New Delhi, Bengaluru: Despite being home to one-fifth of the world’s population, South Asia accounts for less than 35,000, or approximately 1.5 per cent, of the 24 lakh coronavirus cases worldwide.
The eight countries, which make up the Indian subcontinent and are part of the South Asian Association for Regional Cooperation (SAARC), include Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka.
While the number of cases in Europe and North America was 14 lakh and 8.8 lakh, respectively, as of 22 April, India had 20,178 cases, Pakistan 9,749, Bangladesh 3,382, Afghanistan 1,092, Sri Lanka 321, Maldives 108, Nepal 42 and Bhutan 6.
Even the positivity rate — the ratio of confirmed cases to total tests conducted — is lower in South Asia. The rates in India (4.36), Bangladesh (11.43), Pakistan (8.26) and Sri Lanka (4.19) are way lower than those for Italy (12.69), US (19.55), France (34.09) and Germany (8.59).
Experts have offered different reasons to explain this disparity — the warmer and more humid weather in the South Asian region tempered the spread of the disease, protection offered by the tuberculosis vaccine bacillus Calmette-Guérin (BCG), a potentially better immune response among those in the Indian subcontinent, and a weaker strain of the virus here.
Some say the explanation could be a lot simpler — South Asian countries have likely implemented efficient physical distancing thanks to a slower first wave of spread within the countries. The nations are also reportedly seeing far lower testing numbers as compared to the rest of the world.
Low testing does not fully explain it
The SAARC countries have the lowest testing rates in the world but that may not fully explain the fewer cases.
India, for instance, conducts just 335 tests per million population whereas the numbers for western are far higher — 7,103 in France, 20,629 in Germany, and 12,659 in the US.
But even in countries of South Asia that have higher testing, the positivity rate has remained low. Bhutan has conducted a total of over 8,700 tests, which translates to 11,000 tests per million people, but has only six confirmed cases. The Maldives is currently conducting 6,871 tests per million with 1.08 positivity.
“At this point in time, no one has an explanation for the low prevalence of cases in this region,” said Sumanth C. Raman, a healthcare domain consultant and a doctor specialising in child health. “Certainly the rate of testing is lower, and that is a very likely contribution to the explanation. But it doesn’t explain the full picture.”
The lockdown may have “shifted the peak from say April to June” but only time will tell if South Asian countries indeed have an advantage, said Shahid Jameel, a virologist who serves as the CEO of The Wellcome Trust/DBT India Alliance, an independent nonprofit that funds health and biomedical research in Indian institutions.
“It (the number of cases), however, has definitely proven the doomsday predictors wrong. They had predicted the number of infected as high as 1-2 crore,” he said.
The low number of cases, some experts say, could also be the impact of early and stringent lockdowns imposed by South Asian countries.
India declared a three-week lockdown starting 25 March that has been extended to 3 May. Similar lockdowns were announced in Pakistan, Bangladesh and Sri Lanka.
By contrast, most of the states in the US, one of the worst-affected countries, enforced stay-at-home orders around late March and early April. As of 2 April, 90 per cent of the country was in some kind of lockdown. The US has recorded 8.69 lakh cases and 49,963 deaths — the highest in the world.
Some European countries like Sweden do not even have a complete lockdown, although they enforce mandatory physical distancing while keeping most public places shut.
India, on the other hand, had already shut its international flights by 25 March, which the UK and US had not done despite recording more cases. India’s lockdown stringency score was 100 as against 64.5 in the UK and 76.1 in the US, according to an analysis by researchers from the University of Oxford.
The lockdown appears to have slow down the number of cases, with the doubling rate now at 7.5 days instead of 3.4 days before, said the Union health ministry earlier this week.
India’s response in containing the epidemic has been remarkable thanks to its strong district and municipal administrative structure, said Shailaja Chandra, former chief secretary of Delhi and a public health expert. “No other country has managed to contain the spread on the scale that India has, when compared to our population density and distances involved,” she said.
She added that while the system does not always deliver during normal times, it has responded during a crisis, as always, and was able to screen, isolate cases, trace contacts and seal off hotspots because of the tenacity of the municipal, district and police systems.
Even among other countries within South Asia, there is a trend of the disease making a later appearance than usual, which ensured better preparation. Bhutan and the Maldives had their first confirmed case only in the first week of March, when the world was well aware of the nature of this pandemic and how to slow its spread.
Sri Lanka’s first recorded Covid-19 patient was a tourist diagnosed at the end of January, but, since then, strict quarantine measures were imposed across the country. The first confirmed case of a Sri Lankan national came in March.
A younger demographic
A major reason for the observed pattern of spread could be the fact that older populations respond poorly to Covid-19, said Madhukar Pai, director of Global Health at McGill University, Canada, and a tuberculosis expert. “Countries with younger populations should have a different epidemic curve because of the age effect, especially for deaths due to Covid-19,” he said.
Younger people have mild or asymptomatic infection and, over time, they will protect others through herd immunity, Pai said.
The average age of an Indian is 26.8 years. The number is under 25 years in Bangladesh, Nepal and Pakistan. In contrast, the average age of a citizen is 45 in Italy and above 40 in Germany, France and the United Kingdom.
