While the COVID pandemic is far from over, it is receding again as the Northern Hemisphere enters the summer months. The latest summary from the WHO's weekly (June 15th) Epidemiological Report reads:
In the past week, the number of new COVID-19 cases and deaths continued to decrease, with over 2.6 million new cases and 72 000 new deaths reported globally. While the number of cases reported globally now exceeds 175 million, over the past week, the lowest weekly case incidence since February 2021 was reported. Declines in the number of new weekly cases, compared to the previous week, were reported across all Regions except for the African Region. The number of new deaths reported in the past week decreased across all the regions except for the African and South-East Asia Regions.
In this edition, a special focus update on variants is provided, including a newly designated variant of interest (VOI), along with the geographical distribution of variants of concern (VOCs) Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1) and Delta (B.1.617.2). This edition also includes an update about strengthening public health intelligence through event-based surveillance, specifically learning from the COVID-19 pandemic.
All regions of the world - with the exception of Africa - are reporting declines in cases. The trend in Africa (up 44% over last week), is concerning however.
The World Health Organization also announced the addition of a new Variant of Interest, dubbed Lambda (C.37), which was first reported in Peru last fall. They describe it as:
On 14 June 2021, a variant assigned to Pango lineage C.37, GISAID clade GR/452Q.V1, NextStrain clade 20D, was designated as a global VOI, and assigned the WHO label “Lambda”. This variant has been monitored as an alert for an extended period, and upon more information and updated assessments, is now considered as meeting the VOI working definition based upon evidence of continued emergence and suspected phenotypic implications.
Lambda has been associated with substantive rates of community transmission in multiple countries, with rising prevalence over time concurrent with increased COVID-19 incidence. The earliest sequenced samples were reported from Peru in August 2020.
As of 15 June 2021, over 1730 sequences have been uploaded to GISAID from 29 countries/territories/areas in five WHO regions.
Elevated prevalence has been noted particularly in South America in countries such as Chile (31% overall prevalence among submitted sequences 6since first detected in this location to date), Peru (9%), Ecuador (8%), and Argentina (3%).
Authorities in Peru reported that 81% of COVID-19 cases sequenced since April 2021 were associated with Lambda.
Argentina reported increasing prevalence of Lambda since the third week of February 2021, and between 2 April and 19 May 2021, the variant accounted for 37% of the COVID-19 cases sequenced.
In Chile, prevalence of Lambda has increased over time, accounting for 32% of sequenced cases reported in the last 60 days – co-circulating at similar rates to variant Gamma (33%), but outcompeting variant Alpha (4%) over the same period.
Lambda carries a number of mutations with suspected phenotypic implications, such as a potential increased transmissibility or possible increased resistance to neutralizing antibodies.
It is characterised by mutations in the spike protein, including G75V, T76I, del247/253, L452Q, F490S, D614G and T859N; however, there is currently limited evidence on the full extent of the impact associated with these genomic changes, and further robust studies into the phenotypic impacts are needed to better understand the impact on countermeasures and to control the spread.
Further studies are also required to validate the continued effectiveness of vaccines.
The World Health Organization currently lists 4 VOCs (Variants of Concern) and 7 VOIs (Variants of Interest), and continues to monitor dozens more. Whether Lambda has what it takes to challenge the more worrisome VOCs remains to be seen.
For now, the Delta Variant appears to be of most concern (see UK PHE Technical Briefing, Revised Risk Assessment, & Household Transmission Study On COVID Variant B.1.617.2 (Delta)).