Abstract
By February 2021, the overall impact of the COVID-19 pandemic in India had been relatively mild in terms of total reported cases and deaths. Surprisingly, the second wave in early April becomes devastating and attracts worldwide attention. Multiple factors (e.g., Delta variants with increased transmissibility) could have driven the rapid growth of the epidemic in India and led to a large number of deaths within a short period. We aim to reconstruct the transmission rate, estimate the infection fatality rate and forecast the epidemic size. We download the reported COVID-19 mortality data in India and formulate a simple mathematical model with a flexible transmission rate. We use iterated filtering to fit our model to deaths data. We forecast the infection attack rate in a month ahead. Our model simulation matched the reported deaths well and is reasonably close to the results of the serological study. We forecast that the infection attack rate (IAR) could have reached 43% by July 24, 2021, under the current trend. Our estimated infection fatality rate is about 0.07%. Under the current trend, the IAR will likely reach a level of 43% by July 24, 2021. Our estimated infection fatality rate appears unusually low, which could be due to a low case to infection ratio reported in previous study. Our approach is readily applicable in other countries and with other types of data (e.g., excess deaths).
Highlights
The COVID-19 pandemic has lasted for more than a year
While the pandemic started to slow down in most developed countries due to the combined effects of high infection attack rate and high vaccination coverage, the impact in India had been mild in terms of the total number of deaths and cases, until April 2021
We proposed a simple model approach for modeling and forecast the COVID-19 epidemic in India
Summary
The COVID-19 pandemic has lasted for more than a year now. The severity of the impact of COVID-19 varied wildly across nations. An on-going second wave of the COVID-19 devastates India ‘unexpectedly’ since early April 2021. On March 12, 2020, the first COVID-19 fatality in India was reported [2]. By early July 2020(3), the seroprevalence reached 57% or 16% among inhabitants in three slums or other areas of Mumbai, which is the commercial capital of India. These high infection attack rate (IAR, proportion of population got infected) caught wide media attention. A new variant, named Lineage B.1.617, was detected in India in October 2020 [5, 6] and is blamed as one of the factors for the second wave. From the global initiative on sharing all influenza database [8], B.1.617 contributed to 63.6% infections of COVID-19 in India in April 2021
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