Officials said most patients are children ages 15 and younger and that low measles vaccine coverage and malnutrition may be contributing factors.
The test the US Centers for Disease Control and Prevention uses to identify clade I mpox cases is 'most likely not reliable' for detection of the substrain identified in the study, the authors say.
Another mpox study today showed that dose-sparing vaccine administration of the Jynneos vaccine appeared to have worked.
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Safety and immunogenicity profiles were similar to those seen in adult studies.
Health officials in the DRC are making progress with administering vaccine to high-risk people, as Nigeria expect to start its campaign next week.
Because not all viruses from mpox cases are sequenced, the findings likely underestimate the prevalence of the newly identified drug-resistant variant.
So far, more than 1,600 people have been vaccinated in some of the DRC's hot spots.
The CDC reports just 2 new measles cases, raising the national total this year to 264.
The most common changes made were reducing the number of sexual partners, avoiding group sex, and avoiding sex-on-premises venues.
The pledge came with at least $500 million in outbreak support, along with a plan to help bolster the domestic mpox vaccine supply.
Also, the CDC recommends that anyone anticipating sexual activity in the DR Congo and other affected countries receive 2 doses of mpox vaccine.
Vaccine-generated mpox antibodies largely waned after 6 to 12 months.
About 500 people in high risk groups in DRC-border regions have been immunized so far.