India: two-thirds of population has been exposed to SARS-CoV2


Cases of COVID-19 are surging around the world, but the course of the pandemic varies widely country to country.

To provide you with a global view as we approach a year and a half since the official declaration of the pandemic, The Conversation’s editors from around the world commissioned articles looking at specific countries and where they are now in combating the pandemic.

Here, Rajib Dasgupta from the Centre of Social Medicine and Community Health at Jawaharlal Nehru University in New Delhi writes about India following its devastating wave of infections earlier in 2021. You can see the whole collection of articles here.

What explains the rapid spike and then sharp decline of cases of the April-to-June wave?

India emerged in June and July of 2021 from a particularly savage second wave of COVID-19, with total confirmed cases at about 32 million and more than 400,000 deaths. But this could be a dramatic under-counting. Alternative estimates have put excess deaths in the range of 3.4 million to 4.9 million.

This wave was driven by multiple coronavirus variants, including alpha, which was first detected in the U.K., and delta, first identified in India and now the main source of infections in many countries. Because the emerging threat was not recognized early enoughhealth care services were overwhelmed starting in early April, with the lack of reliable oxygen supply becoming a major problem.

Both the alpha and delta variants are highly contagious, with delta being nearly twice as transmissible as the original strain of SARS-CoV-2.

The rapid rise in cases in India is attributed to the high viral load – the amount of virus infecting a person – of delta, which is about 1,000 times higher than other strains.

This resulted in widespread infections among household members with rates as as high as 80% to 100%.

The decline of cases in India has been surprisingly rapid given that there were daily new cases in the range of 400,000 in the first week of May and the test positivity rate in some districts was as high as 20%.

Similar sharp declines were observed more recently in the U.K., Netherlands and Israel – perhaps a result of a combination of high vaccination rates and high infection levels. Daily cases in India are now between 30,000 and 40,000 per day.

What’s the progress with vaccination?

With the vaccination campaign substantially picking up in India, about 15% of adults have now received both doses of the vaccine and nearly 40% a single dose. A record 8.8 million doses were administered on Aug. 17, 2021 in a bid to achieve the 250 million target for August, although some projections consider it likely will be missed.

Supply situations continue to be challenging. Production of the Covaxin vaccine, developed by Indian company Bharat Biotech, did not accelerate as envisaged, at least in part due to quality issues of some batches. Negotiations with Moderna haven’t worked out and Johnson & Johnson received emergency authorization for use in August.

Production of the Russia-developed Sputnik V by an Indian partner has been delayed and manufacturing is expected to be on track only by September. Covishield from AstraZeneca continues to be the workhorse, accounting for 87.5% of the vaccines administered to date.

An estimated 9 million doses will need to be administered daily through the next five months to meet the target of vaccinating all adults by Dec. 31, 2021. For comparison, average daily vaccinations in the U.S. at its peak in April was 3.5 million per day. An added challenge for the Indian campaign will be the vaccination of children.

Vaccination of an estimated 400 million in the 2-18 years age group is likely to begin in March 2022 though emergency authorization is expected to begin this month.

How many of India’s 1.3 billion people have been infected?

In the aftermath of the second wave from roughly April to June, the Indian Council of Medical Research conducted the fourth round of a national sero-survey in June and July 2021 to test for antibodies in blood samples from residents across 70 districts of 21 states.

The overall sero-prevalence was 67.6%, a huge increase from 24.1% recorded in the third round from December, 2020 to January, 2021. The presence of antibodies indicates that a person has either been exposed to the coronavirus or has been vaccinated.

Sero-positivity among children was 57.2% in those aged 6-9 years and 61.6% among those who are 10–17 years old. Experts believe that there is not much scientific evidence that children would be disproportionately vulnerable in a third wave.

The government, however, anticipates the possibility of intermittent surges in the number of cases and prepared operational guidelines for children and adolescents in preparation for a third wave. Seroprevalence among those above 45 years was 77.6% and 66.7% among younger adults, indicating the effect of vaccination as well as infections.

