The TLDR: On Sunday, we recorded 52,972 cases—adding the highest number of daily cases in the world. Other estimates put that number at 53,641. Either way, the grim achievement remains the same: We have sped past both the US (47,511) and Brazil (25,800). But that number is likely still an underestimation. The reasons: decline in testing and faulty tests. Here’s a quick guide on how to read these numbers.

First, the bad numbers

• India became #1 in the world on Sunday in the number of cases added in 24 hours.
• But we are still behind both the US and Brazil in our overall total, which stands at 1,855,745 as of Tuesday. 
• Now, our numbers dipped to 49,134 on Monday—but that slight post-weekend decline has been a consistent trend for over three months. It likely reflects lower testing numbers on Sundays. 
• Otherwise, we’ve consistently added 50K-plus cases every day for a week.

The hotspots: Delhi is showing clear signs of recovery—with a continuous decline in the number of active cases for nearly a month. Tamil Nadu and Maharashtra appear to be stabilising. Maharashtra’s number of recoveries is on the rise, and exceeds the number of new cases. Tamil Nadu is following a similar trend.

So why are the numbers still rising? Because the number of active cases in other states—Andhra Pradesh, Karnataka, Bihar, Kerala, West Bengal, Uttar Pradesh—have been rising rapidly in the last month. Also rising: Gujarat, Madhya Pradesh and Rajasthan.

Numbers are bad, but are they accurate?

Maybe not. Our totals may be worse than the official tally. The reasons include:

Decline in testing: The number of daily tests has been falling over the past few days—dropping sharply from 640,000 on Thursday to 381,000 on Sunday. We are now testing only 14,640 persons per million. The less we test, the less we know. 

More importantly: The higher case numbers—accompanied by lower testing—means that our positivity rate is climbing. In other words, a greater percentage of the tests are coming up positive. Our positivity rate hit an alarming 13.9% on Monday.

Faulty tests: Much of India’s ramp up in testing relies on rapid antigen tests (RAT). These tests detect viral proteins in the body. The true gold standard for Covid testing is the Real-Time-Polymerase Chain Reaction (RT-PCR) tests which detect the actual virus. RATs, however, are quicker, easier to perform and cheaper. But they also pose a big problem:

• At the beginning of July, RATs were only 4-8% of all tests performed. As of today, they account for 45% of that total. 
• The problem: They have a high ‘false negative’ rate of 40-50%, i.e. people who have Covid test negative—and that failure rate is worldwide. 
• In India, that percentage is even worse in places like Mumbai. Data gathered from two major city labs showed that 65% of symptomatic patients who tested negative in antigen tests were later confirmed as positive in RT-PCR testing.

Delays in testing: Our labs have long struggled with a huge backlog of tests—which in turn creates further delays in reporting our numbers (as we explained here). And the rising numbers haven’t helped the cause. Backlogs in turn skew the data, and make it hard to detect clusters in time. 

Point to note: A recent Lancet study found that a two-day delay in testing results in 50% more transmission of the virus. In Hyderabad, test results can take up to five days. As of July 22, some of Tamil Nadu’s worst-hit districts had a backlog of 8,000-plus samples—and experienced a seven-day delay. In parts of Kerala, the average daily number of pending test results is 5,500.

The bottomline: The actual number of cases far outstrips the official total—which is already very high. Two serological surveys in Mumbai and Delhi tested residents for antibodies—to see how many have been infected. The percentage in Delhi: 23%. The percentage in Mumbai: 57%. Also: 20% of those who volunteered for a vaccine trial in Delhi already had antibodies. The upside: they also show that a great number of Indians are not falling seriously ill. And the total number of recoveries—1,230,509—is inarguably a good thing. But effective and immediate testing remains a challenge. And without it, we cannot hope to bend this ever-steepening curve.

Reading list

The Print has a great set of charts that show testing and positivity rates. Times of India looks at the performance of antigen tests in India. Firstpost has a guide to the different kinds of Covid tests. Science magazine explains how antigen tests work, and why they often fail. Also read: Bloomberg News reports on the lack of good data on death rates—which is a far more serious problem.