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BRISBANE, Australia -- The elevated risk of severe mpox in people living with HIV appeared restricted to those with uncontrolled HIV or immunosuppression from other conditions, according to an update on the global outbreak from World Health Organization (WHO) researchers.

Of more than 32,000 cases of mpox (formerly monkeypox) reported worldwide where patients' HIV status was known, 52% were HIV-positive, reported Ana Hoxha, MSc, an epidemiologist at the WHO in Geneva, during an oral presentation at the biannual International AIDS Society Conference on HIV Science.

Rates of immunosuppression, concurrent sexual transmitted infections (STIs), hospitalization, and death were all higher among the mpox patients with HIV:

• Immunosuppression: 24.6% vs 0.6% in those without HIV
• Concurrent STIs: 5.5% vs 3.8%
• Hospitalization: 4.3% vs 3.0%
• Death: 0.30% vs 0.03%

Statistical analysis demonstrated that immunocompromised patients with HIV were twice as likely to be hospitalized for mpox infection, while no additional risk was seen for HIV-positive people without immunocompromise, Hoxha detailed.

"The high prevalence of HIV among mpox cases highlights the importance of HIV testing for individuals that do not know their status," Hoxha said. "Post diagnosis represents a good occasion for patients to be screened for HIV so that they are aware of their status."

Data for the study were derived from 82,290 confirmed mpox cases reported by WHO Member States from January 2022 to January 2023, of which 38.9% had a documented HIV status.

Among the full study population, people who were HIV-negative but immunocompromised were more than three times as likely to require hospitalization, according to the findings. Women, children under the age of 4, and adults over 65 were up to twice as likely to require hospitalization following an infection, although mpox was more rare in these populations. (More than 90% of the cases recorded have occurred among those who identify as gay, bisexual, or other men who have sex with men [GBMSM].)

In commenting on the study, Charles Gilks, MBBS, PhD, dean of the School of Public Health at the University of Queensland in Brisbane, said: "The study team concluded that since uncontrolled HIV and the immunosuppression that comes from that may lead to disproportionate mpox morbidity, health systems need to ensure that people living with HIV know their status and are linked to care and start on antiretroviral therapy. They also know that for people with unknown HIV status, mpox testing can be an important opportunity for HIV testing, prevention, and care."

Their new findings build on prior evidence suggesting a link between uncontrolled HIV and severe mpox cases, research that has often been conducted on a national scale in higher-income nations, Gilks highlighted.

"Since it was WHO's surveillance system, it therefore provides a more global picture that includes low-income countries," he said at a press briefing. "There's been a paucity of data on mpox infection with or without HIV infection from low- and middle-income countries."

Of the 32,004 cases where HIV status was know, 16,633 were HIV-positive and 15,371 were HIV-negative, and immunosuppression status was known for about a third. The vast majority involved men. About two-thirds of these cases involved GBMSM, 12% were non-GBMSM, and status was unknown in about a fifth of the cases. Hospitalizations occurred in 1,172 individuals, and 62 deaths were recorded, though Hoxha said this is likely an undercount as countries classify mpox mortality using different definitions.

"This is the largest outbreak of mpox recorded so far," Hoxha said. "From this case-based data we know that the main demographics of cases in this outbreak have been that they are adult males between the ages of 18 and 60 years old." Among the HIV-positive subset, more than 7,000 cases were recorded in people ages 30-39.

Sexual encounters were, by far, the most common cause of mpox transmission, accounting for more than 75% of transmissions. Person-to-person household contacts accounted for another 5-10% of the transmissions, she noted.

One of the limitations of the analysis was that HIV status was not available for more than 60% of the total cases. "Currently, there is no clinical guidance recommending HIV screening for mpox cases," she said. "It is not clear if cases with no information are more likely to be affected by HIV or not."

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