There has been no respite from efforts to keep coronavirus infections at bay for close to 15 months now.

But increasingly, it is becoming clear that the bewildering array of Covid-19 variants sweeping the region will keep those tracking its spread busy for quite some time more.

The fresh new waves of infections are also stoking fears that if transmissions escalate dramatically, new super-spreader variants may emerge that could bypass ramparts offered by current vaccines, overwhelm regional health systems and lead to many more cases.

In recent weeks, reports of a surge in new cases have been emerging from several economies, with South Asia raising the most concern. Besides India, which is grappling with close to 400,000 new cases a day, Nepal, Pakistan, Sri Lanka and Bangladesh have reported sharp increases in the number of new infections.

In South-east Asia, the Indonesian government took a last-minute decision on May 6 to halt people from travelling in urban areas during the Idul Fitri holiday, as Covid-19 infections surged. Still, numbers spiralled to nearly 5,000 daily cases this week, taking the overall number of cases to more than 1.7 million. Malaysia, meanwhile, commenced its third lockdown on Wednesday (May 12).

Elsewhere in the region, Japan's hospitals in some areas have been working to full strength as the nation grapples with its fourth wave of infections and Tokyo, Osaka, Hyogo and Kyoto prefectures' third state of emergency, which has been extended by about three weeks till the end of the month. Seoul, meanwhile, is staring at a fresh new wave with cases of variants emerging among those infected.

The spiking cases across the region are worrying observers. The World Health Organisation's (WHO) data analysis shows that nearly 52 per cent of the new infections and 32 per cent of the new deaths in the seven days to Sunday came from the regions it defines as South-east Asia. The countries covered are Bangladesh, Bhutan, Democratic People's Republic of Korea, India, Indonesia, Maldives, Myanmar, Nepal, Sri Lanka, Thailand, Timor-Leste. In contrast, 23 per cent of the total new infections globally came from the Americas and 17 per cent from Europe, during the same period.

The Sars-CoV-2 virus, which causes Covid-19, accumulates mutations - or changes to its genetic code - as it replicates, much like other viruses. Most of these mutations are not of significance, but some virus variants cumulate several mutations that make these variants more transmissible and/or cause more severe symptoms.

"The more the virus circulates, the more chances it has to mutate," Dr Poonam Khetrapal Singh, WHO's regional director (South-east Asia), told The Straits Times.

"Our best chance against these variants is to limit the spread of Covid-19," she said.

With the emergence of the more serious variants of concern (VOCs), WHO has stepped up efforts to set up systems to quickly identify and study them. On March 29, a global consultation was held on the impact of virus variants, with a focus on vaccines.

"We are working with the scientific community to encourage wider sharing of sequences along with their metadata," said Dr Singh, adding that WHO also keeps countries and the public updated on learnings about the variants.

Such metadata includes important epidemiological, clinical and other information on the patient.

"Virus variants need a quick and coordinated global response," she added.

The variant detected in India

Right now, however, the regional response seems far from quick and coordinated, as national health officials scramble to contain the pandemic now exacerbated by variants and mutants.

The variant causing much distress currently is the B1617 variant first detected in India in October last year.

WHO data, as at Tuesday, shows that it could be circulating in at least 49 countries.

Within Asia, Thailand and the Philippines this week became the latest countries to report the presence of the B1617 variant. Thailand said that a 42-year old pregnant woman who arrived from Pakistan on April 24 had contracted the variant, which was also detected in two Filipino workers who had returned from the United Arab Emirates sometime last month.

Three sub-lineages of the variant have also surfaced.

Bangladesh's Daily Star newspaper said that at least two sub-types of the B1617 variant had been found in the densely populated country, and these seemed to be spreading far more quickly than those being tracked by scientists in India.

Besides the B1617 variant, variants detected last year in Britain, South Africa and Brazil continue to circulate in several locations, together with several other strains, leading experts to call for more vigilance to prevent situations similar to India from emerging elsewhere. Cases tied to all four variants have been found in Singapore.

"Surveillance of virus variants is important for situational awareness," said Professor Benjamin Cowling, the head of the Division of Epidemiology and Biostatistics at Hong Kong University.

