Genome sequencing of thousands of SARS-CoV-2 samples shows that the increase in incidence is due to the emergence of new coronavirus variants.
Even though SARS-CoV-2 has only 15 genes, it constantly mutates. Most of these changes are minor, but some affect the transmission speed.
The authors of the new work initially analyzed the genomes of 150 strains of SARS-CoV-2. They classified outbreaks into stages: index (no outbreak), rise, exponential rise, and fall. The ease of transmission of a virus is determined by the R-value, or reproductive number, where R is the average number of new infections caused by each infected person.
They combined all this information into a metric called GENI to identify the pathogen’s genome. A comparison of the GENI scores with the epidemic phase showed that the increase in genetic variability occurred just before the incidence.
When the British government introduced a lockdown in late March, the number of new cases stabilized, but mutations continued to rise. This shows that measures such as banning gatherings and social distancing effectively control the spread of the disease amid the rapid evolution of the virus.