The World Health Organization (WHO) has released a report on 31 December detailing the risk assessment and guidance, on a series of recently observed SARS-CoV-2 variants.
The global health institution highlighted a quartet of variants that are currently in circulation in its press release.
D614G Substitution Variant – the Primary Virus
The SARS-CoV-2 variant with a D614G substitution in the gene encoding the spike protein is currently the most dominant form of the global virus.
It was initially observed in late January or February 2020 before overwhelming the strain identified in China.
In June, it became the most dominant strain, having increased infectivity and transmission to previous strains. However, it does not cause greater illness nor worsen effectiveness of existing laboratory diagnostics, therapies, vaccines, or epidemiologic efforts.
The Danish "Cluster 5" Variant
This SARS-CoV-2 variant was identified in North Jutland, Denmark, in August and September.
It was characterized by its link to infection among farmed mink before subsequently transmitting to humans. It possesses multiple mutations that weren't observed previously.
Experts have raised concern that it could result in reduced virus neutralization that would decrease the extent and duration of immune protection from infection recovery or vaccination.
The "Cluster 5" variant is currently being assessed for virus neutralization among humans infected with it, though Denmark has reported only 12 human cases in September, without indication of widespread transmission.
The Variant in the UK
Three weeks ago, the UK initially reported to WHO SARS-CoV-2 variant B117, which has since been observed to have 23 nucleotide substitutions without phylogenetic relation to the virus circulating at the time in the country.
The variant initially appeared in Southeast England but has since replaced virus lineages in the area as well as in London.
A preliminary assessment indicates the variant has increased transmissibility, but no change in disease severity—as per hospitalization length and 28-day case fatality—nor reinfection risk.
Another of this variant's mutations appears to have affected diagnostic PCR assays with an S gene target, however, the impact is not anticipated to be significant.
As of this week, the variant has been reported in 31 other countries, territories, areas in 5 of the 6 WHO regions.
The South Africa 5O1Y.V2 Variant
A new variant was detected by South African authorities on December 18, spreading rapidly among 3 provinces with an N501Y mutation.
A month earlier, routine sequencing observed this variant had largely replaced other SARS-CoV-2 viruses in regions of Eastern Cape, Western Cape, and KwaZulu-Natal provinces. Despite this rapid displacement and an observed higher viral load that could indicate transmissibility, further research is needed.
Additionally, WHO indicated there is currently no evidence of this variant being associated with more severe disease or worse outcomes, though again, more research is needed. As of this week, is has been reported in 4 other countries.
Response to Variants
Aside from affected nation's authorities currently undergoing epidemiological and virologic assessments on these variants, as well as the addition of the UK and South Africa variants' genomic data to the Global Initiative on Sharing Avian Influenza Data (GISAID), WHO highlighted a series of actions initiated to respond to the new threats.
Intensified sampling in affected regions would have to be carried out to interpret new variant circulation and spread.
National scientific teams would have to observe the mutations' effects on reinfection, vaccination, diagnostic testing, infection severity, and transmissibility.
WHO and research/government authorities would have to collaborate to analyze epidemiologic, modelling, phylogenetic and laboratory findings as they become available.
WHO and national authorities would have to work together to identify means of strengthening SARS-CoV-2 surveillance systems, as well as implementing or bolstering genetic sequencing capacity to evaluate variants.
Community engagement needs to be improved and communication to describe the public health implications of SARS-CoV-2 variants to the public, with emphasis on continued social distancing strategies while research continues.
Variant Risk Assessment
WHO stressed the commonality of viruses to change over time, often without direct benefit to its infectiousness or transmissibility, and sometimes limiting propagation. They also noted that virus mutation risk increases with the frequency of human and animal infections.
Though initial assessment implicates the UK and South African variants do not cause a change in clinical presentation or severity, their potential for higher case incidence could lead to increased COVID-19 related hospitalizations, and therefore, deaths. As such, WHO warned more intensive public health response may be necessary to control variant transmission, pending research.
Existing strategies of disease control—including epidemiological surveillance, strategic testing, contact tracing, and adjusted public health and social measures—are advised to continue during the investigation of the variants.
WHO also advised countries increase routine systematic sequencing of SARS-CoV-2 viruses, when possible, to better monitor variant emergence.
The authority advised national and regional health organizations to work with travel, transport, and tourism sectors to assure travellers to and from countries affected by new variants are informed on variants and resourced to prevent spread.