Dr. Shyam P Lohani

Since its origination from Wuhan in 2019, the SARS COV-2 virus has undergone thousands of mutations. All the mutations are not significant in their pathogenicity and transmissibility. There are several variants which are termed as “Variants of Concern”. Owing to its significantly higher rate of transmissibility, the Delta variant of the coronavirus is becoming the globally dominant strain.
The Delta (B.1.617.2) coronavirus variant originally discovered in India last December has now become one the most worrisome strains of the coronavirus circulating globally. Research suggests it may be the most transmissible variant yet, i.e., 40 to 60 per cent more contagious than the Alpha (U.K./B.1.1.7) variant which itself fueled numerous waves of the pandemic around the world.

High transmissibility
Delta has already spread to at least 92 countries around the world. The strain undoubtedly contributed to the massive wave of cases that has inundated India and Nepal in recent months and makes up virtually all new cases in the U.K., and about 10 per cent of recent infections in the U.S. The present scenario of transmission indicates that it may be more likely to infect people who are only partially vaccinated than other strains and may also come with a higher risk of hospitalisation owing to its high transmissibility.
The variant Alpha has been reported in 170 countries and territories, Beta in 119 countries, Gamma in 71 countries, and Delta in 92 countries as reported by the World Health Organisation (WHO) recently. The Delta variant of COVID-19, identified in at least 92 countries, is the most transmissible of the variants identified so far and is spreading rapidly among unvaccinated populations.
The WHO has warned that the Delta variant will soon become the most dominant COVID strain in the world and cause rapid outbreaks among unvaccinated susceptible populations. There are a limited number of researches regarding either Delta variant causes more severe illness than other variants. The available data suggests that Delta is more likely to lead to hospitalisation than other variants mainly due to increased transmissibility rather than it being more pathogenic.
The Delta variant is significantly more transmissible than the Alpha variant and is expected to become a dominant variant if current trends of spread continue. As some countries have eased public health and social measures, there have been rapid increases in transmission around the world. More cases lead to more hospitalisations which cause strain to already overstretched healthcare systems particularly in developing economies that in turn increases mortality.
Even though some countries have high percentages of people who are vaccinated, still the entire population of those nations is not yet vaccinated and many people have not received their second dose of the vaccine. A large majority of countries have a poor record of their vaccinated population. The virus will continue to evolve. It is well-known fact that our public health and social measures work, our vaccines work, the diagnostics work, and the therapeutics work in containing the virus spread and decreasing mortality. But when the virus continues circulating in susceptible populations, there may be a time where this virus evolves and these countermeasures do not work. Therefore, our objective in containing the virus spread is to keep transmission down and keep it down. More transmissions lead to evolution of more variants and less transmission results in fewer variants. Therefore, we should use all the tools at our disposal such as public health measures and equitable vaccination drive to prevent transmission.
The highly transmissible Delta variant (B.1.617.2) of COVID-19 is already mutated to Delta Plus. However, there is limited data on its transmissibility and pathogenicity. Full vaccination is effective against the Delta strain but maybe slightly less effective than against other variants, particularly after only one dose. It was recently reported that Pfizer’s COVID vaccine was 96 per cent effective, and AstraZeneca’s vaccine 92 per cent effective, at preventing hospitalisation from the Delta variant.
Again, as with every known variant, full vaccination works against the Delta strain and prevents serious illness at the very least. But the vaccination coverage in many countries around the globe is worrisomely low which makes the virus continue circulating among the vulnerable unvaccinated population and continue mutating and in the worst case become more virulent as well as a pathogenic variant.

Reducing spread
A variant with higher transmissibility is a great danger to people without immunity either from vaccination or prior infection. It is equally dangerous even if the variant is no more deadly than previous versions of the virus. A more transmissible variant can cause rapid spread to the immunologically naive population.
The Delta variant is proof of both how SARS-CoV-2 continues to evolve and how that evolution is continuing to produce variants that are more dangerous than their predecessor. From the available evidence, the Delta variant may be the most transmissible variant yet to spread throughout the world, and thus poses the biggest risk to unvaccinated populations, and possibly to populations who have received only one dose.
It is, therefore, important to speed up vaccination campaign. The best way to prevent new variants from evolving is to give the coronavirus fewer opportunities to mutate. This can be achieved by preventing and containing outbreaks with effective public health measures such as the use of face masks, washing hands, and avoiding crowds, and by vaccinating the majority of its population as soon as possible.

(Prof. Lohani is the founder and academic director at Nobel College. lohanis@gmail.com)