WHY THE MUTATED CORONAVIRUS STRAINS ARE SO WORRISOME
Viruses mutate all the time, including the coronavirus that’s caused the Covid-19 pandemic. Although most changes are innocuous, several mutants have sparked alarm.
What are the most worrisome variants?
The World Health Organisation (WHO) uses the term “variants of concern” to signify strains that pose additional risks to public health, and “emerging variants of interest” for those that warrant close monitoring because of their potential risk. These have been assigned names or codes by the various research groups and public health agencies investigating them. As of May 11, the WHO has identified four variants of concern and six variants of interest.
▶ The variant that emerged in England in September 2020, B.1.1.7, contributed to a surge in cases that sent the UK back into lockdown in January. Other countries in Europe followed, before it became a dominant strain in the US.
▶ In southern Africa, hospitals faced pressure from a resurgence driven by another variant, 501Y.V2, that first appeared there in August 2020.
▶ The P.1 variant, first spotted in the Amazon city of Manaus in December, has contributed to a surge in cases that’s strained Brazil’s health system and led to oxygen shortages.
▶ The B.1.617 lineage raising alarm in India is the latest to be designated a variant of concern by the WHO, based on early evidence suggesting it has higher rates of transmission, and some propensity to evade antibodies, including bamlanivimab, a monoclonal antibody therapy developed by Abcellera Biologics and Eli Lilly & Co. The lineage, identified in October and detected in 44 countries, has spawned three versions — B.1.617.1, B.1.617.2 and B.1.617.3 — amid a dramatic spike in cases. Also, any impacts on effectiveness of vaccines or therapeutics, or reinfection risks, remain uncertain, the WHO said.
How quickly have the strains spread?
Rapidly, aided initially by yearend holidays traditionally associated with family and social gatherings. As of April 27, imported cases or community transmission of the B.1.1.7 variant had been reported in 139 countries, while the 501Y.V2 variant was found in 87 countries and the P.1 variant in 54, according to the WHO. Insufficient surveillance in most countries, including the US, has obscured recognition of variants circulating in many places.
What are the concerns with these variants?
The concerns relate to their transmissibility, or propensity to spread; the severity of illness they cause; neutralisation capacity, or the likelihood they will infect people who have recovered from a previous bout of Covid-19; potential impact on vaccination through their ability to evade the protection that immunisations are designed to generate.
Insufficient surveillance in most countries has obscured recognition of variants circulating in many places
Are some mutations more important?
Yes. Scientists pay most attention to mutations in the gene that encodes the SARS-COV-2 spike protein, which plays a key role in viral entry into cells. Targeted by vaccines, this protein influences immunity and vaccine efficacy. The B.1.1.7, 501Y.V2, P.1 and B.1.617 variants all carry multiple mutations affecting the spike protein. That raises questions about whether people who have developed antibodies to the “regular” strain will be able to fight off the new variants.