india

Updated: Apr 21, 2020 15:20 IST

Covid-19 is not the first, nor will it be the last , of high-impact, rapidly spreading pandemics to cause disruption and death on a large scale, upend economies, and roil society. Pandemics are emerging with higher frequency and becoming increasingly difficult to contain because of a convergence of several global ecological, political, economic and social trends, including population growth, urbanisation, economic integration, faster travel, migration and climate change, experts say.

The coronavirus disease (Covid-19), which has already infected 2.4 million people and killed at least 165,000, is the second most devastating pandemic after the 1918 Spanish flu, which killed an estimated 50 million people in 11 months between 1918 and 1919. The Spanish flu also hit India hard, with the country recording its only dip in the decadal population growth rate between 1911 and 1921, when the population fell by 0.31%. This was the only decade since 1901 to date when the country’s population did not increase, according to Census of India data.

“Epidemic-prone diseases such as influenza, severe acute respiratory syndrome (Sars), Middle East respiratory syndrome (Mers), Ebola, Zika, plague, yellow fever and others, are harbingers of a new era of high-impact, potentially fast-spreading outbreaks that are more frequently detected and increasingly difficult to manage,” said The World At Risk 2019 report by the Global Preparedness Monitoring Board (GPMB). The report was authored by 15 global scientists and public health leaders, including India’s principal scientific advisor, Dr K VijayRaghavan.

The World Health Organization (WHO) tracked 1,483 epidemics in 172 countries between 2011 and 2018 and in 2019, warned that another H1N1 2009-10 influenza-like pandemic was inevitable. But instead of an influenza, what is causing havoc is a novel coronavirus, severe forms of which have had limited human-to-human transmission in the past.

The novelty of the Sars-CoV-2 virus, which causes Civid-19, and the secrecy China has maintained around it have fuelled persisting rumours about the virus being a bio-weapon that accidentally leaked from a lab in Wuhan city, where the outbreak started. Scientists, however, have used genetic material of Sars-Cov2 to establish its natural origin. “Our analyses clearly show that Sars-CoV-2 is not a laboratory construct or a purposefully manipulated virus,” according to an analysis published in the journal Nature Medicine on March 17.

Sars-CoV-2 is very closely related to Sars-CoV, but the overall genetic structure is distinct from the known coronaviruses and most closely resembles viruses found in bats and pangolins that had not been known to cause humans any harm. “If someone were seeking to engineer a new coronavirus as a pathogen, they would have constructed it from the backbone of a virus known to cause illness in human,” said the Nature Medicine study, dismissing conspiracy theories about the lab origin of the virus.

So, what makes Sars-CoV-2 different? A study of the genetic template revealed that the spike (S) proteins that cover the virus and give it its characteristic crown-like appearance, have evolved to target a receptor on the outside of human cells called ACE2, which is a key regulator of blood pressure and immunity, among others, and is found on the outer surface of cells in human lungs, arteries, heart, kidney, and intestines.

What makes Sars-CoV-2 lethal is the ease with which it spreads and the severity of disease caused by it. There are seven coronaviruses that infect humans, of which Sars-Cov, Mers-CoV and Sars-CoV-2 can cause severe disease; the other four coronaviruses (HKU1, NL63, OC43 and 229E) cause mild cold-like symptoms.

Where did the virus come from? Coronaviruses jumped from civets in Sars and camels in Mers. In the case of Sars-CoV-2, it was most likely a bat, which transmitted the virus to an intermediate animal (most likely a pangolin), from where it spread to humans.

Understanding whether the viruses’ pathogenic abilities (abilities to cause disease) evolved in animals before it started infecting humans, or occurred in humans after it jumped from its animal host, will help determine how frequently such pandemics will occur in the future. “The chances of similar outbreaks are lower if the virus infects humans and then evolve its highly pathogenic properties. The virus is not mutating fast, which offers hope for a vaccine,” said Dr NK Ganguly, former director general, Indian Council of Medical Research.

There have been thousands of outbreaks in India over the past five years, ranging from annual ones like influenza (H1N1 and H3N2), acute encephalitis syndrome, chikungunya, dengue and measles, to rarer ones like Crimean-Congo haemorrhagic fever, Kyasanur forest disease (monkey fever), nipah viral disease, scrub typhus, and zika virus disease, among others, according to the Integrated Disease Surveillance Programme under the ministry of health & family welfare.

The only way to contain health emergencies is to build infrastructure to test, contain and treat. “I believe the coming reality for the world will be one where we are always defending against this enemy. A kind of fire brigade is needed in place, and within that defence, then have the recovery of social interaction and economic activity but done in a way that keeps us all as safe as much as possible,” Dr David Nabarro, the World Health Organization’s special envoys on Covid-19, told Hindustan Times.