Why strengthening genomic surveillance is an imperative

A recent study revealed that the rate of genetic changes in the monkeypox virus was higher than expected

Ever since it was first reported in humans in 1970, monkeypox virus infections have been largely restricted to countries in Central and Eastern Africa until recently. Early in 2022, multiple cases were identified in Spain and several cases were reported from countries where the disease is not endemic, including regions in Europe and North America, and in patients with no history of travel to endemic regions.

Following a rapid rise in cases, the World Health Organization (WHO) on July 23, 2022 declared the 2022 monkeypox outbreak as a Public Health Emergency of International Concern (PHEIC). As of early August 2022, over 25,000 cases of monkeypox have been reported from 83 countries, 76 of which have never historically reported monkeypox.

The accelerated use of genomics as a tool to understand outbreaks in the last half decade has left an indelible mark during the ongoing COVID-19 pandemic and has seen a wider deployment of sequencing infrastructure across the world. Genomic surveillance of pathogens could provide unique insights to understand the outbreak better, track the spread of pathogens and provide immense opportunities for public health decision-making as well as for epidemiology.

Researchers from across the world have made available over 650 complete genome sequences of monkeypox isolates to date in public domain databases including GISAID and GenBank. This includes over 600 genomes which were sequenced this year alone from over 35 countries, including genomes of two isolates from India, collected from Kerala. 

ALSO READ: The monkeypox virus: origin, symptoms and vaccine 

The monkeypox virus has a DNA genome of around 2,00,000 base pairs, roughly six times larger than that of SARS-CoV-2. Like other viruses, the monkeypox virus evolves by the accumulation of genetic errors, or mutations, in its genome when it replicates inside a host. Information about mutations occurring in different genome sequences of the monkeypox virus across different regions can, thus, provide essential insights into how the virus is evolving, its genetic diversity and other factors that may be relevant to the development of diagnostic tools.

Being a DNA virus, the monkeypox virus like other poxviruses was believed to have a small rate of accumulating genetic changes compared to viruses with an RNA genome like SARS-CoV-2, which have a much larger rate of mutations. For poxviruses, this rate is estimated to be as low as a couple of genetic changes every year. A recent study, however, revealed that the observed rate of genetic changes in the virus was higher than expected — average of around 50 genetic changes. The higher-than-expected rate of evolution coupled with the rapid rise in monkeypox cases across the world could potentially be due to highly parallel evolution in a large number of individuals simultaneously, as the present outbreak came out of a superspreader event.