Why Mumbai is recording most number of cases

Mumbai reported 522 Covid-19 cases on Thursday, the highest single-day jump for any Indian city since the first coronavirus patient was detected in Kerala on January 30. Mumbai is also the Indian city worst hit by Covid-19, with 4,447 cases recorded until Friday night. Since April 13 (242 cases in 24 hours), Mumbai has consistently recorded the highest one-day increase among Indian cities, with a single exception: April 17, when it reported 12 cases. Even the exception was because of the exclusion of private lab results and not an actual dip.

Here are Mumbai’s numbers for the last 10 days — April 14: 216; April 15: 140; April 16: 177; April 17: 12; April 18: 183; April 19: 456; April 20: 308; April 21: 419; April 22: 232; April 23: 522; and April 24: 242

What explains the financial capital’s high Covid-19 numbers?

Intensive contact tracing, testing and quarantining of high-risk individuals has contributed to the consistently high numbers, according to the health department officials of Maharashtra and Mumbai. “Between 40% and 45% of our total cases are [the result of] efforts at contact tracing and fever camps in containment zones,” said Dr Daksha Shah, deputy health officer of the Brihanmumbai Municipal Corporation (BMC). According to BMC data on April 24, at least 400,000 people have been screened across 813 containment zones in the city (the number of containment zones increased to 930 on April 23, but the screening data for the new containment zones was not updated on April 24), and at the airport since the Covid-19 outbreak. Simultaneously, Maharashtra’s health department has screened 2.726 million people across the affected districts. Nearly 2 million of these are in Mumbai.

A senior BMC officer who asked not to be named said: “We have to consider the remaining 55% as well. These are coming from the untraced population, but the good thing is that many of them are coming voluntarily [for testing] and it is only later that our health officers realise that they are contacts of existing positive patients.” According to data analysis of positive patients by the Maharashtra Medical Education and Drugs Department (MEDD), 81% of the state’s patients are asymptomatic. Mumbai’s numbers are similar (80%). Notably, although the cases are rising, the mortality rate in Maharashtra is dipping.

On April 12, the city’s mortality rate was 7.41%. This reduced to 4.42% on April 24. On April 12, of the 1,996 patients detected, 148 had succumbed to the infection. Until Friday night, Maharashtra recorded 6,817 cases with 301 deaths.

Mumbai’s mortality rate has fallen too. On April 12, it was 7.09% (92 deaths and 1298 positives). This came down to 4% on April 24 (178 deaths and 4447 positives).

“Identification and quarantining of high-risk contacts has been helpful in keeping Mumbai’s numbers realistic. We will see high figures, but there is no reason to panic because these are expected results of the intensive contact tracing and isolation programme in Maharashtra,” a state government health official said. “Besides, we are aggressively testing a large number of high-risk contacts.”

As of April 23, Maharashtra had conducted 96,369 tests, of which 55,000 (or 57.07%) were in Mumbai alone, according to Praveen Pardeshi, Mumbai’s municipal commissioner. Maharashtra has recorded 89,561 negative samples. The remainder are repeat tests. On April 24, the number of tests in Maharashtra went up to 102,189, but Mumbai’s numbers were not immediately available.

According to data available with states on per million tests till April 22, Andhra Pradesh leads Indian states with 830 tests per million (41,512 total tests till that day), followed by Tamil Nadu (781 per million, 53,045 total tests) and Maharashtra (665 tests per million). Gujarat is on the fourth spot with 604 tests per million (36,829 total tests).

As of April 23, 11pm, the number of home-quarantined people in the state touched 114,398, while 8,702 were in institutional quarantine, according to data provided by the state health department. Data released by BMC on April 24 suggests that in Mumbai, a total of 98,000 people are in government-enforced quarantine — 92,000 at home (in containment zones and hot spots) and 6,000 in institutional quarantine facilities (hospital isolation wards, stadiums, sports complexes and hotels).

Pardeshi said: “A significant proportion of Mumbai’s cases are of people that have already been quarantined and those that are under observation. The ones that are testing positive, BMC had already anticipated in some measure that they may have the virus.”

“On any given day, between 70-80% of the city’s active cases are asymptomatic,” BMC deputy health officer Shah said on Thursday night, soon after the city’s highest one-day jump was announced.

Pardeshi added: “It is a good thing that so many positive patients are asymptomatic, because they don’t easily spread the disease. They don’t cough or sneeze, and transmit it to someone else. In fact, these patients are adding to our collective immunity. It is the symptomatic ones we have to pay attention to. Not only because they spread it, but because they need medical attention, we need to treat their symptoms before they aget worse and change into more complex conditions.”