The assertions about a more aggressive strain spreading across human populations is merely conjecture at this point. It is necessary to conduct rigorous studies that couple clinical data (such as patient features and outcomes) with changes in the virus, as well as laboratory studies that test the effect of mutations on the ability of the virus to replicate and spread. Without this evidence, it is speculative to assign spread and disease severity to mutations. This brief examines the claims that changes in the genome of the SARS-CoV-2 virus are making it spread faster or increasing its virulence.
The Implication of a Mutating Virus
Mutations can affect the efficacy of sequence-based diagnostic methods and impose restrictions on vaccine design. The most commonly used diagnostic tool targets specific regions of the genome, and if a mutation occurs in this region, the test may lead to a false negative result. Furthermore, sequence-based vaccines may have to incorporate the D164G mutation and account for its effects. Sequencing efforts all over the world are flagging regions that are mutating to guide diagnostics and vaccine design.
Mutations are a part of the natural life cycle of any virus, particularly RNA viruses. The many mutations observed in the SARS-CoV-2 sequences are therefore expected. However, it is unclear whether these mutations are meaningful, i.e. if they change the biological properties of the virus. Studies to evaluate this are yet to be conducted. While it is plausible that some mutations may allow the virus to spread more effectively, it is premature to conclude that such mutations are driving the current global spread of the virus.
Analyses of genome sequences from across the globe have revealed the presence of different SARS-CoV-2 clades. However, there is no experimental evidence to suggest a difference in aggressiveness amongst these. Moreover, the effects of the observed mutations in SARS-CoV-2 on the properties of the virus are yet to be evaluated in clinical or experimental studies. Since multiple factors influence viral spread, the mere prevalence of a virus clade cannot be used as a proxy for biological traits such as increased transmission and disease severity. Some countries are affected more than others due to a complex mix of the biology of the virus and the behaviour of the infected and susceptible population. An exhaustive list of the major factors can only emerge over time, as more data becomes available.
Reference & source information: https://www.orfonline.org/
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