As COVID-19 sweeps India, experts say cases and deaths are going unreported

India, home to the world's worst ongoing coronavirus outbreak, has reported more than 17.6 million cases since the pandemic began last year.

But the real number, experts fear, could be up to 30 times higher — meaning more than half a billion cases.

Health workers and scientists in India have long warned COVID-19 infections and related deaths are significantly underreported for several reasons, including poor infrastructure, human error, and low testing levels.

Some things have changed since then — testing has greatly increased in the wake of the first wave, for instance.

But still, the true extent of the second wave now ravaging India is likely much worse than official numbers suggest.

"It's widely known that both the case numbers and the mortality figures are undercounts, they always have been," said Ramanan Laxminarayan, director of the Centre for Disease Dynamics, Economics and Policy in New Delhi.

"Last year we estimated that only one in about 30 infections were being caught by testing, so the reported cases are a serious underestimate of true infections," he said.

"This time, the mortality figures are probably serious underestimates, and what we're seeing on the ground is many more deaths, than what has been officially reported."

CNN has reached out to the country's health ministry for comment about the claims of underreporting.

As the first wave began to ebb in September last year, the government pointed to its low death rate as a sign of its success in handling the outbreak, and to support its decision to lift some restrictions.

Prime Minister Narendra Modi celebrated the low figures as boosting "the confidence of people," and predicted "the entire country will emerge victorious in the battle against COVID-19," according to a press release in August.

That battle is still ongoing. The country's daily death toll is projected to continue climbing until mid-May, according to prediction models from the University of Washington's Institute for Health Metrics and Evaluations.

The death toll could peak at more than 13,000 a day — more than four times the current daily death toll, the predictions show.

"I don't think any family has been spared a COVID death," said Laxminarayan. "There's a missing person in every family that I can think of."

India's testing capacity has increased dramatically since the first wave. Around this time last year, the country was testing fewer than half a million people per day — now, "they are doing close to 2 million tests a day," said Dr Soumya Swaminathan, chief scientist for the World Health Organisation (WHO).

But "that's still not sufficient because the national average positivity rate is about 15 per cent — in some cities like Delhi it's up to 30 per cent or higher," she said on Monday.

"That means there are lots of people out there who are infected and not being detected just because of the capacity of testing ... we will know only later how many was really the number of people infected."

There are a few reasons for the insufficient testing, according to Bhramar Mukherjee, professor of biostatistics and epidemiology at the University of Michigan.

The most obvious is that asymptomatic patients — also called "silent infections" — may simply never know they were infected, and so never get tested.