Paschim Burdwan(Fig. 1) is a densely populated area with 2,882,031 people in it . The district is identified as the major industrial hub in eastern India . To the best of our knowledge, this is the first such study concerning patient demographics and pollution change in this area of the country.
From the study period, it is reported that the Covid 19 cases gradually increased in this area to 1537 during August and the number reached 3965 in September 2020. The curve flattened in January, February, and March 2021.This concluded thatthe surge of the first wave was in September 2020 declined in December 2020 It is important to note that during this time (30th December 2020)Kolkata reported the First Bengal strain emerged (variant VUI-202012/01 or B.1.1.7) which has 17 mutations, [13, 14].After that, there was a sudden rise of positive casesin April 16743, which heralded the second wave in the month of April 2021. The month of May experienced the maximum number of cases of 21132, which can be attributed to the heavy public gatherings before elections which were held on 26th April 2021 in the district.In June 2021 the cases dropped and further declined in July 2021.which supports the studyby Sharma N et al, which also shows the exponential growth of positivity from April 2021 onwards .Mainly the double mutant 'Delta' strain (B.1.617) and the triple mutant 'Bengal Strain' (B.1.618) were responsible for the increase of positive cases during the 2nd wave [15, 16].The ‘Delta’ strain along with the triple mutant ‘Bengal strain’ show higher transmissibility
The number of deaths also increased along with the infectivity in the second wave (Fig. 2). This may be attributed to the explosive nature of the second wave led to a large number of people being affected in a short span.This may have put the health infrastructure under pressure, making hospitalization possible for only more severe patients, which may have resulted in higher mortality among the hospitalized patients .
In the ≤ 19 age group for the first wave, the positivity rate was (5.38% ) which increased to (5.85% ) for the second wave.A similar finding is reported by Kumar et al which showed higher positivityin < 20 individuals bythe second wave . The lower Covid-19 cases in the age group ≤ 19among all other age groups was probably due to better immunity of the younger generation. Affected children were also considered the potential indicator for the second wave, as they are likely to have heavy nasal loads and would be silent spreaders of the disease especially during the sequential opening of the schools. The maximum affected age group for both the waves was the ≥ 20 to ≤ 45 years age group. The higher rate of infection in this group is probably due to the presence of more working people, compared with the first group, who had higher environmental exposure .A similar result is also reported in the literature which indicated a higher proportion of patients found in the age group of 20–39 years .
People of the age groups of ≥ 45 to ≤ 60 and above were found to be slightly more affected in the second wave. Supporting our result many previous studies showed that elderly people were more susceptible to Covid-19 and the pathogenic severity which is also higher for those who had co-morbidities like hypertension, diabetes, structural lung diseases, etc. [18, 20, 14]. As the age increases the innate immune responses decreases, and a shift in T-cell subpopulations leads to a decrease in naïve T-cells and an increase in memory T-cells, which reduces the response against novel infectious agents . But, interestingly the number of cases decreased in the second wave for (≥ 60 years) age group and may be dueto the government's initial vaccination drive which began from 1st March 2021 for senior citizens and above 45 years. Senior citizens were first vaccinated according to the government’s guidelines .
In the age-group-wise comparison between genders in terms of % positivity (2020 and 2021), (Males: 63.12% and Females: 36.87%) it was found that the males were more affected in all the age groups except for the ≤ 19 age group in which males were 4.74%positive but percentage increased to 7.44% in case of females. Sex hormones are very crucial for the development and activity of the immune system against viral infections . This may have contributed to the sexual dimorphism observed in immunological responses to the virus. ACE2 expression and activity are higher in males than females which may have resulted in the differences in COVID-19 infection and fatality in males and females. ACE2 activity is found to be higher in males than in females as reported in some studies [22, 23]. Though, it may be true that females acquire lesser severity in females than males . As they possess higher cell-mediated and humoral immune responses .The result may be explained by a study done by Pinchoff J et al in Uttar Pradesh and Bihar which reveals that women were less likely to practice COVID guidelines as they are unable to identify the main Covid-19 symptoms correctly, due to challenges in accessing information or receiving less accurate information of Covid-19 symptoms.
It is seen from Fig. 4 that the cases and deaths of TB reduced from 2019 to 2021. Apparently, the increased use of masks and frequent lockdowns were the reasons for this reduction in thenumber of cases and deaths of TB. But this may not be true as a reportreleased on 12 May 2020 by WHO suggested that the COVID-19 pandemic led to a global reduction of 25% in expected TB detection for 3 months. In support of this report, other studies showed that the cases were undetectedas the number of testings was hampered during the covid months [26, 27]
Anotherconcern would be that Covid-19 has "TB-like" symptoms and covid-19 carries a stigma in many communities and this stigma may transfer to individuals with TB as well.As the p-value is less than 0.05, cases and deaths are not the same across the years at a 95% level of significance.
The area remains heavily polluted throughout the year. The investigation was aimed at examining whether the pollution got controlled during the lockdown months for various parameters NOx, COx, and SO2 as well as PM2.5 and PM 10 and it was seen from the table that there was no reasonable variation in these parameters during the study period of July of 2019, 2020 and 2021. Though it was expected that the values of these parameters would drop due to lockdown. The reason for no appreciable change in these values may be because the industries were in operation during the lockdown phase also. The assumption that pollution may cause a rise in the number of cases among age groups was not found correct. Pollutionwas not found to have any impact on the increasingCovid cases and deaths during the study period of the mentioned district.