While almost one-fourth of Italy’s population is aged above 60 years, just 7.4 per cent of Indians are senior citizens.
“There is a lot of uncertainty. Is it possible that maybe the virus is mutating rapidly enough for receptors in this population to bind differently? We don’t know yet,” Suman said. “Since obesity seems to contribute so much to hospitalisation among the younger population groups, is it related to BMI (body mass index)? Maybe there are more mild and asymptomatic infections here as compared to other places? We just don’t know.”
Variations in immune response
“Of all the theories about weather, BCG vaccine and whether India has a weaker strain, I only believe the one about immunity,” said Jameel, referring to the as-yet-unproved theory that the residents of the Indian subcontinent might be naturally equipped to fight the SARS-CoV-2 virus better than others.
“Indians and South Asians are exposed to more germs and infections, and hence their innate immune response is better,” he added.
Narinder Mehra, ICMR national chair and former dean of the All India Institute of Medical Sciences, New Delhi, is also of the opinion that Indians are exposed to more pathogens and hence have a broader T-cell memory.
T-cells are the white blood cells that fight infections, and they “remember” exposure to viruses in the form of instructions that trigger an immune response when a virus is recognised.
There is also greater variation in the human leukocyte antigen (HLA) genes, which make up human tissues and are responsible for immune response. It is these genes that present the foreign antigens to the immune system triggering the T-cell response.
“As a consequence of microbial load, the Indian population possesses a high genetic diversity of HLA, much more extensive than Caucasian populations,” Mehra wrote in a column earlier this month, referring to increased prevalence of endemic and non-endemic disease in India.
This genetic diversity has been shown to offer protection against viruses by some studies, he explained, while clarifying that “much more extensive research is required” before concluding that it offers benefits.
However without evidence, this is purely speculation that can only be confirmed (or disproved) after the results of rapid antibody tests come along. These would show whether a higher-than-expected number of individuals has antibodies to the virus, thereby confirming their exposure. If more people are exposed, and did not show symptoms or do not yet, this may prove that our immune response has been better, Jameel explained.
Pai disagreed with the immune response theory, saying it is hard to justify it with data, considering India has the highest burden of tuberculosis, Kala azar and the fourth highest malaria incidence in the world.
“There is lots of speculation from all quarters,” said Raman. “People say malaria-endemic countries could be seeing less Covid-19, but Singapore was once a malaria-endemic country too. There is no documented study that establishes that any of these hypotheses, like endemic malaria or BCG vaccination, could be an explanation.”
Subcontinent yet to peak
Jacob John, one of India’s most renowned virologists and the former head of the Indian Council for Medical Research’s (ICMR’s) Centre for Advanced Research in Virology, believes we cannot compare present-day South Asia with Europe because we are a month and a half away in terms of timeline.
While India did record its first case on 30 January, the total number of Covid-19 patients was restricted to three for a month. John said the disease truly spread in India only in March, when cases started climbing in the very first week.
After its first case, India issued advisories for screening and quarantining travellers from China in early February, while the next set of advisories, for South Korea, Iran, Italy and Japan, came on 3 March.
There, however, weren’t any restrictions on those coming from the West — the Middle-East, Europe and North America — until 18 March, which is where most Indian travellers got their infection from, said John.
Among European countries such as France, Italy, and Germany, all of whom confirmed their first cases in the same week as India, the numbers rose steadily in March and increased exponentially in April — a pattern similar to that in the subcontinent.
“We have to wait a month and half before we say anything,” said John, adding that the April of Europe should be compared to June in India.
Pai agreed that the epidemic was evolving in different countries at different times and we need to wait for the epidemic to mature. The middle-income countries that didn’t see a spike last month are doing so now, said Pai, citing India, Brazil, Peru, Ecuador, South Africa and Indonesia as examples.
While India and other South Asian nations may seem to have warded off the immediate danger of an overwhelmed healthcare network, the pandemic and the lockdown have harshly affected the economies and the poorest in the region.
Additionally, as the pandemic spreads with the potential to wreak havoc, more and more unproven treatments stemming from these observations will start being tested, which may possibly endanger lives.
According to public health experts, there is no evidence to indicate that any such correlational pattern can mean that the South Asian population is at a lower risk of decimation if physical distancing measures are lifted. If anything, any advantage conferred upon the population would only aid in slowing the spread of the disease, not averting it, they said.
“The way respiratory viruses like the novel coronavirus are transmitted in various regions does not differ,” said Wafaa El-Sadr, director and professor of epidemiology and medicine, Columbia University, New York. Around the world, observations and studies have unanimously indicated that the virus is primarily spread through respiratory droplets containing the virus, as well as through close contact with carriers.
“We cannot depend on herd immunity through continued transmission as this novel coronavirus has a high mortality rate, almost ten times higher than mortality from seasonal influenza,” El-Sadr added.
“What everyone is doing now is akin to the old anecdote about knowing that one woman can deliver a baby in nine months and thus getting nine women to deliver a baby in one month,” said Raman. “We just don’t have enough information. Many more studies are needed before we can say anything conclusively. Maybe in six months to a year, we will be able to say more definitively how the disease spreads in the South Asian population. But at the moment, everything is pure conjecture.”