The latest alarming coronavirus variant is exploiting low global vaccination rates and a rush to ease pandemic restrictions, adding new urgency to the drive to get more shots in arms and slow its supercharged spread.

The vaccines most used in Western countries still appear to offer strong protection against the highly contagious delta variant, first identified in India and now spreading in more than 90 other countries.

But the World Health Organization warned this week that the trifecta of easier-to-spread strains, insufficiently immunized populations and a drop in mask use and other public health measures before the virus is better contained will "delay the end of the pandemic."

The delta variant is positioned to take full advantage of those weaknesses.

"Any suffering or death from COVID-19 is tragic. With vaccines available across the country, the suffering and loss we are now seeing is nearly entirely avoidable," Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said Thursday in urging more Americans to roll up their sleeves ahead of the mutant's spread.

Amid concerns about the variant, parts of Europe have reinstated travel quarantines, several Australian cities are in outbreak-sparked lockdowns - and just as Japan readies for the Olympics, some visiting athletes are infected. The mutation is causing worry even in countries with relatively successful immunization campaigns that nonetheless haven't reached enough people to snuff out the virus.

For instance, the mutant has forced Britain, where nearly half the population is fully vaccinated, to postpone for a month its long-anticipated lifting of COVID-19 restrictions, as cases are doubling about every nine days.

In the U.S., "we're still vulnerable for these flare-ups and rebounds," said Dr. Hilary Babcock of Washington University at St. Louis.

The variants "are able to find any gaps in our protection," she said, pointing to how hospital beds and intensive care units in Missouri's least-vaccinated southwestern counties suddenly are filling - mostly with adults under 40 who never got the shots.

With nearly half the U.S. population immunized, CDC's Walensky said about 1,000 counties, mostly in the Midwest and Southeast, with vaccination rates below 30% "are our most vulnerable."

But the variant poses the most danger in countries where vaccinations are sparse. Africa is seeing cases rise faster than ever before, partially driven by the mutation, the WHO said Thursday, while areas in Bangladesh that border India are also seeing a variant-fueled surge. Fiji, which got through the first year of the pandemic without just two virus deaths, is now experiencing a significant outbreak blamed on the strain, and Afghanistan is desperately seeking oxygen supplies because of it.

The delta variant remains far from the only version of the coronavirus that's spreading - and you don't want to catch any kind. Here's what scientists know so far:

More of a killer?

Scientists believe the delta variant is about 50% more transmissible than other types. Researchers are just beginning to tease apart why. But there are early clues that some mutations may ease a key step in how the virus slips inside human cells, said Priyamvada Acharya, a structural biologist at the Duke Human Vaccine Institute.

Still, it's not clear if higher contagion is the whole reason the variant is spreading so quickly. In Britain, its rise followed a loosening of restrictions in May, when restaurants, gyms and other businesses reopened, and thousands of fans have attended sports events.

It's harder to tell if the delta variant makes people sicker. British experts have said there are some preliminary signs it may increase hospitalization, but there's no evidence it is more lethal.

It fuelled a devastating COVID-19 surge in India in February, and "this time around we had a lot more people who were very sick compared to before," said Dr. Jacob John of Christian Medical College at Vellore. But he cautioned that the "explosion" of cases didn't necessarily mean this version was more dangerous, as more cases usually mean more hospitalizations.

British researchers found two doses of either the Pfizer-BioNTech vaccine or the AstraZeneca one were only slightly less effective at blocking symptomatic illness from the delta variant than from earlier mutations - and importantly, remain hugely protective at preventing hospitalization.

But there's an important catch: Just one dose proved far less effective against the delta variant than against earlier versions of the virus. That has prompted Britain, which originally extended the gap between doses, to speed up second shots.

There's little information on whether the delta variant can escape other vaccines, such as ones developed in China or Russia.

Experts say the Moderna vaccine, the same type as Pfizer's, should be similarly protective.

Johnson and Johnson announced late Thursday that its one-dose shot also protects against the delta variant, citing lab tests of vaccine recipients' blood. In a news release, the company said the immune response lasts eight months and counting. The information comes as some people immunized with J and J's single shot have wondered whether they'd need a booster against the new mutated virus.

The mask: still your best friend

The WHO has urged governments not to lift pandemic restrictions too quickly - including saying everyone, even the vaccinated, should continue to wear masks given that the delta variant spreads more easily and no vaccine is 100% effective.

In the U.S., the CDC maintains it still is safe for the fully vaccinated to go mask-free. But there's no way to know if maskless people really are vaccinated and local governments can set tighter guidelines. This week, with the delta variant spreading locally, health officials in Los Angeles County said they still recommend masks indoors in public places for everyone.

If that's confusing, consider that the more the virus is spreading in a particular area, the more risk even the vaccinated have of getting a mild or asymptomatic infection they could spread to someone not protected - such as children too young to qualify for the shots.

In Missouri, fully vaccinated Babcock makes sure she has a mask to pop on quickly if she runs into a crowd: "I feel like my new normal is holding a mask in my hand, ready to put it on if I need it."

The Mother of All Lockdowns

In a state-run hospital near Bangladesh's border with India, Shahinul Islam prays his father does not become one of the facility's more than 300 patients who've died this month from the coronavirus.

Hundreds like his father are struggling to breathe in the COVID-19 treatment unit, while Islam waits in an emergency room packed with people. Relatives rush in and out, desperately trying to find oxygen cylinders for their loved ones.

The crowds of COVID-19 patients and worried kin are new scenes for the 1,200-bed Rajshahi Medical College Hospital, which serves border communities being overrun by the more infectious delta variant first detected in neighbouring India.

Over 450 people with COVID-19 were admitted on Tuesday to the state-run hospital in Rajshahi district's main city.