The coronavirus had spread through the entire country; seroprevalence among the rural population (66.5%) was only slightly lower than in urban counterparts. A wide range of interstate differences have emerged, from a low of 44.4% in Kerala to 79% in Madhya Pradesh.

The extent of undercount – the difference between estimated cases (based on seroprevalence) and actual cases detected by RT-PCR and rapid antigen tests – is particularly worrying. Nationally, the system missed 33 cases for every one detected.

What are the prospects for the weeks and months ahead?

With about 40,000 cases and 400 deaths each day as of mid August, a new uptick is likely in the cards. The Indian states experiencing most of these new cases are those with relatively lower sero-prevalence, ranging between 50% and 70%. The 400 million sero-negative pool – that is people who have not been infected or had the vaccine – continues to be a large vulnerable group.

Forecasting by modelers indicates a third wave beginning in August and peaking at 100,000 to 150,000 infections a day by October. An alternative projection expects the peak in cases going until November. States currently reporting higher daily cases are also testing at two-three times the national average.

The case fatality rate in these states is also lower than the national average and health service capacities are not yet stretched. For its part, the federal government announced the second phase of its emergency response policy with targets that go until March 2022.

Has the economy opened back up?

COVID-19 vaccination in India has been marked by both inequity and hesitancy; negotiating both will be crucial in the weeks ahead.

The range of vulnerabilities have included rural and remote locations and a lack of access to the internet; a gender divide has emerged too with more men being vaccinated than women. As vaccination progresses with underlying inequities, the phenomenon of “patchwork vaccination” emerges – pockets that are highly vaccinated and adjacent to places or communities with low coverage. The communities with low coverage are vulnerable to hyperlocal outbreaks.

Most economic activities have resumed, and the education and entertainment sectors are opening up too. A joint statement on June 6, 2021, issued by the public health associations in India urged that district-level sero-surveys be undertaken by the state or federal health services to enable a more granular understanding of the epidemiologic context to enable planning. While this was accepted in principle, such systematic surveys have yet to be rolled out.

The World Health Organization advises that public health and social measures in the context of COVID-19 be guided by local transmission dynamics. Planning at the district level in India shall be crucial in the journey ahead.

COVID-19 pandemic has been impacting the life and economy across the globe since December 2019 and has caused major disruptions (Walker et al. 2020). The COVID-19 pandemic has resurfaced in India in the form of a hard-hitting second wave. The COVID-19 has brought a threatening challenge to Indian society and the economy (Sarkar and Chouhan, 2021).

India’s devastating second wave of COVID-19 has overwhelmed its health system and the country (Ranjan, 2020, Ghosh et al., 2020). The second wave of COVID-19, caused by severe acute respiratory syndrome (SARS-CoV-2), has struck India severely, with a significant case fatality rate (Tomar and Gupta, 2020).

The situation in India is more critical as it has a huge population, poor medical infrastructure and complex socio-economic structure, where self-isolation, social distancing and quality treatment are the key controlling factors to neutralise the impact of the disease (Kaliya-Perumal et al., 2020, Bhuyan, 2021). The growth of towns and the consequent need for more supplies have damaged the delicate environment of India, where there are high levels of smog, fine dust, and water pollution.

Sulfur dioxide (SO2), Nitrogen dioxide (NO2), and particulate matter (PM) contribute in part to the toxins causing environmental contamination (Sarkar and Chouhan, 2020, Huang and Brown, 2021, Bherwani et al., 2021). Many Indian urban communities, including Mumbai, Kolkata, and Pune, are at the risk of air contamination (Conibear et al., 2018).One out of eight (about 12.5%) deaths in 2017 in the country were attributable to high rates of respiratory disease, stroke, heart disease, diabetes, and lung cancer, all conditions for which a certain percentage of cases result from severe air pollution (Gurjar et al., 2016).

Some relevant scientific literature highlights that exposure to air pollution may be relevant to virus infection spread, and more recent literature focuses on COVID-19 diffusion (Cheng et al., 2020, Report et al., 2020, Saha and Chouhan, 2021). On January 30 2020, the Director-General WHO declared that the outbreak of novel coronavirus (2019-nCoV) constitutes a Public Health Emergency of International Concern (PHEIC) as per the advice of the International Health Regulations (IHR) Emergency Committee (Black et al., 2020).

