Mpox often leads to severe illness or even death in people with advanced HIV

In people with advanced HIV disease, the mpox virus – formerly known as monkeypox – often causes severe disease, with a mortality rate of around 15%, researchers reported Tuesday.

The severity of the infection warrants the inclusion of mpox among the opportunistic conditions especially dangerous for people with advanced HIV, researchers said at the Conference on Retroviruses and Opportunistic Infections in Seattle.

“These findings make it very, very clear that everyone with mpox should be tested for HIV,” said Dr Chloe Orkin, an HIV expert at Queen Mary University of London and researcher who led the work. She and her colleagues also described the findings in The Lancet on Tuesday.

The mpox outbreak began to unfold last May. Although the number of cases has slowed to a trickle in most regions, it has so far affected around 86,000 people in 110 countries and killed 92. Several studies have estimated that 40-50% of those infected were living with HIV.

When antiretroviral drugs control HIV, mpox is about as dangerous as it is for those who are not infected with HIV. But a CDC study last year, along with observations of previous outbreaks in Nigeria, indicated that mpox was more severe and far more deadly in people with high levels of HIV.

In the new study, an international group of clinicians followed 382 adults in 28 countries who had advanced HIV disease and were infected with mpox. They analyzed the amount of HIV and the number of CD4 cells, a type of immune system cell, in these patients.

The typical range for CD4 cells is 500 to 1,500 per cubic millimeter of blood. The 27 deaths in the study involved people who had fewer than 200 CD4 cells. Mpox killed almost 30% of people with less than 100 CD4 cells.

The nature of the disease was also very different in patients with weakened immune systems. While most people infected with mpox show lesions only at the site of exposure, those with advanced HIV developed large ulcerated lesions teeming with virus throughout the body.

“It’s on your back, it’s on your feet, it’s in your eyes, it’s everywhere – it’s horrible,” Dr Orkin said. “It’s because the immune system is not able to contain the virus at all.”

Many patients also had nodules in their lungs that caused acute respiratory distress, she added.

Adding mpox to the list of opportunistic infections in people with advanced HIV would encourage health workers to identify and prioritize patients most at risk of serious illness and death.

Patients would need antibiotics to prevent further opportunistic infections and should be offered two doses of the vaccine injected under the skin, rather than between the layers of the skin as is currently done, Dr Orkin said.

The United States added mpox to the list of possible opportunistic infections in people living with HIV in September. The World Health Organization plans to discuss doing the same in the coming months, said Dr Meg Doherty, director of global programs on HIV, hepatitis and sexually transmitted infections at WHO.

The new data make a “compelling argument” for adding mpox to the list of opportunistic conditions, Dr. Doherty said.

In areas of the world where people living with HIV may not have access to mpox vaccines or treatment for mpox and HIV, she said, “it should just raise awareness that we have more to do in these areas than we have”.