A person who recently travelled to Africa has become the first patient in the United States with a case tied to the new Clade I mpox outbreak. California’s state health department, the CDPH, confirmed the case. The patient is isolating at home.
Officials said the infection was linked to “the ongoing outbreak of Clade I mpox in Central and Eastern Africa.” Clade I is a different strain from Clade II, which has circulated in the U.S. since 2022.
How severe is Clade I?
Past Clade I outbreaks tended to cause more severe illness than Clade II. The CDPH offered a more cautious note on the current wave, saying that “recent infections from Clade I mpox may not be as clinically severe as in previous outbreaks.”
Mpox, which used to be called monkeypox, comes from a virus in the same family as smallpox. It is usually far less harmful. The disease first jumped from animals to people, and it now also spreads from person to person.
Symptoms and course
Fever, headaches, swellings, back pain and aching muscles come first. A rash may follow, and it can be extremely itchy or painful. Left alone, the infection can clear up within 14 to 21 days. Some cases have been fatal, particularly among vulnerable groups such as small children.
Where it came from
Mpox is most common in remote villages in the tropical rainforests of West and Central Africa, and countries such as the Democratic Republic of Congo have seen it for many years. Earlier this year an initial outbreak in DR Congo killed hundreds of people. The disease has since reached other parts of Central and East Africa.
Vaccines can help bring outbreaks under control by preventing infections. They are generally offered only to people at risk and to those who have been in close contact with someone infected.
