University of Cambridge The mpox virus appears to be circulating silently in parts of Nigeria, in many cases without the symptoms typically associated with the disease, according to new research led by scientists from the University of Cambridge and partners in Nigeria. The findings may have implications for controlling the spread of the disease. In a study published today in Nature Communications, researchers show that exposure to the mpox virus can occur without recognised illness, and that residual immunity from historic smallpox vaccination continues to shape how the virus spreads in human populations.
Mpox is a zoonotic virus – that is, one that initially jumped species to spread from animals to humans. It is closely related to smallpox. For decades, smallpox vaccination provided broad protection against related viruses such as mpox. Following the eradication of smallpox, routine vaccination stopped in 1980 and a growing proportion of the population lost this protection. This shift has been accompanied by renewed mpox transmission, culminating in outbreaks seen in multiple countries between 2022 and 2024.
While most public health attention has focused on symptomatic mpox cases, little is known about how often people may be exposed to the virus without developing classical disease.