Explained: Why the mutated coronavirus variants are so worrisome

Insufficient surveillance in most countries has obscured recognition of variants circulating in many places

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 year-end 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.
 
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.