Mpox Can Infect and Replicate in the Brain, NIH Study Finds

Researchers at the U.S. National Institutes of Health (NIH) have discovered that the mpox virus can persist and replicate within the human brain. The finding, released as a preprint on April 9, 2026, comes from a detailed autopsy of a patient who died from the infection.

The case involved a 38-year-old man with advanced human immunodeficiency virus (HIV) who was infected with the clade IIb strain of mpox. Despite receiving repeated antiviral therapy over a period of more than seven months, the patient’s condition worsened, eventually leading to his death.

The NIH findings suggest that mpox is capable of spreading significantly further than the skin lesions that typically characterize the disease. During the autopsy, scientists found the virus infecting the brain and continuing to multiply there, although viral levels in the brain were lower than those found in other tissues.

Drug Resistance and Viral Evolution

The autopsy also revealed that the virus had developed resistance-associated mutations. Specifically, the case showed mutations linked to resistance to tecovirimat, an antiviral drug used to treat mpox.

This discovery aligns with other studies indicating that tecovirimat may offer little benefit for many patients. The ability of the virus to persist and evolve within the brain demonstrates a potential pathway for the development of drug-resistant strains in immunocompromised individuals.

Public Health Implications

Health researchers have warned that these findings highlight significant risks in regions where mpox is spreading among populations with high rates of untreated HIV, particularly in parts of Africa.

The situation is compounded by a reduction in global health funding. Researchers warned in September 2025 that cuts to funding are undermining HIV care and the response to outbreaks. These conditions may create an environment where infections last longer and lead to more severe disease manifestations.

The current landscape of the mpox outbreak is complex, with multiple strains circulating simultaneously:

• The clade IIb strain has been the primary driver of a global outbreak since 2022.
• Separate outbreaks linked to distinct clade I variants have continued in various parts of Africa.
• The World Health Organization reports that cases are increasingly concentrated on the African continent.

The ability of the virus to replicate in the brain of a patient with advanced HIV underscores the danger posed to individuals with severely weakened immune systems and the necessity of sustained global health interventions to manage both HIV and mpox.