Covid-19: India has done well so far, but it is not advisable to lift the blockade – analysis
The Chinese government alerted the World Health Organization (WHO) to several cases of coronavirus disease (Covid-19) on December 31, 2019, and reported the first death on January 11. India discovered her first case a month later (January 30) and had her first death two months later (March 11). It is clear that Covid-19 has been largely driven by person-to-person transmission, forcing public health officials to advertise social distancing as an effective way to reduce reproductive numbers of the virus (known as R0 and pronounced as R nothing), that is, the average number of new infections generated by each infected person.
For the epidemic to begin to end, the rate of reproduction has to drop below one. Based on a mathematical model, an article by several authors published in the March 16 issue of Science warned that undocumented infections are responsible for nearly 80% of all documented cases in China, and that this single factor could facilitate the rapid spread of the coronavirus. People with undocumented infections often experience mild or no symptoms and may go unnoticed by the health system, increasing the risk of the virus spreading.
During the first half of January, before China imposed a complete blockade on the affected province, the R0 of the virus had risen to 2.38, indicating high sustained transmission capacity. China was quick to announce a full shutdown on January 23. Subsequently, R0 plummeted below one, suggesting containment of the epidemic with only a marginal increase, if any, in new infections and new deaths for weeks. This is the basis of a blockage.
However, what is unclear is the length of the period for these measures to remain in place to keep R0 infection below one for a reasonable period and to prevent possible rebound after control measures are relaxed. Do regional and population-specific factors play a role in this?
India imposed a similar blockade on March 22, exactly two months after Wuhan, first as a curfew by a village on an experimental basis, quickly followed by a national blockade starting on March 25. Now two questions are asked: First, did India manage to contain the disease as effectively as China? Second, India has a prevalence of tuberculosis, and persistent BCG vaccination has helped stimulate robust and adaptive innate (pre-existing) immunity in the Indian population. So will this broad-based immunity help India resist Covid-19?
A data analysis, through April 8, reveals interesting trends. With over 120,000 tests performed, the positive case rate in India with densely populated regions is 4.5-5.0%, compared to much higher figures in European countries and the United States. India has not yet started testing groups with high Covid-19 rates. However, according to the expanded testing standards, the low positivity rate is encouraging. What is even more remarkable is the near lack of severe and critical cases and limited mortality.
But then India is not China or Europe, where the majority of infections and deaths are concentrated in the aging of the population. The Ministry of Health and Family Welfare has presented a number of interesting figures. According to global patterns, 73% of Covid-19 patients in India are male and about 40% are in the 20-40 age group. But only about 17% of patients are senior citizens (60-80 years), although there is a higher proportion of deaths among them. These are the documented numbers and perhaps community surveillance through rapid antibody tests will shed more light on the still undocumented numbers and challenge the trends observed so far.
How does the host’s immune system recognize the virus as an enemy and eliminate it? Once the lymphocytes recognize the virus as foreign, the foot soldiers in this fight (cytokines) mobilize. They fired a cascade of signals to kill T cells for an effective response. In general, the stronger this immune response, the quicker the chances of foiling an infection. That is why younger people are still less vulnerable to the coronavirus. Once the enemy is defeated, the immune system returns to normal and generates “memory T cells” that are ready to attack more quickly, should the same infection re-enter the body.
In most cases, that is what happens. However, in some cases of Covid-19 (exact numbers here may vary between populations), despite age, the immune system remains in a hectic state, even if the virus is no longer a threat. It continues to release cytokines, almost like a storm, which instead of doing the body any good, attacks multiple organs and leads to death. The immune system in the elderly is in a state of immune senescence, so they must remain indoors and not interact with the young, since many of the latter could be asymptomatic carriers. This is also the case for those (ageless) who have diabetes, lung or kidney disease, or are immunocompromised.
India has done extremely well so far. The challenge now is to maintain the benefits of blocking and the additional immunity that the population enjoys due to the microbial load. The next few weeks are crucial; It is not advisable to lift the lock, even temporarily.
Narinder Kumar Mehra is National President of the Indian Council for Medical Research and former Dean (Research), Indian Institute of Medical Sciences, New Delhi.
The opinions expressed are personal.