Geneva: Results from a recent preprint study in the United States of America suggest that the Delta variant has greater replication fitness as compared to the Alpha variant, meaning that Delta has the propensity to replicate more easily and is in turn more infectious.
The study identified a key spike protein mutation (P681R at the furin cleavage site) as the molecular determinant for the enhanced fitness of the Delta variant and its dominance over the Alpha variant.
The authors of the study screened nearly 30,000 records, of which only 5 were identified as providing evidence that the true value of the R0 of the Delta variant is likely under-estimated as the R0 estimates in the studies identified were taken at the time when variable movement restrictions were in place in most parts of the world.
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A preliminary population-level observational study conducted in Israel found that infection with the Alpha variant did not lead to higher case fatality rates. This finding contradicts previous studies from the United Kingdom that indicated an increase in the risk of severe outcomes and mortality associated with the Alpha variant. These findings could nonetheless be influenced by several factors such as much younger general population, high vaccination coverage and extensive free testing throughout Israel.
Another prospective longitudinal household study (preprint) found a higher secondary attack rate among cases infected with the Alpha variant (77.8%) as compared to those infected with non-Variant Of Concerns (42.5%) in Norway, suggesting the potential for very high household transmission levels for the Alpha variant. The same study also found that primary cases experiencing loss of taste/smell were associated with a significant increase in the onwards secondary attack rates, which could also be due to the observed increase in viral load in these cases.
Globally, cases of the Alpha variant have been reported in 192 countries (three new countries since last week), while 141 countries (four new countries) have reported cases of the Beta variant; 86 countries (no new country) have reported cases of the Gamma variant; and 163 countries (seven new countries) have reported cases of the Delta variant.
“The emergence of these Variants of Concern highlight the importance of maintaining public health and social measures (PHSM) and the need to increase vaccination coverage against SARS-CoV-2,” the World Health Organization stated in its weekly epidemiological report published on August 24, 2021.
– global bihari bureau