Islam said his entire family has been shunned by people in his home village closer to the border. "The other villagers are afraid of us. They don't talk to us. When they see us on the road, they take a different path," he said. "We are suffering a lot," he added.

Rising infections and crowded hospitals are being seen across Bangladesh, where a stringent lockdown starts Thursday. The government will deploy military soldiers, paramilitary border officers and riot police to enforce the lockdown, set initially for one week. Authorities warn that the rapid surge in border areas is accelerating the virus' spread further into Bangladesh, and the increasing number of infections from the delta variant could devastate the South Asian nation of more than 160 million people.

"If people do not maintain health safety rules and if they do not stay at home, this wave of the pandemic in Bangladesh could be catastrophic. It spreads fast and it kills more people," said A.S.M. Alamgir, a chief scientific officer of the government's Institute of Epidemiology, Disease Control and Research (IECDR).

Many border districts in northern and southwestern Bangladesh were spared from COVID-19 until now, so people lack antibodies against the virus. That combined with the large numbers of unvaccinated people makes the population much more vulnerable.

Just over 4 million people are fully immunized. Another 1.5 million have received one dose, but the shortage of Oxford-AstraZeneca imports, halted by India, have left them uncertain when they'll get their second dose.

The Rajshahi hospital is also short of the type of oxygen supply system necessary for critical patients at a time when it's seeing more and more patients with worryingly low oxygen levels. High flow nasal cannula delivers steady continuous oxygen to such patients, but government hospitals in border districts have been forced to rely on portable oxygen cylinders instead.

"They can't be managed properly with just oxygen cylinders. If we can't provide them with central oxygen line, God forbid, the casualties may increase," said Brig. Gen. Shamim Yazdani, director of the hospital.

Bangladesh's earlier virus outbreak caused infections and deaths to explode in crowded cities like the national capital Dhaka, but since late May, smaller towns and villages in the northern and southwestern border regions have become the major concern, said the scientist, Alamgir.

After the pandemic hit a devastating peak in April in India, Bangladesh shut the border. Still, many travelled to and from India illegally, bringing with them new infections. The situation in India has now eased, but in Bangladesh, it has only escalated.

The South Asian nation has confirmed over 900,000 cases in total, including more than 14,000 deaths since March last year while experts say the actual figures could be more. On Monday, daily infections touched a record 8,364 - almost double from last week, according to the health ministry. Sunday saw its highest reported deaths of the pandemic, 119, while another 112 people died Tuesday.

Experts are bracing for the situation to further worsen in the coming weeks. The country's vaccine supply got a slight boost with the recent arrival of another 1 million doses of China's Sinopharm vaccine, but it's still waiting on 20 million AstraZeneca doses already ordered from the Serum Institute of India. Without that order, mass vaccinations cannot begin.

The surging cases and vaccine uncertainties pushed Prime Minister Sheikh Hasina's government to double down. Restrictions began in phases Monday before all economic activity is halted in a stringent nationwide lockdown starting Thursday.

In anticipation, thousands of people attempted to flee Dhaka since last weekend, crowding bus and ferry terminals while flouting public health measures like maintaining distance.

A complete lockdown may be the only answer to slow the variant, which poses the biggest risk yet. The government is also trying to procure more vaccines, said scientist Alamgir.

"If we can enforce the strict shutdown as planned, we will be able to avoid a disaster," he added. "Let's hope for the best."

Vaccines are back

If there is a silver lining, it would have to be that things are starting to move again on the vaccine front. After initially seeming to underplay the scale of the need and urgency in Bangladesh, the Biden administration stepped up of its own accord this week to announce a very generous allocation of 2.5 million doses of Moderna's groundbreaking Covid-19 vaccine for Bangladesh. It even had them shipped out early, so that the government here in Dhaka is expecting to receive 1.2 million doses, or about half the total announced by the White House under the Covax facility tonight.

The first batch of the total 2.5 million vaccine doses, coming from the United States, is scheduled to reach Hazrat Shahjalal International Airport in Dhaka at around 11:20pm on Friday, according to Health Minister Zahid Maleque. In a media statement on Thursday, the ministry also said that the country would receive the rest of the doses - 1.3 million - on Saturday morning. It said the health minister would be present at the airport on Friday night to receive the vaccine consignment.

This one is an mRNA vaccine that has been developed by ModernaTX, Inc of the US. Bangladesh health authorities approved it for emergency use on Tuesday. This is a two-dose vaccine and administered 28 days apart. The unpunctured vials (varied from 11 to 15 doses) may be stored in the refrigerator between 2° and 8°C for up to 30 days.

The Moderna vaccine is the seventh approved for emergency use in Bangladesh. The other six are Oxford-AstraZeneca, Sputnik V, Sinopharm, Pfizer-BioNTech, Sinovac, and Johnson and Johnson.

Until Wednesday, Bangladesh administered over 10.1 million doses of the AstraZeneca vaccines since January end. Among them, more than 5.82 million people got their first dose, over 4.28 million of whom received the second jab as well.

According to the DGHS, until Wednesday, over 55,500 people received the first dose of the Sinopharm vaccine and 1,329 of them got both doses.

At the same time, some 240 people also received the first dose of the Pfizer-BioNTech vaccine, just over 100,000 doses of which arrived under Covax last week.

The health authorities also resumed the mass Covid-19 vaccination program across Bangladesh on Thursday, which will continue amid a strict week-long nationwide lockdown that started from 6am. On Thursday, Bangladesh recorded the highest number of Covid-19 deaths - 143 - since the pandemic broke out in the country in March last year. These new deaths took the national tally to 14,646 as of July 1, 2021. During the same period, another 8,301 new cases were reported across the country, taking the nationwide caseload to 921,599.