The US Centers for Disease Control and Prevention urged doctors and health departments Thursday to be on the lookout for a more infectious strain of the virus that causes mpox, which is spreading in the Democratic Republic of Congo.
The agency has also issued a Travel Health Notice urging people who go to DRC to minimize contact with others who are ill, to steer clear of wild animals and to refrain from eating or preparing wild game.
The clade I monkeypox virus is more contagious and causes infections that are more severe than the clade II strain that was associated with the 2022-23 global outbreak, which has predominantly affected gay and bisexual men and other men who have sex with men, according to the CDC.
A clade is a broad grouping of viruses that has evolved over decades and is a genetic and clinically distinct group. Mpox is characterized by two distinct genetic clades.
No cases of clade I have been reported in the United States, the CDC stressed, but that strain is being spread through sexually associated human-to-human contact in DRC.
“Clinicians should continue to consider mpox when evaluating the cause of rashes,” the CDC said, noting that infection can look different from person to person.
“Mpox lesions may be small, firm and rubbery, deep-seated, and well-circumscribed, or they may be large, with diffuse, centrifugal lesion distribution,” the agency says.
Doctors should further investigate for mpox if a patient has swollen lymph nodes or has traveled to DRC within 21 days of illness. Public health officials are also being advised to enhance surveillance through testing should the strain be detected in the United States.
“Specimens collected from patients who traveled to DRC should be sent to CDC as expeditiously as possible,” the agency said in a news release. Laboratories should alert their state health department and the CDC if someone tests positive for clade I mpox.
Since January, DRC has reported more than 12,500 clinically diagnosed but not laboratory-confirmed mpox cases and nearly 600 suspected deaths from the virus, according to the agency.
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“This is a substantial increase from the median 3,767 suspected mpox cases reported annually in DRC during the years 2016-2021,” the CDC said.
More than 31,000 Americans were diagnosed with mpox in the 2022-23 outbreak, including 55 who died, according to CDC data.
There is a vaccine for mpox called Jynneos, but the CDC notes that vaccination coverage in the US is low because only 1 in 4 people who are eligible to get it have received both doses required for full protection.
According to the CDC, people at high risk for mpox include gay and bisexual men, other men who have sex with men, and transgender and nonbinary people who in the past six months have had at least one of the following: a new diagnosis of at least one sexually transmitted disease, more than one sex partner, sex at a commercial sex venue or in conjunction with a large public event in an area where mpox is spreading, sexual partners of people who have those risks and people who plan to participate in any of the previous activities.