Prevalence of Covid-19's Delta variant among specimens sequenced over past 4 weeks exceeded 75 per cent: WHO

Over the past week, the highest numbers of new cases were reported from Indonesia, the UK, Brazil, India and the US

The prevalence of the highly-transmissible Delta variant of Covid-19 among specimens sequenced over the past four weeks exceeded 75 per cent in many countries worldwide, including India, China, Russia, Israel and the UK, the WHO has said.

In the Covid-19 Weekly Epidemiological Update published July 20, the World Health Organisation said that despite efforts to extend vaccination coverage, many countries across all six WHO regions continue to experience surges in coronavirus cases.

Over the past week, the highest numbers of new cases were reported from Indonesia (350,273 new cases; a 44 per cent increase), the UK (296,447 new cases; 41 per cent increase), Brazil (287,610 new cases; 14 per cent decrease), India (268,843 new cases; 8 per cent decrease) and the US (216,433 new cases; 68 per cent increase).

The update noted that as of July 20, a total of over 2.4 million SARS-CoV-2 sequences have been submitted to GISAID, the global science initiative and primary source that provides open access to genomic data.

Over 220,000 (9 per cent) of SARS-CoV-2 sequences submitted to GISAID are confirmed as the Delta variant.

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"According to GISAID data, as of 20 July, the prevalence of Delta among the specimens sequenced over the past 4 weeks exceeded 75 per cent in many countries worldwide including Australia, Bangladesh, Botswana, China, Denmark, India, Indonesia, Israel, Portugal, Russian Federation, Singapore South Africa and the United Kingdom," the update said.

It reiterated that the Delta variant is expected to "rapidly outcompete" other variants and become the dominant circulating lineage over the coming months.

Globally, cases of the Alpha variant have been reported in 180 countries, territories or areas, while 130 countries reported cases of the Beta variant; 78 countries cases of the Gamma variant and 124 countries have reported cases of the Delta variant.

Further, the update said that growing evidence supports the increased transmissibility of the Delta variant as compared to non-Variants of Concern (VOCs) but the exact mechanism for the increase in transmissibility remains unclear.

The update cited a recent study from China during an outbreak of the Delta variant that examined the time interval from the exposure of a quarantined population to the first positive Polymerase Chain Reaction (PCR) result and found that the interval may be shorter for the Delta variant when compared to non-VOCs.

"Moreover, the viral load of the first positive test of Delta infection was over 1,200 times higher than non-VOCs, suggesting that this VOC may be able to replicate faster and be more infectious during the early stages of infection."

Another study from Canada analysing data from over 200,000 Covid-19 cases showed an increase in virulence of the Delta variant when compared to non-VOCs.

Among the Covid-19 cases, the risk of hospitalisation, ICU admission and death associated with the Delta variant compared to non-VOCs increased by 120 per cent, 287 per cent and 137 per cent respectively.

The update said that the global number of new cases reported for the July 12-18 week was over 3.4 million, a 12 per cent increase as compared to the previous week.

Globally, Covid-19 weekly case incidence increased with an average of around 490,000 cases reported each day over the past week as compared to 400,000 cases reported daily in the previous week.

The South-East Asia region reported over 829,000 new cases and over 16,000 new deaths, increases of 16 per cent and 12 per cent, respectively as compared to the previous week.

"Weekly case incidence and mortality in India and Sri Lanka continue to decline, with the regional trends being driven mainly by marked increases in Indonesia, Thailand and Myanmar," the update said.

In the region, the highest numbers of new cases were reported from Indonesia (350,273 cases; 128.1 cases/100,000; +44 per cent), India (268,843 cases; 19.5 cases/100,000; -8 per cent) and Bangladesh (82,800 cases; 50.3 cases/100,000; +9 per cent).

The highest numbers of new deaths were reported from Indonesia (7,118 deaths; 2.6 deaths/ 100,000; +21 per cent), India (5,569 deaths; 0.4 deaths/100,000; -8 per cent) and Bangladesh (1,475 deaths; 0.9 deaths/100 000; +9 per cent). 

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