The coronavirus took hold slowly in India, but six months after its first confirmed infection it has overtaken Russia to record the world’s third largest caseload.
With the world’s second-largest population, much of which lives packed into cities, the country was perhaps always destined to become a global hotspot.
But the data behind its case numbers is questionable, because India is not testing enough, and an unusually low death rate has baffled scientists.
Here’s five things we know about the spread of coronavirus in India.
1. India’s cases are rising fast
India has seen a series of record spikes recently, adding tens of thousands of cases daily. It recorded most of its confirmed cases in June, within weeks of reopening after a rigid lockdown.
As of 8 July, India had 742,417 confirmed cases.
But the true scale of infection rates in the population is unclear, according to virologist Shahid Jameel.
The government conducted a random sample of 26,000 Indians in May, which showed that 0.73% had the virus. Some experts have reservations about the sample size, but others, such as Dr Jameel, say it’s the only country-wide indicator they have to work with.
“If we extrapolate that to the whole population, we would have had 10 million infections in mid-May,” Dr Jameel said.
Given that confirmed cases in India have been doubling every 20 days, that would put the current total between 30 and 40 million.
The gap between confirmed cases and actual infections exists in every country, but to different degrees. Testing is the only way to bridge it. “If you test more, you will find more,” Dr Jameel said.
That’s what has happened in India in recent weeks – as the government ramped up testing, case numbers suddenly increased.
India has done more than 10 million tests since 13 March, but more than half of those happened after 1 June.
2. India is just not testing enough
India’s official caseload is high in absolute numbers, but it’s relatively low in per capita terms. The world, on average, has three times as many cases as India per capita – a fact pointed out by the government recently.
But, according to Dr Jameel, India’s per capita caseload is low simply because it tests so little.
Compare India to countries that have a high per capita caseload and you will find those countries are testing far more.
India’s caseload is nearly invisible on this scale because its testing rate is so low.
But it’s not just about how much you test, it’s also about who you test.
India’s emphasis on test and trace early on limited the pool of people it was testing to high-risk cases and their contacts – and kept it from expanding to the wider population.
Test and trace is insufficient once the infection starts to spread rapidly, said Himanshu Tyagi and Aditya Gopalan, mathematicians who have studied Covid-19 testing strategies. It helps with containment, but it does not discover new cases that have emerged undetected in the community, Mr Tyagi and Mr Gopalan said.
India has to test a broad swathe of people for that to happen. But how do we know who India is testing? Comparing testing numbers across countries is tricky because some count how many people they test, while others count how many tests they do. India does the latter and this number is slightly exaggerated because most people get tested more than once.
So instead, scientists prefer to calculate how many tests it takes to find a single confirmed case. The more tests it takes, the wider you are casting your net. Here, India fares poorly compared to countries that have managed to control the spread of the virus.
And the more widely you test, the lower your positive rate – that’s why New Zealand and Taiwan have rates well below 1%.
India’s positive rate is now up from 3.8% in April to 6.4% in July. If it keeps rising, it’s because testing is still limited to a narrow pool of high-risk people and their contacts.
3. India’s recovery numbers are promising
The data suggests that those in India who have been diagnosed with the virus are recovering from it faster than they are dying from it.
This is crucial, Dr Jameel said, because it determines the strain on the health system. Currently, deaths are rising more slowly than confirmed cases or recoveries – but if that rate quickens, it would increase the pressure on hospitals, possibly driving up deaths.