes from the same virus family as smallpox, spreads from animals to people, and it received its former name, monkeypox, because that is the animal it was first discovered in.

The virus spreads among humans through close contact and exposure that includes, but is not limited to, the following, according to the WHO:

• Sexual contact
• Bodily fluids
• Lesions on the skin or area like the mouth or throat
• Respiratory particles
• Contaminated objects

How to prevent the spread

People can take the following measure to prevent the spread, according to the CDC:

• Avoid close contacts with individuals infected with the virus, including people with skin or genital lesions
• Don't come in contact with things touched by people infected with the virus, like clothing, bedding, toothbrushes, sex toys, or objects and materials used in healthcare settings
• Receive both recommended doses of the mpox vaccine

Julia is a trending reporter for Paste BN. You can connect with her on LinkedIn, follow her on X, formerly known as Twitter, Instagram and TikTok: @juliamariegz, or email her at jgomez@gannett.com