Highlights
- The COVID-19 Delta strain’s “spread power” is going global, based on new reported infections.
- Prior “variants of concern” — Alpha, Beta, Gamma — never achieved the same global dominance.
- Africa, and countries where vaccination levels are low, seen facing Delta's wrath.
Dubai: The Delta variant, first seen in India, is now dominant in most continents. In Africa, Delta accounted for more than half of the continent’s COVID-19 cases last week.
Even as vaccine doses have topped 3 billion around the world, the growing dominance of Delta, has kicked up concern. The strain is now spreading rapidly, seen behind new infections in nearly 100 countries, according to the World Health Organisation (WHO). The variant — 60% more contagious than Alpha (first seen in the UK) — seems to be fuelling illness among young adults, according to one report. Following are the updates:
Does the Delta variant cause severe COVID-19?
It’s not clear at this point. There’s still little data available about whether the Delta variant causes more deaths. Three points to consider:
First, WHO scientists say more research data are needed to confirm if Delta causes more severe cases than other known variants.
Second, there are signs the Delta strain could trigger different symptoms than other variants (Alpha, Beta, Gamma).
Third, leading experts say Delta’s "super-spreader” status does not mean conferring it “super-virulence”. On the contrary, there are signs Delta infections are getting less severe (lesser deaths), even as the virus becomes more “fit”.
What is the Delta variant?
The Delta variant, first reported in India, is considered a “superspreader” strain of SARS-CoV-2. It’s one of four “variants of concern” (VoC) identified by WHO. There’s growing evidence Delta is going global.
Prior variants of concern — Alpha (UK), Beta (South Africa), Gamma (Brazil) — never achieved the same global dominance. This demonstrates the “spread power” of this strain.
Where is Delta gaining dominance?
The growing dominance of the Delta variant is beyond doubt, it has been recorded in nearly 100 countries as of July 1, 2021. It’s rising even in countries with high levels of vaccination.
Delta is responsible for most new COVID-19 infections in Australia, India, Israel, Russia, Singapore, South Africa, Indonesia, the Philippines, the UK, the US, many other countries.
In Europe, Delta is responsible for a new rise in cases, after weeks of decline.
The WHO projects that Delta will become dominant strain by August.
What’s the evidence that Delta is gaining 'superspreader' status?
In the UK, where the already highly transmissible Alpha variant first emerged, new cases seen are 99% Delta, according to the Public Health England. The European CDC projects that Delta will account for 90 per cent of new coronavirus cases in the continent by the end of August. The US CDC reported that Delta accounted for 26 per cent of new COVID-19 cases up to June 19 in the US. In Israel, Delta now accounts for 45 per cent of new cases, though there’s been only a small spike in cases by absolute numbers.
In California, Delta accounts for 30 per cent of new cases, even if vaccinations are fairly high (>61 per cent of population had 1-dose or more). Cases in California have started to creep up again, 17 per cent in the past two weeks — (and that with 62 per cent less testing).
What are the unique mutations seen in the Delta variant?
Unique mutations are found in several places in the SARS-CoV-2 “spike” or exo-protein not seen in Alpha, Beta and Gamma (P681R and N-terminal domain, or NTD). The main mutation sites are found in the following:
- 484 and N501Y of the receptor binding domain (RBD), which binds to the ACE2 receptors on the surface of human cells, letting the virus latch on.
- NTD: N-terminal domain, which supports and stabilises the RBD. Mutations here can loosen up neighbouring lumps of protein to facilitate tighter binding.
What can be done to check Delta?
Health experts say mitigation measures like social distancing and quarantines do work.
But these are only temporary solutions. “You’ve got to get the vaccine production and equity across the globe as quickly as possible, especially the vaccines that suppress spread and have a really high efficacy,” Dr Eric Topol, professor of molecular medicine at Scripps Research, told CNN on Thursday (July 1, 2021).
Why do viral variants keep emerging?
For the first time, the world today is witnessing an almost day-to-day evolution of virus “as it happens.” This is due, in a big way, to huge advances in genome sequencing technology, and the availability of inexpensive but powerful computers.
