California has detected the first case in the country of a new strain of mpox spreading from person to person. The infected person had recently traveled from East Africa, where many countries are struggling with the transmission of this virus.

The individual was being treated at a healthcare facility in San Mateo County and is being isolated at home, the California Department of Public Health said in a statement released Saturday. In a separate statement, the Centers for Disease Control and Prevention said the person was not currently being treated with anti-mpox medication, which could be a sign that the infection was mild.

The version of the virus with which the person is infected is known as clade Ib, a branch of clade I viruses that has traditionally spread to humans from an animal source in countries in East Africa where the virus lives in nature. It is different from the clad IIb virus responsible for the major international mpox epidemic that began in 2022.

California health officials said there is currently no evidence that the infected person transmitted the virus to anyone else.

“Public health workers are contacting individuals who were in close contact with this individual, but there is no concern or evidence that mpox class I is currently spreading among individuals in California or the United States,” the statement said.

The World Health Organization has declared ongoing human-to-human spread of mpox. Public Health Emergency of International Concern in August. The 2022 outbreak was also declared as PHEIC.

Samples from the California case were sent to the CDC for further analysis.

Person-to-person spread of Clade Ib viruses was first detected in the Democratic Republic of Congo in September 2023. While most transmission of this virus occurs in African countries, travel-related cases have been identified in Germany, India, Kenya, Sweden, Thailand, Zimbabwe, the United Kingdom and now the United States.

The CDC said it currently considers the risk to the U.S. population from the clade Ib outbreak in Central and East Africa to be low. simulation exercises ran.

“These simulations indicate that transmission through close contact within and between households is unlikely to lead to large numbers of mpox clade I cases in the United States,” the statement said. “There has also been no significant onward spread of the virus in Sweden, Thailand, Germany and India, and spread in the UK has so far been limited to close household contacts.

More than 115,000 cases of mpox, both class I and class II, have been reported by at least 123 countries so far this year. At least 255 of these infections were fatal. a database It is maintained by WHO.

Mpox virus is related to smallpox, a disfiguring and often fatal virus that was declared eradicated in 1980. (Smallpox is the only human virus that has been eradicated.) Like smallpox, mpox triggers a blistering rash that leaves scars. It can also be fatal, but the case fatality rate is significantly lower than the mortality rate due to smallpox.

Historically, most cases were thought to be transmitted by someone (mostly children or hunters) who came into contact with infected animals in parts of Africa where the viruses were found. There was occasionally spread of the disease from an infected person in this way, from a family member or healthcare worker who came into contact with the infected person’s lesions, or from contact with contaminated bedding.

However, since 2022 it has been clear that viruses are sexually transmitted, and it has been that way for some time. The Clade IIb epidemic resulted largely from transmission in communities of gay, bisexual, and other men who have sex with men. Clade Ib transmission has been associated with men who have sex with men, but also with sex workers and their clients and their household contacts. There are vaccines that protect against mpox, primarily the Bavarian Scandinavian Jynneos vaccine. However, global production of these products is limited.