The Chinese virus continues unabated in India. Despite a recovery rate of around 63%, there still exists an increase in active cases at a growth rate in excess of 3%. Further, with every passing day, every state is reporting their daily highs. The tests have increased but the high positivity rate in excess of 5% points to lot of worrying factors. There are few states which are testing relatively big but many states are hardly testing in great numbers. The conservative testing in an open economy will hardly curb the reproduction ratio. Meanwhile, the contact tracing too is experiencing difficulties generating concerns of a community transmission. While some states and doctors and medical institutions talk about the existence of community transmission, the Indian Council of Medical Research (ICMR) continues to deny so. In the contention of ICMR, rather than community transmission, India is facing local transmission in few clusters that is aggravating the mitigation of the disease. There are varying views on the testing scene in India. In contrast to other leading countries, India has hardly tested just over one percent of the population. The only country among the major or the developed ones testing less than India is Japan which has tested around half a percent but cases too are reported quite low.
One argument to probe the possibility of community transmission is the conduct of antibodies test. COVID-19 is tested through multiple means. There is the gold standard RT-PCR while there are other similar tests developed by the Indian firms. For a quick testing, the antigen tests are used. Since there is a possibility of the antigen test reporting false negatives, ICMR mandates a retest through RT-PCR. But the RT-PCR test is manually intensive which forces the authorities to go in alternative tests for quick detection. Hence any positive reported in the alternative tests, it is taken as positive while negatives are retested. Some diagnostic labs have developed antibodies test also.
The antibodies tests are not for diagnostics. When an external agent like the bacteria or the virus invades the body, the body develops the antibodies to fight against them. In fact, the greatest weapon against any disease is the body’s own resistance and development of antibodies. These antibodies once developed will remain in the body for a pretty long time. Even when they fade out, the body’s immune system retains the memory of the same and thus when the same virus or any other microbe strikes the body, the body is quick to produce the antibodies to counter against the same. In any battle, it is the race between the microbes and the antibodies to produce faster than the other. If the antibodies are produced fast, their rate of growth increase than the growth of microbes thus resulting the body’s victory over the viral, bacterial or protozoan microbes.
In the normal course, the antibodies take some time to produce. There are IgM which are produced within a week or so of the infection and these are the temporary ones designed to fight the infection. Over a period of time maybe after 14 days or so, IgG antibodies are produced which are long lasting. The antibody tests designed and developed to test for the Chinese virus antibodies are more geared for the latter or IgG antibodies. There are no reliable tests having high sensitivity and specificity to detect IgM antibodies. IgG are usually developed once the active phase of infection is over. Detection of these indicate the body has contracted the infection at least a couple of weeks before. Detection of IgM detects the current infection.
Recently a few surveys have emerged reporting on the prevalence of the IgG antibodies in Delhi and other parts of the country. A private firm having conducted around 60000 tests in different parts of the country reports prevalence in the range of around 50% in some blocks to less than 10% in some other blocks. Some leaked surveys purportedly from ICMR in Kolkata etc report around 15% or so in containment zones. In Delhi, there has been release of an official survey which talks about the possibility of around 23% infection in Delhi. Implied is through the sample survey conducted slight less than one in four in the national capital have had some exposure to the Chinese virus sometime in the recent past. Since the survey concluded on July 10, the percentage refers to dates around June third week or so. In the current context, the infection might have expanded to around 30% of the population. This also implies the fatality rate falling well below half a percent. Yet there are certain riders to the survey.
While the surveys are based on a sample size, it certainly does not point to the specific persons exposed to the virus. If nearly one in four are exposed in Delhi, it is important to find out who are those people. These are quite useful in extracting plasma for treatment of the current patients. Plasma treatment at early stage might be very useful, but currently shortage of donors is hindering the same reducing its efficacy. The similar would be the state of many other cities. In the battle against the pandemic from Wuhan, it is important to map each individual no matter the sheer volume of population is around 140 crores in India. It is its infectiousness and the consequent possibilities of the mortality that is the cause of concern and panic. Lockdowns are essentially being used to prevent these. If there is sufficient evidence of people having contracted antibodies to the extent that the surveys are claiming, then there would less concern.
Therefore, as one decodes the results, it throws up the pointers. There are millions of coronavirus and India or perhaps people in South or South East Asia might have had exposure to them in the past thus creating these antibodies through the development of cross-immunity. Therefore the efficacy of cross immunity is tested and validated through antibodies tests perhaps. Secondly, it should not stop at surveys but used as a complement to the entire diagnostics and preventive care strategy. There must be antibodies test on demand. Let any individual go and test himself or herself at any of the authorised labs. These will indicate the possibility of antibodies present either through immunity or cross immunity.
The antibodies test will indicate past infection. If there is existence, it proves an exposure. Testing their contacts for antibodies will help in identifying the spread patterns and perhaps give an indication on who develops symptoms and who does not. In fact, as the fears of community transmission increase, the only way to trace the roots of the infection, it has to be the antibodies test across the length and breadth of the country. It is time that the authorities integrate it in the contact tracing strategy rather than being confirmative survey.
Thoughts on Theory and Practice 