November 16, 2024
NR24-036

What You Need to Know: CDPH has reported to the Centers for Disease Control and Prevention (CDC) the first case of clade I mpox in the United States. Clade I is different than clade II, the strain of mpox that has been circulating in California and the United States since 2022. The individual is isolating at home and the risk to the public remains very low. 

SACRAMENTO – The California Department of Public Health (CDPH) has identified through laboratory testing the first known case of clade I mpox in the United States. This case was confirmed in an individual who recently traveled from Africa and is related to the ongoing outbreak of clade I mpox in Central and Eastern Africa. Historically, clade I has caused more severe illness than clade II, however, recent infections from clade I mpox may not be as clinically severe as in previous outbreaks, especially when cases have access to quality medical care.

The affected individual received health care in San Mateo County based on their travel history and symptoms. The individual is isolating at home and recovering. People who had close contact with this individual are being contacted by public health workers, but there is no concern or evidence that mpox clade I is currently spreading between individuals in California or the United States. 

The mpox specimens from the traveler ​are being sent to the CDC for further laboratory testing.  

Preventing Mpox Infection 

It appears clade I mpox spreads in a similar manner as clade II mpox, through close (skin-skin), intimate and sexual contact. The identification of a potentially more severe mpox version in the United States is a good reminder for individuals who have certain risk factors to take preventive action, including: 

• Getting vaccinated if you may be at risk for mpox. For the greatest protection, make sure you get both doses of the vaccine. Find mpox vaccine (JYNNEOS) near you.  
  
• Taking precautions if you were exposed to mpox. Get the mpox vaccine before symptoms develop and consider avoiding intimate contact with others for 21 days. Watch yourself for symptoms and get tested if they develop. 
  
• Preventing spread if you have been told you have mpox. Avoid contact with others until the rash is healed, clean and disinfect shared areas in the home, and notify people who may have been exposed. 
  
• Talking to your sexual partner(s).  
  
• Avoiding skin-to-skin contact with those who have a rash or sores that look like mpox. 
  
• Not sharing items with someone who has mpox. 
  
• Washing your hands often. 
  
• Protecting yourself when caring for someone with mpox by using masks, gowns and gloves. 

Mpox prevention information is also available on CDPH’s Sexual Health Toolkits and Campaign Materials Page . Casual contact, like one might have during travel, in an office, classroom or store, is unlikely to pose significant risks for transmission of mpox.

In late September, CDC issued enhanced precautions for travelers to countries in Central and Eastern Africa experiencing outbreaks.  

More information about mpox and clade I and clade II strains is available on the CDC website .  ​​