In the first surge in 2020, COVID-19 has infected nearly 20 million people across the globe, with 90 countries in the community transmission stage (Bherwani et al., 2021). The daily reported confirmed cases started to rise from February 2021 in India (Sengupta et al., 2021). The mid of April 2021, registered sudden hike over thousands of daily death was observed around the country (Khanna, 2020).

Multiple factors are involved in driving the second wave of COVID-19 in India, such as the complex interplay of mutant strains, violation of COVID appropriate behaviour, and government and public complacency on initiation of the vaccination drive (Kar et al., 2021). The situation turned into a bleak one when the country witnessed the daily deaths of over three thousand at the end of April 2021. On April 26, 2021, India saw the highest daily tally of new SARS-CoV-2 infections ever recorded globally, 360 960, taking its pandemic total to 16 million cases, second only to the USA with more than 200000 deaths (Thiagarajan, 2021).

As of May 18, India had reported more than 26.4 million confirmeded cases and over 274000 deaths from COVID-19 (Balsari et al., 2021). 29.27 million cases have been reported in India during the pandemic, with a case fatality rate of 1.24% (363,079 deaths) up to June 11, 2021 (Kar et al., 2021). At the beginning of the second wave, the country’s Case Fatality Ratio (CFR) has hovered around 1.35% to 1.40%.

At the onset of the COVID-19 pandemic, India imposed the world’s strictest nationwide lockdown beginning from March 25, 2020 (The Lancet, 2021). But, the situation during the onset of the second wave was aweary in the whole country. WHO confirmed 15,510 new cases in India on March 1, 2021, and the peak had been formed with 414188 confirmed cases on May 7 (Saha and Chouhan, 2021).

The curve of new cases indicated a sharp rise from April onwards in India. Surprisingly, the present peak pandemic situation addresses a difference of 3,14,692 new confirmed cases than the previous peak (September 18, 2020) (Nishiura, 2010). It indicates the severity of the second outbreak in India. On April 17, 2021, the country peaked, considering confirmed cases that accounted for 10.6% of the country’s total population. On May 11, 2021, the WHO reported about 16,411 confirmed cases and 178 deaths per million (COVID-19 : STATUS ACROSS STATES 2021).

On the same day, the country’s CFR was 1.09%. The spread of the infection is more belligerent in the states of North-East India. From the beginning of the second wave, the outbreak was centred around the megacities of India, especially in NCT of Delhi, Mumbai and Bengaluru urban (The Lancet, 2021). On January 4, 2021, a total of 7.57% people of the country were infected by the coronavirus (Adviser et al., 2021). But, by May 11, the figure reached up to 16.67% (Thakur et al., 2012).

At this stage, the main challenge is to organise the basic life saving treatment facilities at the grass-root level and especially assure the supply of oxygen and vaccines (Ioannidis, 2021). In addition to this, the legislative assembly election in Assam, West Bengal, Tamil Nadu and Kerala with mass political gatherings and rallies has made the situation out of control. India is the largest democratic country globally; however, looking at the current COVID-19 situation, the state elections (Assam, Puducherry, Kerala, Tamil Nadu, and West Bengal) could have been postponed till normality (Samarasekera, 2021). Many states did not go for the full lockdown this time and relied on night curfew to keep the local economy alive. As well the largest vaccine drive in the world was started in India in 1st week of April.

At the same time, 6.06% of the total population was vaccinated (1st and 2nd). On May 11, roughly 13.3% people have got vaccinated (COVID-19 : STATUS ACROSS STATES 2021). The increase is not so promising for such a country with a billion-plus population. The changing nature of the virus and countrywide high oxygen demand worsened (Timilsina et al., 2020). A rapid increase in the daily incidence of serious cases creates a shortage of medical instruments, oxygen, hospital beds and lifesaving drugs (Gupta et al., 2021).

