Latest: BA2 strain sparks urgent call for Covid vaccine for children under three
The BA.2 variant of the coronavirus is driving another surge of cases around the world, from the UK to America.
The number of people each sufferer could infect is believed to be 12, making it one of the world's most contagious diseases yet.
So why is BA.2 driving record case numbers, and are its symptoms more severe than earlier variants?
The National explains.
What is BA.2?
A sublineage of the Omicron family, which has three subvariants: BA.1, BA.2 and BA.3.
BA.1 was the one that originally took off and spread around the world, but BA.2 has gained a foothold now in many countries and is on the increase, leading to rises in case numbers.
One of the most interesting things about the three subvariants is that each is as different to the other as Alpha, Beta, Gamma and Delta are from each other.
The three Omicron sublineages, which were detected at the same time in South Africa, share 39 mutations. But each has some of their own. In the case of BA.1, there are 20; BA.2 has another 27, and BA.3 has 13 more.
BA.2 spreads faster than BA.1, about 30 per cent more according to estimates, which means it is easier to catch. Scientists think its extra mutations help to make it more transmissible.
“Omicron BA.2 is about 1.4 times more infectious than BA.1,” wrote former World Health Organisation scientist Prof Adrian Esterman on Twitter.
“The basic reproduction number (R0) for BA.1 is about 8.2, making R0 for BA.2 about 12.
“This makes it pretty close to measles, the most contagious disease we know about.”
The R0 of measles is between 12 and 18.
Are the symptoms more severe?
Studies in the UK and Denmark found no evidence that an infection with BA.2 is linked to a greater risk of being admitted to hospital than with BA.1. A more recent study from Qatar showed the same thing.
There had been some concern after an animal study in Japan found that BA.2 caused more severe disease in hamsters. But findings in animal studies do not always translate well to human beings.
New research from Hong Kong suggests, however, that BA.2 may be more severe in children than other variants.
They found the strain was associated with higher odds of paediatric ICU admission, mechanical ventilation and oxygen use.
“The intrinsic severity of Omicron BA.2 in children who had no past Covid-19 or vaccination is not mild,” the researchers said.
“And in fact … the Omicron BA.2 is more neuropathogenic than previous Sars-CoV-2 variants, influenza and parainfluenza viruses, resulting in more seizures.”
Although Omicron is milder in adults than Delta, BA.1 evades immunity from vaccination and other variants, making it easier for people who have been vaccinated to catch, particularly if they have not been boosted.
But BA.1 provides strong protection against BA.2, according to the WHO. So anyone who had Omicron earlier should be protected against BA.2.
Common symptoms of the variant include a cough, shortness of breath, loss of taste or smell, sore throat or hoarse voice, congestion or runny nose, and nausea or vomiting.
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Patients rest inside a Covid-19 isolation centre in Navi Mumbai, India. AFP -
An Israeli paramedic collects a swab sample from a child at a Covid-19 testing centre in Jerusalem. AFP -
A caricature of Serbian tennis champion Novak Djokovic looks over a market in the Indian city of Siliguri, a day after a court overturned the Australian government's decision to cancel his visa on Covid-19 vaccination grounds. AFP -
Workers spray disinfectant outside a shopping mall in Xi'an, northern China. AFP -
Women wearing kimonos and protective masks ride on an escalator in Tokyo. Reuters -
Dr Anthony Fauci speaks during a US Senate committee hearing to examine the federal response to Covid-19. AP -
A centre for filling oxygen tanks in Bangalore, India. EPA -
Medical staff dressed in superhero costumes accompany children aged 6 to 11 as they receive a vaccine at a school in Yogyakarta, Indonesia. AFP -
A shopper walks past empty frozen-food coolers at a shop in Cranberry Township, Pennsylvania. Shortages at US shops have grown in recent weeks amid supply-chain struggles and labour issues. AP -
Students and staff at the University of Southern California are required to get Covid-19 vaccine booster shots and show proof of a negative test to return to in-person classes. EPA -
A teacher takes a class remotely at Hazelwood Elementary School in Louisville, Kentucky. Getty -
Dr LouAnn Woodward of the University of Mississippi refers to a graph outlining the rising number of Covid-19 patients over a 14-day period. AP -
Medics tend to a Covid-19 patient at the intensive care unit of Cremona Hospital in northern Italy. AFP -
Pharmacy workers remove Christmas decorations from a window in Lisbon, Portugal. While Portugal has been reporting record figures of daily new coronavirus cases driven by the Omicron variant, the number of patients in intensive-care units has fallen. Bloomberg -
Students wearing protective masks study in a classroom at the Merlan school in Paillet, Ivory Coast. Reuters -
A Pakistani health worker takes a sample to test for Covid-19 during a surge in Omicron cases in Islamabad. EPA -
A general view of the Nightingale Covid-19 Surge Hub which is being erected at the Royal Preston Hospital in Preston, England. Getty -
Indian devotees walk for a health check-up at the Babughat transit camp before the Ganga Sagar annual fair in Kolkata, eastern India. EPA
Why are case numbers rising?
Partly because of BA.2’s increased transmissibility, but many countries where case numbers are surging have dropped restrictions in an effort to learn to live with the virus.
Waning immunity is also believed to be playing a factor, as protection from boosters fades and many people received theirs months ago.
Case numbers have risen fast and high in the UK, but White House chief medical adviser Dr Anthony Fauci said this week he did not expect another surge right now in the US.
However, there are signs a new wave is beginning.
Wastewater surveillance at 15 sites showed an increase greater than 1,000 per cent in the virus from February 24 to March 10.
And on Thursday, New York state reported 3,875 new cases – an increase of 87 per cent from last week.
Why is it called stealth Omicron?
It gained this nickname because it was not initially clear to labs it was of the Omicron family.
PCR tests look for three genes and with BA.1 only two react, giving labs a handy shortcut to identify it.
But BA.2 does not have this missing gene. All three can be found under examination of PCR samples of BA.2, making it look like variants, such as Delta.
Coronavirus sweeps across the globe – in pictures
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A healthcare worker prepares to administer a Covid-19 vaccine in Mogadishu, Somalia. Reuters -
Workers take samples for Covid-19 tests at a drive-through clinic in Auckland, New Zealand. AP -
A monk uses his mobile phone in Ho Chi Minh City, Vietnam. Reuters -
A man reads a newspaper next to closed shops after the government announced an island-wide lockdown in Colombo, Sri Lanka. EPA -
A woman instructs her grandson to clean his hands at the State Fair in Louisville, Kentucky. Reuters -
Medics transport a Covid-positive patient to a hospital in Houston, Texas. AFP -
Members of the security forces guard the Taj Mahal after sunset in Agra, India. EPA -
Vancouver Whitecaps goalkeeper Maxime Crepeau signs autographs before his team's match against Los Angeles FC in Vancouver, Canada. AP -
An employee stands at the entrance of a supermarket to check visitors' health app QR codes and body temperature in Shanghai, China. EPA -
A man shows the green pass on his phone before entering a shopping mall in Abu Dhabi, UAE. Khushnum Bhandari / The National
