Variants, imported and homegrown, are being seen more and more, but so far they have not been epidemiologically linked to the increase.
With a steady increase in daily fresh coronavirus cases since the third week of February, with more than 89,000 cases reported on April 2, the average seven-day test positivity rate rose to 6.8% as of April 2, and with the reproduction number (R0) – how many people will each infected person infect on average: above 1.5 and steadily increasing over the last two to three weeks, the second wave has started well and truly in many states. The rate of increase of cases in India during March has been faster than at any other time during the pandemic, which is also reflected in modeling studies conducted by Indian researchers, including Gautam Menon, professor of physics and biology at the Ashoka University. Modeling suggests that the previous peak in the number of cases (about 98,000) will soon be exceeded.
While the start of the festival season since the pandemic peaked in mid-September in India, winter, the absence of movement restrictions, large gatherings, and not-so-good adherence to wearing masks and other interventions did not Pharmaceuticals did not cause any increase in cases nationwide, what is driving the current increase in cases in many states?
Reasons cited
The Health Ministry has cited general laxity among people regarding appropriate COVID-19 behavior, including wearing masks, and the lack of ground-level containment and management strategy as reasons for the increase in cases. The role of the variants, whether imported or originated in India, is not held responsible.
But Dr Giridhara Babu, epidemiologist at the Public Health Foundation of India (PHFI), Bengaluru cites three important factors: the virus, the host and the environment, which constitute the epidemiological triad of increasing cases in many states. Explaining the contribution of the three factors, Dr. Babu says in an email: “It is possible that new variants of concern are in circulation, which are probably more infectious, and some may also be an immune escape.” Host factors include antibody depletion, failure to follow proper COVID-19 behavior, and incomplete vaccination, while environmental factors include super-spreader events and poor adherence to preventive measures. The misconception that vaccination even prevents infection could also be contributing to the increase in cases.
Indian variants
“We just don’t know enough about the Indian variants to say whether they are more transmissible or more virulent, at this stage. Personally, I would think, extrapolating the very high levels of seropositivity in cities that several surveys have detected in recent months, that a more transmissible variant of immune escape is responsible, “says Dr. Menon in an email to The Hindu.
In an email to The HinduVirologist Dr. Shahid Jameel, director of the Trivedi School of Biosciences at Ashoka University, says that variants, both imported and local, are being seen more and more, but so far they have not been epidemiologically linked to the increase. “That may be the case, but there is no data to support or deny that possibility,” he says.
Explaining the delicate question of why a sudden increase was not seen between mid-September 2020 and the end of February this year despite the perfect conditions for the virus to spread in the wild, Dr. Babu says that the Population immunity threshold cannot be considered a criterion when the virus is changing or when immunity is waning. “Any infectious disease will have outbreaks as long as the reserve of susceptibles accumulates. Also, there has been the introduction of other variants due to international travel in some parts of the country, which may be more infectious than the previous strain, ”he says.
Surge in big cities
Big cities like Mumbai and Pune, which had high infection rates during the first wave, are seeing an increase. It is not clear if the cases in such cities are only in people without viruses or if reinfections constitute a significant proportion. “I am not aware of any data that is available in the public domain to address this question. Specifically, we do not know what fraction of these new cases could reflect a new, more transmissible immune escape variant that is responsible for reinfections, ”says Dr. Menon. An ICMR study covering January-October 2020 found that reinfection, probably due to older strains, accounts for about 4.5% of cases.
According to Dr. Babu, in cities that reported more than 50% seroprevalence (at least in some parts), the resurgence of cases would suggest that antibodies are rapidly declining (and are below threshold levels for generating a response ) or presence of newer variants.
In some States an imported variant (UK variant) has been identified. A double mutant variant has also been identified in at least some states, but all three experts believe that it is too early to say conclusively whether this variant is responsible for increased transmission leading to an increase in cases or a greater severity of sickness and death. This is because so far no epidemiological link has been established. That said, the UK variant and the double mutant variant are considered to be more infectious and therefore more likely to contribute to intense transmission, resulting in a faster spike wherever the variants are found. .
A systematic study is needed
One way to tell if the variant is more infectious is to perform concurrent genomic sequencing of the group of cases and establish the chain of transmission of the variants between the contacts, Dr. Babu says.
Only such a systematic study will help establish the epidemiological link of the variant. Too, in vitro tests are necessary to establish infectivity. Similarly, the degree of morbidity caused by the variant can be established by tracking the clinical parameters of individual patients. “I’m not sure if these studies are being done on a sufficient scale and the results are certainly not available in the public domain,” says Dr. Menon.
In addition, against the goal of sequencing at least 5% of the positive samples in all of India to know the appearance of new variants, only 7,664 samples have been sequenced, less than 1% of the total of positive samples from January to March 18 . “5% is an aspiration, a vision. It cannot happen overnight. Capacity, systems and logistics must be developed for this. Since INSACOG was formed, India has seen around a million cases and 11,000 sequences have been performed. So the rate is 1%. It has to go up, ”says Dr. Jameel. Dr. Menon adds: “The INSACOG group met only in January and started work in February, so there has been relatively less time to scale up.”
Conducting studies to understand the infectivity of the double mutant variant becomes even more important as non-compliance with appropriate COVID-19 behavior is uniformly deficient across India. However, the increase in cases is observed in only 19 states, and mainly in a dozen states. In the absence of timely results from such studies, which will aid policymaking, putting all the blame on people appears to be the easiest way out.
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