The most terrible Covid-19 variant today: Just one Delta variant is enough to make the whole world afraid

No Covid-19 variant has ever been more worrisome than Delta, which was discovered in India in February 2021. On June 21, the World Health Organization (WHO) said Delta was the "most perfect" variant to date , because it can spread more quickly and easily, while causing severe symptoms in unvaccinated people.

"Delta is a super-infectious variant, the worst version we've ever seen," said Eric Topol, director of the Scripps Translational Institute.

And it's entirely possible that Delta is the worst variant the coronavirus has ever brought us. One that epidemiologists have deemed to be the most "comprehensive."

The Delta variant has been detected in more than 80 countries.

Roberto Burioni, an Italian virologist, studied this possibility and published it in the journal Nature on June 21. In the report, Burioni said that the Delta variant has reached a threshold where it cannot evolve to become more infectious . They said that this is the "perfect variant" and will become the dominant strain, with only occasional very minor variations.

It's too early to say when the report will be published, as Delta is not yet the dominant variant globally. But it's likely to be soon, as Delta has been detected in more than 80 countries, and is still the dominant variant in the UK and India.

" Delta is moving toward a completely omnipresent form . Whether it's omnipresent is hard to say, but I don't think we're going to see much change in it," said Andrew Read, an infectious disease expert at Pennsylvania State University.

"If Delta comes out on top and nothing changes, then it's likely that for the next year or two it will be the dominant strain."

The perfect strain to spread

Coronaviruses are always evolving, but in a relatively harmless way. But every now and then, a mutation emerges that can make the virus more aggressive.

New variants can evade antibodies generated by vaccines or previous infections, making symptoms more severe and transmission easier. And Delta meets at least two of these criteria.

Delta infection doubled the risk of hospitalization compared with Alpha.

Public Health England says Delta now poses a 60% higher risk of transmission than the Alpha strain - the variant found in the UK - which is also a variant that is 50% more transmissible than the original strain.

Researchers in Scotland also confirmed that Delta infection doubled the risk of hospitalization compared to Alpha. And once again, Alpha was also determined to be 30% - 70% more virulent than the original strain.

Not yet! New evidence suggests that a single dose of the vaccine is unlikely to be as effective against Delta as other strains . But the good news is that a recent study in the UK found that Pfizer's vaccine was 88% effective in preventing symptoms of Delta with two doses, compared to just 33% with one. However, this effectiveness rate is significantly lower than the 95% for the original strain (with two doses), and 52% with the first dose.

The best way for a virus to reach full-blown dominance is to spread more quickly. If a variant spreads quickly, it won't be in a hurry to evade the body's immunity because it can just jump to a new host.

Delta is by far the most contagious variant. Delta cases in the US have tripled in 11 days, from 10% in early June to 31% of cases in the past week. At this rate, Delta will soon become the dominant strain in the US.

All current vaccines are effective in protecting people from the harmful effects of all Covid-19 variants.

And that doesn't mean the coronavirus has reached its maximum transmissibility. Read says Delta could absorb and combine mutations to become even more transmissible, creating what he calls a 'Delta-plus' variant. It's also possible that two separate variants—like Alpha and Delta—could combine to produce a more transmissible variant. Or, alternatively, a completely new variant could replace Delta as the dominant strain.

Still, vaccines — all of them — can protect us against the current variants, to avoid the worst complications.

"No vaccine has ever been inactivated," Read said.