- [Narrator] A COVID-19 variant first detected
in India in October of 2020
has quickly spread around the world
and been detected in nearly 100 countries
within 10 months.
As of July, more than 80% of known COVID cases
in the US are caused by the Delta variant.
- The Delta variant is currently the greatest threat
in the US to our attempt to eliminate COVID-19.
- The Delta variant is both more transmissible
and possibly more severe.
- [Narrator] Studies have shown that some COVID vaccines
are effective at preventing symptomatic illnesses
caused by the strain.
Nevertheless, as of July,
cases are on the rise in countries
where a large part of the population is vaccinated.
Even countries that have been previously spared
from the pandemic are now battling
a ferocious wave of infections.
We look at some moment in key countries
to understand why the deadly outbreak of Delta
is not just threatening the economic recovery
but also the return to normal around the world.
First, we go back to October of 2020.
Health authorities say the Delta variant
was first detected here in the state
of Maharashtra in India.
By the spring, the number of cases in India
began ticking up.
Then from March to May,
infections jumped 20-fold,
plunging the country in disarray.
- [Betsy] It ripped through the country.
Thousands and thousands of new infections every day.
Hospitals were completely overwhelmed
and they were running out of oxygen
for patients who needed help breathing.
(speaking in foreign language)
- [Narrator] Public health experts blamed
India's deadly wave on several factors.
There were political rallies for state elections
that drew large crowds.
There was also a religious festival in April
when millions of Hindus gathered to bathe
in the Ganges River.
And then a few days later,
the government relaxed safety measures
like mask wearing and social distancing.
But scientists say
what really helped accelerate the case load
was Delta variant's molecular composition
and its nine key mutations in the protein spikes
that surround the virus.
Mutations on these spikes allow the varies
to invade human cells more easily,
making the Delta variant about 50%
more transmissible than others.
By June 1st, the variant wasn't only in India
but detected in more than 60 countries.
And the United Kingdom
was one of the first Western countries
to see an alarming increase in cases
as Delta became the dominant strain.
- We're seeing cases growing by about 64% per week
and in the worst affected areas,
it's doubling every week.
- [Narrator] What surprised health officials
was that around 75% of the adult British population
had already received at least one dose of a vaccine
and about 50% was fully vaccinated.
- The UK's a really unfortunate situation.
There are good levels of vaccination there
but the variant took off anyway.
- [Narrator] And that was partly because vaccines
were reacting differently to Delta
than they had to earlier strains.
By mid-June, studies showed
that one dose of some vaccines
was 17% less effective
at preventing symptomatic illnesses caused by Delta.
But two doses provided good protection.
- The more the Delta variant is allowed to spread,
the greater the risk of mutations,
which would evade the vaccines or evade treatments.
And we'd kind of almost be back to the beginning.
- [Narrator] By late June,
Delta was detected in countries
that had been slower to vaccinate,
in part because they had been spared the brunt
of the pandemic
and cases began rising in these places.
Australia and Thailand imposed lockdowns.
Even Japan decided to ban spectators at the Olympics
because of a new wave of infections.
- There are many, many, many countries
that don't have access to vaccine yet.
Not many people in the population are vaccinated.
And this is the huge concern about this variant.
That it's just going to rip through these countries.
- [Narrator] Meanwhile, in the US,
as people headed into their 4th of July weekend,
the Delta variant had become the dominant strain.
People were traveling again
and many stopped wearing masks
after the CDC said it wasn't necessary
for those who were fully vaccinated.
The variant has mostly spread to areas
where vaccination rates have been slow.
In some parts of the country,
like in Los Angeles, authorities have asked people
to wear masks in indoor public places,
regardless of vaccination status.
But some public health experts say the appetite
for another lockdown is low.
- It's difficult to ask people
to once again adopt these measures.
The message is everybody needs to get vaccinated.
- [Narrator] So on July 4th, Biden urged people
to do just that
as the administration planned
to make it easier for people to get their shots,
like sending more mobile clinics to festivals
and sporting events.
- While the virus hasn't been vanquished,
we know this,
it no longer controls our lives.
It no longer paralyzes our nation
and it's within our power to make sure it never does again.
- [Narrator] And that means it's a race against time
to vaccinate more people around the world
before the coronavirus mutates against.
(lively music)