Evolutionary virologists explain that the “progression” of variants demonstrates the virus’s drive for heightened “fitness”. It’s part of the so-called “natural selection” of mutations and strains that make it more likely to find hosts.
If Delta is highly transmissible (infectious), does it mean it’s also gaining virulence (ability to cause disease/hospitalisations)?
Not necessarily. Renowned epidemiologists Roberto Burioni and Eric Topol, in a joint article published in Nature Medicine on June 21, 2021, wrote that enhanced transmissibility would be considered the most potent path for the virus to become more “fit and viable”.
This means that, as virus evolves, it “learns” to trade-off infectiousness with lethality in order to reach “peak fitness”. So while it is becoming more infectious (highly transmissible), it’s getting less lethal.
It’s a trade-off that unfolds in the evolution of viruses. Over time, as viruses acquire the ability to become more transmissible, they tend to lose “immune-evasion” (ability to evade immunity induced by vaccines or earlier infection) or greater lethality.
Q: Will new variants emerge?
In general, more-fit variants can be expected to emerge over time, say experts. The difference today is that, given the greater collaboration and vigilance of scientists from various disciplines — including phylogenetics — any mutations or occurrence of new variants will be identified almost immediately.
Any minute changes in behaviour of the coronavirus is now subject to scrutiny at the DNA level now, more than ever.
Going forward, such mutations will need to be monitored meticulously, as these pose a potential public health threat.
Will the coronavirus mutate indefinitely?
In their Nature Medicine article, Burioni and Topol explained: “We believe that these will not continue to emerge indefinitely: nothing is infinite in nature. Eventually, the virus will reach its form of “maximum transmission”.
After that, new variants will provide no further advantage in infectivity, they said. The virus will thus “stabilise” — and this “final” variant will prevail and become the dominant strain, experiencing only occasional, minimal variations.
Do available vaccines work against Delta and other variants?
Yes. The most-potent vaccines seem to dramatically hinder viral replication and transmission. There’s no evidence of known variants emerging with the ability to completely break through vaccine-induced immunity.
What are we to do now?
There’s evidence to show it's best for people to adhere to mask and social distancing mandates to avoid the spread of infections, until everyone gets vaccinated. Premature opening, or spectator sports, are emerging as possible superspreader events.
As for vaccines, there’s no doubt the approved shots do curb severe cases. Evidence shows that immunity induced by vaccines is more potent than that elicited by the infection. Experts argue that the key to the COVID-19 fight is the prompt availability of vaccines.
As such, they would still replicate in the vaccinated hosts in communities in which the proportion of vaccinated people is high (e.g., Israel and the United States). This is the reason why Delta must be checked.
What’s the evidence that vaccines work, even against Delta?
UK, Israel and the US are cases in point. In the uK, Delta accounts for 99% of cases. In Israel, Delta now accounts for 45% of new cases, though there’s been only a small spike in cases by absolute numbers. Data available so far indicate the vaccines used in these countries seem to work in reducing severity, hospitalisation.
What’s the status of Africa vis-a-vis the Delta variant?
Coronavirus cases in Africa are rising quickly that the continent will soon face its “worst week” since the pandemic’s start, say officials.T he head of DR Congo's COVID flight warned Thursday of “catastrophe” given Delta’s rapid spread in the country, saying hospitals were already overwhelmed and morgues “overflowing”.
Almost 202,000 new cases of the illness were reported in the past week, and infections are doubling every three weeks, WHO Regional Director for Africa Matshidiso Moeti said in an online briefing Thursday.
"The speed and scale of Africa's third wave is like nothing we've seen before," Moeti said. "The continent is on the verge of exceeding its worst week ever in this pandemic."
14
African nations are facing a resurgence of the virus, 12 of which have detected "variants of concern," including nine with the Delta variant, she said. Africa is the world's least-vaccinated continent.
What if new variants escape immunity conferred by vaccines or prior infection?
Evolutionary virologists believe complete or nearly-complete resistance to the current vaccines is an “inevitability” — and this may happen some time in the future. While this possibility cannot be ignored, man’s ability to fight back — by tweaking existing therapies or vaccines — cannot also be discounted.
