Any differences in immune responses in health care workers versus the general population were minimal, which the researchers said indicates that exposure isn’t limited to medical settings.
“What we’re seeing is evidence that mpox exposure doesn’t always look like the textbook description,” lead author Adam Abdullahi, PhD, of the University of Cambridge and the Institute of Human Virology Nigeria, said in a university news release. “In some people, particularly in settings with partial population immunity, the virus may circulate quietly, leaving immune footprints that routine clinical surveillance will miss.”
The strongest antibody increases were directed against antigens that are important targets of immune responses, suggesting that certain immune markers could be used for detecting recent exposures in population studies.
To put the results into an epidemiologic context, the team also analyzed more than 100 mpox virus genomes collected in Nigeria over several years. Genomic reconstruction showed slow epidemic growth, frequent transmission dead-ends, and limited clustering, which the authors said is consistent with ongoing spread limited by partial immunity in the population.
“Mpox is not spreading unchecked in Nigeria and across the region, but neither is it absent,” senior author Ravindra Gupta, BMBCh, PhD, MPH, of the University of Cambridge, said. “Instead, it appears to circulate at low levels, shaped by the lingering effects of smallpox vaccination in older generations.”
The researchers said that the findings have important implications for disease surveillance. “Instead of relying solely on reported cases or symptoms, monitoring populations by testing blood samples for antibodies to reveal exposure to the virus will be important for understanding how it is spreading and guiding targeted vaccination in our settings,” coauthor Alash’le Abimiku, PhD, of the Institute of Human Virology Nigeria, said.
Lingering symptoms include skin scars, functional impairment
The second study, published today in the Annals of Internal Medicine, involved 154 people in New York City and Houston diagnosed as having clade 2 mpox from May 2022 to January 2023 and 201 never-infected but at-risk participants. Follow-up was 11 to 18 months.
Participants completed psychosocial and behavioral self-assessments, and a clinician evaluated post-mpox participants using a clinical history and physical examination, to determine any link between lingering mpox physical symptoms and medical history, mpox severity, and sociodemographic factors.
The median participant age was 35 years, and most were Black or Hispanic (80%), male (90%), men who have sex with men (67%), and publicly insured (56%).
Our findings provide informative context for characterizing the types of, and risk for, persistent physical and psychosocial sequelae that may occur because of mpox.
“Little was known about persistent sequelae of mpox before the 2022 multinational clade II mpox virus outbreak,” wrote the Life After Mpox (LAMP) Study team.
The percentage of participants reporting increased psychobehavioral symptoms was comparable between the two groups. In total, 58% of post-mpox participants had one or more persistent effects, and 56% were related to physical appearance (mainly skin scarring), of which 51% occurred at one or two sites.
Thirteen percent of post-mpox participants had functional impairment, of whom 50% and 35% had ongoing anorectal and urinary dysfunction, respectively. Two percent reported limitations to their activities of daily living.
“Mpox remains a public health threat, with the World Health Organization declaring a public health emergency in response to a 2024 upsurge of clade I and clade II mpox virus cases in the Democratic Republic of the Congo and surrounding countries,” the investigators wrote. “That outbreak has prompted calls for research into the long-term sequelae of clade I mpox.”
“Although our participants were affected by clade II mpox, which has different acute symptom severity and mortality than clade I, our findings provide informative context for characterizing the types of, and risk for, persistent physical and psychosocial sequelae that may occur because of mpox,” they concluded.
