HT Explains | How the Delta variant has changed the war against Covid

The variant has meant that a year when the world hoped to leave lockdowns behind, the need for them has become more pronounced than ever, especially in regions with unvaccinated, vulnerable populations
The variant, also known as B.1.617.2, was first detected in India in late 2020. With genome sequencing of samples being scant, it is not clear how exactly it spread in the population at first, especially between late 2020 and March, 2021. (AP) PREMIUM
The variant, also known as B.1.617.2, was first detected in India in late 2020. With genome sequencing of samples being scant, it is not clear how exactly it spread in the population at first, especially between late 2020 and March, 2021. (AP)
Updated on Aug 02, 2021 02:13 PM IST
Copy Link

Last week, leaked slides from an internal US Center for Disease Control (CDC) called for a sharp change in the public messaging around the pandemic: The war has changed, people must be told.

Obtained and first reported by the Washington Post, the document outlined several features of the Delta variant, which has turned the clock back in the world’s fight against the coronavirus.

The variant has meant that a year when the world hoped to leave lockdowns behind, the need for them has become more pronounced than ever, especially in regions with unvaccinated, vulnerable populations. It has meant that despite the remarkable scientific efforts of 2020, more lives will be lost to the virus in 2021.

Ultimately, it threatens to extend vaccine inequality, as countries that can afford it are now scrambling for third shots — just when supplies seemed to be freeing up for the Global South.

To fully understand these implications, it is crucial to first recognise the biological nature of the threat, as well as the missteps that diminished the world’s ability to tackle it on time.

Unravelling the Delta variant

The variant, also known as B.1.617.2, was first detected in India in late 2020. With genome sequencing of samples being scant, it is not clear how exactly it spread in the population at first, especially between late 2020 and March, 2021.

Also Read | India records 40,134 new Covid-19 cases, 422 deaths; positivity rate at 2.81%

From March onwards, as the country held several election rallies and superspreader religious gatherings, the variant’s prevalence exploded. The reasons, apart from the human factors, are only just becoming clear. Take the following research-backed findings.

One, the CDC report says the variant is as transmissible as chicken pox and can spread more readily than the virus that caused the 1918 Spanish Flu.

Two, the report cited studies that showed vaccinated people, if infected, can pass the virus on as effectively as unvaccinated people.

Three, in China, researchers who traced and analysed samples from the first Delta variant infection found yet more worrying signs — the amount of virus found in nasal passages was approximately 1,000 times more on the first day a person tested positive, as compared to the first day of people testing positive with the ancestral variant.

Four, the Chinese researchers found that the first Delta variant case alone led to 167 more infections over the span of a month.

How did it become so serious?

First, the science of the virus. A lab study of the variant by Japanese scientists, published in mid-June, found that it led to the formation of giant infected cells – in particular because of a mutation it carries, the P681R.

The scientists determined the mutation was located close to what is known as the furin cleavage site — this works like a biological lock, with furin, an enzyme on host cell, acting as the key.

Also Read | Number Theory: Kerala’s outbreak concerning, but it is not as bad as it looks

When furin from a human cell meets this point, it causes the spike (protrusions on the virus that help it latch onto human cells) to split or cleave, initiating the next step of the infection in which the pathogen fuses into the cells. The P681R makes this process efficient.

Unlike some of the other mutations of the Sars-CoV-2 — the N501Y (the hallmark of the Alpha variant), the E484K (largely the key in the Beta variant) — the P681R was not under scrutiny until recently.

Second, inadequate surveillance and ignored warnings. The variant ripped through the Indian population before scientists had time to fully understand it.

The systemic flaws that allowed this to happen in India, to be sure, exist across the world. But most scientists saw it coming. In a blog post in January titled Musings of an anonymous, pissed off virologist, Rockefeller University virologist Paul Bienasz outlined the ways in which people and authorities in many parts of the world were taking decisions that would lead to the dangerous new mutations to arise. This including the following elements:

• Delay rollout of testing, so that the virus could spread undetected, seeding outbreaks in geographically, demographically and culturally diverse hosts.

• Implement partial and patchy restrictions on movement and social interactions, thus maintaining consistently large pools of infected individuals.

• Keep schools open… (where) diversifying viral populations are more likely to spread undetected.

• Start a rumor-mill, making full use of social media and other outlets, with topics such as masks are unnecessary or don’t work… undermining already inadequate public health measures helps keep viral population sizes large.

In a more recent take, Ravindra Gupta of Cambridge summarised how variants typically arise: “Mutation of this virus is likely a function of the number of replication cycles within an individual and at population level.”

How this changes the war

In surpassing the transmissibility and contagiousness of the ancestral Sars-Cov-2 virus, Delta variant now diminishes the efficacy of every tool that the world sharpened since the pandemic began.

Also Read | 85 cases in a day, positivity rate inches up to 0.12% in Delhi

Testing and tracing is now tougher, as Delta makes people contagious far sooner than the ancestral virus did. Treatment too is more difficult since the Delta is established to be causing more severe disease.

The variant has also reduced the efficacy of vaccines. Experts and authorities have begun discussing the need for a third booster dose to protect people, especially those most vulnerable. Some experts, such as Gupta, have called for new vaccines.

What does this mean for 2021?

Wearing masks and maintaining social distance will be must. CDC went back on a recommendation allowing people to be without face coverings if they had both doses, before it walked back on the advisory last month.

Any reduction in outbreak will now be more tentative than earlier assumed.

In terms of vaccines, Delta is likely to soon – if it has not already – launch a new scramble for improved vaccines, which could further leave the Global South at a disadvantage just when supplies appeared to be freeing up, with rich countries reaching over 50% of vaccination coverage.

To quote the Cambridge scientist cited above: “We need to re-arm ourselves because delta has immune evasion to current vaccines+higher transmissibility and mutated forms of Delta are inevitable”.

Enjoy unlimited digital access with HT Premium

Subscribe Now to continue reading
freemium
SHARE THIS ARTICLE ON
  • ABOUT THE AUTHOR

    Binayak reports on information security, privacy and scientific research in health and environment with explanatory pieces. He also edits the news sections of the newspaper.

Close Story
SHARE
Story Saved
×
Saved Articles
Following
My Reads
Sign out
New Delhi 0C
Tuesday, May 17, 2022