In a groundbreaking revelation, researchers have unveiled that the virus, once referred to as monkeypox, which triggered an extraordinary global outbreak in 2022, had been silently circulating among humans for over five years before unleashing a worldwide public health crisis.
The discovery of this concealed and persistent transmission of the MPXV virus, which was renamed “mpox” last year, has intensified the call for enhanced global surveillance to eradicate this disease from human populations and prevent its resurgence.
Dr. Áine O’Toole, an evolutionary biologist at the University of Edinburgh who delved into the virus’s evolution, emphasized the need for vigilance even when outbreak case numbers are low, underscoring the importance of early detection and swift containment to thwart the establishment of such viruses in the human population.
Mpox: A Historical Perspective
Mpox, formerly recognized as monkeypox, was initially identified in the 1950s during outbreaks that afflicted monkeys in research laboratories. The first documented human case emerged in 1970 in the Democratic Republic of the Congo (DRC), and sporadic cases were primarily localized within the DRC and Nigeria over the subsequent 50 years.
Until 2020, human infections of mpox were predominantly attributed to contact with rodents that carried the virus, typically in regions where the disease was endemic. Instances of human-to-human transmission were rare, with affected individuals typically confined to the same households.
However, the global mpox outbreak in 2022 defied this historical pattern. The study published in the journal Science by O’Toole and her team delineates how viruses collected from patients in 2022 exhibited a substantially higher number of mutations than anticipated. While the mpox virus was projected to acquire one mutation every three years, the samples from 2022 presented a staggering 42 mutations when compared to virus specimens obtained from Nigeria in 2018.
Upon closer examination, it was revealed that the majority of these mutations were driven by interactions with the human immune system, notably a specific antiviral enzyme known as apobec3. This finding indicates that the human immune system played a pivotal role in fueling the virus’s evolution, signaling its sustained circulation among humans. Based on the mutation rate, scientists estimate that mpox had been present in human populations since at least 2016.
Global Implications and Continued Spread
The global outbreak of mpox was primarily linked to a lineage referred to as B.1. Efforts, including public health advice and vaccination programs, mainly aimed at men who have sex with men, have resulted in a decline in cases associated with this lineage. However, countries such as the UK, the US, Portugal, India, and Thailand continue to report cases linked to other virus lineages, all tracing back to Nigeria. This suggests that the human epidemic which ignited the 2022 outbreak continues to persist unabated.
Dr. Emma Hodcroft, principal investigator at the Swiss Tropical and Public Health Institute in Switzerland, who was not involved in the study, pointed out that the sustained circulation of the virus among humans long before 2022 set the stage for a global outbreak. She emphasized the need for equitable training, funding, and equipment distribution to ensure global readiness for emerging viral threats.
The revelation that mpox had remained in sustained circulation among humans prior to 2022 underscores the critical importance of proactive prevention and eradication strategies and serves as a stark reminder that subtle shifts in viral behavior can pose significant threats. Global vigilance is essential to address and mitigate such challenges.
