Mpox often causes serious illness, even death, in people with advanced HIV

In people with advanced HIV disease, the MPOX virus — formerly known as monkeypox — often causes serious illness with a fatality rate of about 15 percent, researchers reported Tuesday.

The severity of the infection warrants including mpox among the opportunistic diseases that are particularly dangerous for people with advanced HIV, the researchers said at the Seattle Retroviruses and Opportunistic Infections Conference.

“These results make it very, very clear that every single person with MPOX should get tested for HIV,” said Dr. Chloe Orkin, HIV expert at Queen Mary University of London and the researcher who led the work. She and her colleagues also detailed the findings in the journal The Lancet on Tuesday.

The mpox outbreak started spreading 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 estimate that 40 to 50 percent of those infected are living with HIV

If antiretroviral drugs keep HIV at bay, mpox is about as dangerous as it is for people without HIV infection. But a CDC study last year, along with observations from previous outbreaks in Nigeria, showed that mpox was more severe and far more deadly in people with high HIV levels

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 in these patients and the number of CD4 cells, a type of cell in the immune system.

The typical range for CD4 cells is between 500 and 1,500 per cubic millimeter of blood. All 27 deaths in the study were in people with fewer than 200 CD4 cells. Mpox killed nearly 30 percent of those with fewer than 100 CD4 cells.

The nature of the disease was also strikingly different in patients with a weakened immune system. While most people infected with mpox have lesions only at the site of exposure, those with advanced HIV developed large, ulcerated lesions that were 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 horrifying,” said Dr. Orkin. “That’s because the immune system can’t contain the virus at all.”

Many patients also had nodules in their lungs that caused acute shortness of breath, she added.

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

Patients would need antibiotics to prevent other opportunistic infections and should be offered two doses of the vaccine injected under the skin instead of between layers of skin as is currently the case, Dr. Orkin.

The United States added mpox to its list of possible opportunistic infections in people living with HIV in September. The World Health Organization plans to discuss doing the same over the next few months, said Dr. Meg Doherty, Director of Global Programs for HIV, Hepatitis and Sexually Transmitted Infections at WHO

The new data are a “compelling argument” for including mpox in the list of opportunistic diseases, said Dr. Doherty.

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