Is it advisable for other states to be following a testing algorithm like Kerala’s?
By Jayaprakash Muliyil
Kerala has been reporting doggedly higher test positivity rate for Covid-19 than most other states. Now, the test positivity rate has two factors affecting it. One is the general transmission rate, and the other is the algorithm that you use for testing. If you mainly focus on incidence of SARI, people with fever, etc—people that are symptomatic—then your positivity be slightly higher. It is advisable for a state or a city/district to have the same algorithm geographically and temporally. So, over a period of time, you can actually study the transmission dynamics.
The other issue is that, in many states, we have a large proportion who were never diagnosed, because they were either mildly symptomatic or asymptomatic or did not complete checkup. The delta variant also came around this time around, leading to an increase in the transmission dynamic. The expected herd immunity level has moved from the earlier expected level of about >50% to >70%, which means a large number had to get infected before the transmission rate starts to fall. Kerala seems to have tried to bend the infection curve, quite a lot. The net result has been that it never had overcrowding of the hospitals, and its Covid-19 mortality is the one of the lowest in the world. Ultimately, the only thing to judge the severity of the pandemic will be mortality rate.
Is it advisable for other states to be following a testing algorithm like Kerala’s? It depends on the way the latest ICMR serology report reports present itself to the states. In states where the proportion of seropositive in the total population is more than 70%, it is likely that the fall is real due to the lack of susceptible population. We should ask the question: What happened in states that showed a fall even though the cases recorded were not high? Serology will tell you the history of infections. There are two positivity rates that we talk about, one is test positivity rate and the other is seropositivity rate. Whenever there is a high seropositivity rate, the probability of another wave coming becomes extremely remote. There are some areas that have reached a seropositvity of 80%+. We have to judge action based on those areas. So, instead of over-action, we need to make sure that we manage the situation more sensibly.
So, is it effectively only about management than controlling spread, even with the possibility of the emergence of new variants, with greater immune escape? The people who have recovered are a huge number today, and this excludes people who were sub- clinically infected. We have had a small proportion getting into trouble with the Covid infection, but our whole system of healthcare is woefully lacking in its ability to deal with even that small proportion. The biggest instrument we all have, which we often overlook, is the individual’s immunity. Chances are most of us can handle the virus without any difficulty. Now, what about a mutant that completely ignores the immunity people have developed? The experience would likely be a repeat of what we went through when the virus arrived first. It’ll be almost like that—going through that whole process again, though we can make sure we don’t get infected by wearing mask, avoiding crowds, etc. But, what will happen when a new mutant comes, is anybody’s guess. It may be much weaker, and just causes infections, but isn’t strong enough to kill. The other thing is that the pattern of Covid mortality is repeated every country—you see the same thing that children are relatively safe, young adults are slightly affected, and the elderly are mostly affected. I don’t think there will be any deviation from that pattern because these diseases have their own pattern.
Some states, other than Kerala, have seen very low mortality despite a very different disease management strategy. Bihar’s reported Covid mortality, that is case-fatality, is almost as low as Kerala’s. But, reported mortality may be very different from true mortality. While, in some cases, low reported mortality could be close to a low true mortality, in many cases, there has been serious under-reporting. This may happen for various reasons—many deaths never took place in a hospital. You may have a situation where it was difficult to get to a hospital. And, it could be that even if you could reach a hospital, you opted not to. So, there is no way we can blame anybody; in the sense that how does one report such deaths accurately, those that took place at home? So, when you do a subsequent audit and look for excess mortality, then you will get a closer picture.
The author is Chairman, Scientific Advisory Committee, ICMR’s National Institute of Epidemiology