The Centers for Disease Control and Prevention (CDC) warned that a more infectious mpox virus strain has been found in the Democratic Republic of the Congo.

The CDC said the new strain, Clade I MPXV, has not been detected in the United States, but clinicians should be aware of the strain for people who have traveled to Congo.

The agency issued a travel health notice to people traveling to the DRC and said that people who recently traveled there should seek medical care if they develop a “new, unexplained skin rash,” or lesions, with or without fever and chills.

Congo has reported 12,569 suspected mpox cases since the start of the year, a substantial increase from the 3,767 cases seen annually in the past, the CDC said. The outbreak is in 22 out of the country’s 26 provinces, including urban areas.

The CDC listed the outbreak as a level two advisory, warning people to “practice enhanced precautions,” including not touching live or dead animals, avoiding eating or preparing wild game and to stay away from infected people and their belongings.

There is an mpox vaccine available, but the CDC said the vaccination rate in the U.S. remain low. Only 1 in 4 people who are eligible to receive the vaccine have received both doses.

The mpox virus quickly spread last year throughout the United States and other countries around the world in vulnerable populations, particularly among men who have sex with men — though health officials have stressed the virus doesn’t discriminate. Health officials urged gay and bisexual men to take precautions to stay safe. The World Health Organization deemed mpox no longer a global heath emergency in May.

The virus has previously been associated with human-to-human contact, but the CDC said it has also been found in non-sexual routes of transmission.

Mpox has been endemic in parts of central and west Africa for decades, where it made its way to humans from infected rodents and caused limited outbreaks. Symptoms often include fever, rash, headache, muscle aches and swollen lymph nodes.

— Updated at 2:54 p.m.