In a knee jerk reaction, the central government and its expert team started constructing the badly needed medical facilities to overcome the shortages. However, this frenetic activity of augmenting facilities comes in the middle of an ongoing and exponential rise in cases. In contrast, it should have started way ahead of these doldrums, say experts (Black et al., 2020).

The country’s average CFR falls significantly down from 1.45 % (in January 2021) to 1.09% (in the first week of May) (Grech and Cuschieri, 2020). Considering the second outbreak, the study incorporates a new angle to find out the district wise spatial pattern of the concentration of COVID-19 confirmeded cases and Case Fatality Ratio (CFR) in India (Dhillon et al., 2020).

The paper aims to know the spatial clustering pattern of both the concentration of confirmed cases and CFR. Spatial Cluster analysis (SCA) has two general purposes. The first is data preprocessing, where clustering is used as an automated, unsupervised step for organising data, increasing the efficiency of search or query algorithms, and improving the system’s overall performance.

The second is exploratory, where clustering is used for knowledge discovery and for motivating new hypotheses based on discovered patterns (Sengupta et al., 2021). In this study, the SCA technique well presented the pattern of spread of the infection in the second wave.

The work will surely help the policymakers of the country-firstly to understand the spread of the second wave from the concentration of positive cases and its spatial clustering, secondly to identify the hot-spots of the concentration and thirdly to implement COVID-19 pandemic combat strategies like demarcation of containment zones, lockdown strategies, vaccine drive with paramount importance, blocking intra-state movements and most importantly thorough preparation at the medical level (district, block and village level).

This study incorporates a completely new angle to reveal the hidden geospatial pattern of the second wave at the district level with spatial statistics.


In this study, the concentration of confirmed cases comprising the asymptomatic patients reveals the pattern of statistically significant clustering around the two megacities of India i.e. NCT of and Mumbai. Surprisingly, in eastern Kashmir and Leh-Ladakh, the LQ revealed statistically significant HH cluster in March. But, in May, it becomes a non-significant cluster. In Eastern India comprising the districts of Ganga and Brahmaputra valley in Bihar, West Bengal and Assam, Nagaland, Manipur and Meghalaya have a relatively low concentration of LQ.

In South India, whole Kerala and districts of Karnataka surrounding Bengaluru urban show the severity of the concentration of confirmed cases. The NCT of Delhi and Mumbai remain the main hot spot of concentration till May. In this peak, the confirmed cases gradually spreads over the whole Maharashtra and the neighbouring state of Chhattisgarh starts affected rapidly. The CFR indicates wide dissimilarity in comparison to the LQ index in LISA maps.

In March, the very high concentration of confirmed cases in Kerala and districts surrounding Bengaluru urban did not report high CFR. The CFR cluster bridged up the districts of Maharashtra with some distrcts of middle-North India and shows a continuous directional progression (N-E). CFR is insignificant in the districts of eastern Kashmir and Leh-Ladakh. The LQ and CFR pattern matches by chance only in case of Eastern India (LL category). I

n May, the HH clusters of CFR clearly indicates two pivots of the infection i.e. Mumbai urban-Pune-Nasik-Kolhapur region (comprising Goa) and NCT of Delhi (comprising Punjab & Haryana). The districts of the far west (Rajasthan & Gujrat), middle India (Madhyapradesh, Chhattisgarh, Bihar & Uttar Pradesh), West Bengal, Sikkim and Tamil Nadu do not show any significant trend of clustering of CFR in this peak time of Covid-19 pandemic. This analysis decodes the spatial pattern of the concentration and spread of the infection from March to May (second wave). Finally, the pattern would give us some idea how to combat with the present situation and to get prepared for the predicted third wave.

Fig 1
Fig. 1
District-wise spatial variation and clustered pattern of confirmed cases; a) LQ of confirmed cases (01-03-2021), b) LQ of confirmed cases (10-05-2021), c) spatial cluster of the concentration of confirmed cases (01-03-2021) and d) spatial cluster of the concentration of confirmed cases (10-05-2021).

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