"Some variants have increased transmissibility or severity and therefore pose a greater risk to public health," he said.

There are now four variants in circulation that are deemed more serious.

The variant first detected in Britain in September last year, or the B117, seems to have spread the most across the world.

WHO data shows its presence in 137 countries as at Tuesday, with 12 under verification.

Such has been its transmissibility that it is now the dominant strain in the United States after being detected there only a few months ago - in December last year. The American bi-weekly Scientific News reports that detailed examinations are showing that it is 50 per cent to 70 per cent more transmissible than the other strains of the coronavirus and has also been found to be more lethal, raising the risk of death overall by 60 per cent.

In India, this and the B1617 strain are the most prevalent, according to WHO.

Elsewhere in the region, it has also been causing much anxiety in countries such as Thailand, Pakistan and Japan.

Thailand, like Vietnam, seemed to have coronavirus infections well under control a few months ago. But it reported the appearance of the British variant on April 1 and has been caught up in a third wave since, with celebration of the Songkran festival further flaming the number of infections. Cases linked to this variant accounted for nearly half the total number of 72,788 cases and 303 fatalities, as at May 4.

In Pakistan, nearly 70 per cent of the 854,240 infections reported as at last Saturday were linked to the B117 variant.

In Japan, the N501Y mutation of the so-called British variant - also found in strains detected first in South Africa and Brazil - is believed to be the cause for many of the new infections in the country. According to the Japan Times, in Osaka, the N501Y mutation had pushed the occupancy rate of beds for severely ill Covid-19 patients to 99.7 per cent as at May 3, while more cases linked to this mutation were being reported in Tokyo.

"The Sars-CoV-2 virus, which causes Covid-19, will be with us for the foreseeable future," noted a spokesman for the Western Pacific office of WHO, that monitors cases in Japan and several other locations in Asia.

"The VOCs highlight the need and importance of solidarity and collective action nationally, regionally and globally," the spokesman added.

Suppressing the virus

Suppressing the virus requires public health measures, rolling out of vaccines as quickly and equitably as possible, and scaling up vaccine manufacturing.

In reality, Asia is struggling to do all of that.

Vaccination rates across the region remain far from desirable. Years of neglect of the healthcare system is showing up in several locations, while countries, struggling to calibrate the balance between containing the pandemic and sustaining livelihoods, are finding it difficult to enforce hard lockdowns to halt transmissions.

Globally, controlling transmissions is paramount, and it is not enough to rely on vaccinations, said Professor Dale Fisher, a senior infectious disease consultant at the National University Hospital in Singapore.

Variants emerge where transmission rates are high. This threatens the effectiveness of vaccines and immunity from past infection.

"There are lots of reasons why increased transmissibility can mean more deaths without the virus being more virulent," he told ST.

Large case numbers can cause hospitals to become overwhelmed, making it difficult to treat people in the way they normally could.

"Once you get overwhelmed, like in India, and hospitals run out of oxygen then you can die when under normal circumstances you could be saved."

There are also other concerns about whether the new variants could escape treatment.

Prof Fisher said the region did very well in the first year of the pandemic through a variety of strategies.

"Many relied on border controls to keep the virus out, combined with focused lockdowns and mass testing when cases did appear. Others managed a steady number of cases which were not enough to overwhelm hospitals and they protected vulnerable populations."

Compared with situations witnessed earlier in Italy and Spain, several countries had succeeded in keeping the number of infections and deaths relatively lower. But given the changing nature of the virus, it cannot be said with certainty that this will remain the case, he said.

Hope rests on ensuring that the key public health measures remain in place.

Dr Singh said: "Testing, tracing, isolating and treating, along with physical distancing, hand hygiene, cough etiquette and masks continue to be our tried-and-tested measures to curtail transmission of both the Covid-19 virus and its variants.

"People must follow this Covid-19-appropriate behaviour regardless of whether they have been vaccinated or not."

Alongside, "coordinated action on strain surveillance, collaboration among vaccine development, research and vaccine manufactures along with access to vaccines by all countries are essential for getting ahead of the virus", she added.