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Community transmission is here, what should we do?

At least 60 per cent of population should have developed immunity against the virus for onset of herd immunity

Published: 07th May 2020 05:42 AM  |   Last Updated: 11th May 2020 11:10 AM   |  A+A-

corona mask

Health Ministry said that India hasn't entered the third phase of transmission yet but cautioned to remain aware and alert. (Photo | R Satish Babu, EPS)

Express News Service

CHENNAI: There is a prevailing opinion that the lockdown must be completely lifted, and we as a society must learn to live with the novel coronavirus. Unleashing the virus on an entire population, however, could be dangerous, say public health experts. It is time to change the strategy, they say, to focus on vulnerable population instead of isolating all infected patients.  

“There is community transmission happening right now, and there is no point in locking up all infected people in hospitals,” says India’s leading epidemiologist doctor and former principal of Christian Medical College doctor Jayaprakash Muliyil. “Responsible self-quarantine is more than enough for most patients, and it’s the best strategy to follow considering that the virus is spreading rapidly.” Expressing concern over the rate of transmission in Chennai, Muliyil says the possibility of such clusters occurring across India is very high in the coming days. "This is the natural course of the epidemic. Instead of putting all our efforts on tracking and containing all positive patients, it’s time to protect the vulnerable," says Muliyil. 

Time for herd immunity?
Antivirals and vaccines are months away from hitting the market. As a consequence, herd immunity is inevitable, say experts. And our strategies, must factor this in. So, what is herd immunity? “If antibodies are found in large parts of the population, the community will offer resistance to the disease transmission at large,” doctor P Kuganantham, senior epidemiologist and a member of the State Special Task Force against COVID-19. This immunity developed in the population, which inhibits further community spread, is called herd immunity.

Usually, herd immunity is created artificially through vaccines. In this case, as there vaccines are not yet available, we are dependent on recovered and asymptomatic patients to bring about the same, say experts. Across the world, most patients who contracted the virus has shown resistance to subsequent infection. “As per our estimates, at least 60 per cent of the population should have developed immunity against the virus for the onset of a herd immunity,” says Muliyil. 

“At that point, the virus will no more have threshold host population to spread at epidemic rates. Until that happens, we should adopt every strategy in the book to ensure that vulnerable populations are not exposed it.” That does not mean lifting of the lockdown completely. It would be equal to unleashing the virus on an unprepared society wreacking havoc to the healthcare system.

The problem with herd immunity
So, how long would it take for the onset of herd immunity? That would depend on the reproduction number (R naught) of the virus. “In India the number is 2.6, closer to what was seen in China,” says doctor Carel Joseph Peravali, a public health specialist with World Vision India and a former consultant with the World Health Organization.

“This number was arrived during the lockdown,” reminds Peravali. “It can change dramatically once the lockdown eases.” Peravali points out that mortality and virulence of the virus has been ‘extremely erratic’ globally, and it’s risky to arrive at conclusions about the nature and strain found in India.

In Italy, Spain, and the UK, mortality rate is between 10 and 13 per cent. UK thought herd immunity could be a policy strategy, and is paying the price for it now, says Peravali. Herd immunity can be used as a strategy only if the mortality rate is between 1 and 2 per cent. The mortality rate in India, as on Sunday before the lockdown was eased, was around 3.2 per cent.  

The road ahead
“Our initial strategy was to isolate the infected. Now, we must focus on isolating the vulnerable,” says doctor H Kolandasamy, who recently retired as the director of public health in TN. “Senior citizens and those with co-morbid conditions must be isolated at least for two months after the lockdown has ended.” State governments must ensure that all its healthcare and frontline workers are young, healthy, and free of co-morbid conditions.

Kolandasamy says that installing handwash facilities with soaps in all public places including bus stops and government buildings is the need of the hour. "Unwanted gatherings like birthday parties should be avoided. People should deal with any gathering the same way we deal with funerals. Bathe after coming home. Introduce thermal scanning in all buildings. If you have cold or cough, just stay home. You're not a hero for showing up at work sick," he asserts.

“The focus initially for Tamil Nadu was people coming from abroad, then those coming from Delhi, then Koyambedu... Soon, the battle will be in small pockets.”

Shifting focus
Instead of putting all our efforts on tracking and containing all positive patients, it’s time to protect the vulnerable, says the epidemiologist

Prerequisite
At least 60 per cent of the population should have developed immunity against the virus for herd immunity

1.Herd immunity is created artificially through vaccines.
2.Vaccines are not yet available for coronavirus. So we have to depend on recovered and asymptomatic patients.
3.Across the world, most patients who contracted the virus have shown resistance to subsequent infection.
4.As per our estimates, at least 60 per cent of the population should have developed immunity against the virus for the onset of a herd immunity.
5.‘Community transmission is happening right now. No point in locking up all infected people in hospitals. Responsible self-quarantine is more than enough for most patients.’
6.Instead of putting all our efforts on tracking all positive patients, it’s time to protect the vulnerable.

How long will it take for the onset of herd immunity?
it Will depend on the reproduction number (R naught) of the virus  IN India the number is 2.6, closer to what was seen in China

More from Tamil Nadu.

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