The Brihanmumbai Municipal Corporation (BMC) started releasing a detailed daily PDF filled with information on a variety of indicators such as mortality, containment zones, bed capacity, vaccinations, etc. from June 2020. As can be imagined, such data is extremely useful not only for formulating short-term policy measures but also for assisting longer-term academic research. A long-standing issue with using the data, however, has been that the authorities follow a process of replacing the PDF each day with fresh information and removing the prior day's document. This practice has limited any kind of temporal analysis till now.
At IDFC Institute, we have been able to gather all such PDFs from July 2020 until the present. We are in the process of converting all relevant indicators to a machine-readable output and will put them out as a public-facing database in due course. In the meantime, we will put out a brief analysis of them along with the related datasets.
In our first post, we discussed COVID-19 mortality data for Mumbai (read here). This week, we have compiled and analysed COVID-19 testing data over time and looked at the following variables
Total positive tests
Total number of tests conducted (including the share of RT-PCR and antigen tests)
Analysis of Testing Data and Policy Changes over time
Setting up an effective and sustainable testing strategy for a communicable disease like COVID-19 is critical. It helps to monitor transmission trends and treat, isolate or hospitalise infected people. It not only supports the overall public health response to the pandemic but also helps mitigate its impact on vulnerable populations and strained healthcare systems. Widespread testing and effective contact tracing should be the key components of the pandemic response strategy. It can help to suppress the resurgence of local outbreaks by tracking new cases and in gaining knowledge on the evolution of the pandemic.
The highest number of tests conducted in Mumbai on a single day is 56,226. The total number of tests conducted till 7 May 2021 is 54,79,900 - of which 62% were RT-PCR tests and the remaining 38% were rapid antigen tests. Before the second wave, RT-PCR tests composed 79% of the total tests (as of 28 Feb 2021). The ratio changed without a decrease in the number of RT- PCR tests.
The following changes have been made over the past year to ensure that we have an effective and comprehensive COVID-19 testing strategy:
No medical prescription is required for testing any individual for COVID-19.
Laboratories are supposed to give a preference to high-risk and symptomatic patients who require hospitalisation.
Pregnant women are given preference for testing.
All laboratories have been instructed to upload test results on the ICMR platform within 24 hours to support contact tracing.
Laboratories started conducting RT-PCR tests in May 2020 whereas antigen tests were introduced in July 2020.
During the second wave, the BMC significantly increased the number of rapid antigen tests conducted through the organisation of testing camps at train stations, malls and other at risk or highly affected areas.
Test Positivity Rate Analysis
The Test Positivity Rate (TPR) indicates the proportion of total tests conducted that turn out positive, indicating the presence of the virus. It helps public health authorities assess the current level of COVID-19 transmission in the community and understand if enough testing is conducted considering the number of people who are getting infected. A high test positivity rate generally suggests that there is a high level of transmission and/or that testing needs to be ramped up.
The highest TPR recorded in Mumbai is 54% on 22 May 2020. Despite an unprecedented increase in cases during the second wave, the highest test positivity rate recorded during this period is 27% on 4 Apr 2021. This indicates that the authorities in Mumbai have managed to ramp up testing due to which the TPR stayed much lower during the second wave. The number of tests conducted during the second wave has increased by approximately three to four times compared to the first wave in Mumbai.
The Government of Maharashtra has used the TPR as an important indicator to guide the post lockdown reopening strategy. Relaxations were announced for districts with a TPR rate equal to or less than 10%. Mumbai’s TPR has been below 10% since 3 May 2021.
Both RT-PCR and antigen tests are used to diagnose active COVID-19 infection. RT-PCR tests are more accurate but are processed in a lab and results are available within hours or days. Antigen tests used by the BMC are mainly rapid tests that can provide results within a few minutes and be used in community settings.
Reading the graph: On 8 Apr 2021, 55,471 tests were conducted in total (this includes both RT-PCR and antigen tests). On that day, 8,174 tests were positive hence a TPR of 15%.
Analysis of Trends in COVID-19 Cases during the First and Second Waves - Mumbai V/S India
During the first wave of the pandemic, 2,650 cases were recorded on 7 Oct 2020 in Mumbai. This was the peak of the first wave. It took approximately 15 days for Mumbai to halve the number of cases from the peak. The second wave showed a similar pattern. Mumbai recorded 10,033 cases on 7 Apr 2021. The number of cases reduced by almost 50% on 25 Apr 2021. Thus, it took Mumbai almost the same time i.e., two weeks to reduce its caseload during both waves.
This pattern is not similar for India. On 16 Sep 2020, India recorded 97,894 cases. This was the peak of the first wave. This number was reduced by half in approximately 40 days i.e., by 26 Oct 2020. Thus, during the first wave, it took approximately six weeks to reduce the cases by 50% from the peak. During the second wave, the peak of cases (4,14,188 cases) was recorded on 16 May 2021. This number was down to 50% by 25 May 2021. Thus, India recorded a 50% decrease in daily COVID-19 cases in just three weeks from the peak of the second wave.
Click here to view or download the data. All data provided as-is from BMC’s COVID-19 response War Room Dashboard and may contain errors or be incomplete.
Disclaimer: All visualizations are based on the testing totals available in the report as of 7 May 2021.