A fast and easy paper-strip test for Covid 19, much like a pregnancy test, is set to hit the market, and it could be a game changer for India as it seeks to curb the coronavirus pandemic.

The idea was first sparked over a cup of tea by its inventors.

In January, when India reported its first coronavirus case, chemical biologist Souvik Maiti, 49, and molecular biologist Debojyoti Chakraborty, 35, thought of re-engineering their paper-based test developed to detect sickle cell anaemia, a red blood cell disorder, for Covid 19.

Both of them are based at the Delhi-based Council of Scientific and Industrial Research's Institute of Genomics and Integrative Biology, and had been working on their invention for over two years.

The Covid-19 test prototype was ready in two months, said Dr Maiti.

They named the test Feluda - for FNCAS9 Editor-Limited Uniform Detection Assay - and in a nod to a much loved fictional detective of the same name created by film director and writer Satyajit Ray.

By May, the Tata Group, a leading Indian conglomerate, had been chosen to manufacture the testing kits, which received approval from India's drug authority last month.

"In a couple of weeks, we will have the product in the market," said a Tata Sons spokesman.

The test, which provides results in less than an hour, is based on a technology called CRISPR-Cas, which can detect genes specific to the coronavirus.

"It will be cheaper, much faster and easier," said Dr Maiti.

He said the test required only a PCR (polymerase chain reaction) machine, which is commonly found in labs and colleges. Battery-operated versions of the machine mean it is highly portable.

"No (other) special equipment is required. That's the beauty of this test. To perform the test, you need a simple machine with low-trained manpower. You don't need a lab technician. You can deploy this in low-resource areas like Ladakh and other remote parts of the country."

An early estimate for the kit puts it at 500 rupees (S$9.30), but it will likely be priced higher when it reaches the market.

India is the second-most affected country in the coronavirus pandemic, after the United States. It has 7.2 million cases, with 110,586 deaths. On Tuesday, 63,509 new confirmed cases were recorded amid a downturn in new cases.

The South Asian country has ramped up testing from 1,000 a day in March to 1.1 million per day now.

Testing is crucial for the country of 1.35 billion people, as early detection helps to curb transmission.

At present, India uses two types of tests. One is the RT-PCR (reverse transcription-polymerase chain reaction) test, which takes anywhere from four hours to a day for results and is considered the gold standard of testing. Such a test can cost up to 4,500 rupees.

The second is the rapid antigen test, which gives results within 30 minutes and is cheaper, costing not more than 750 rupees per test. But it is also seen to be unreliable, given the high rate of false negatives.

It is not known how many rapid antigen tests are administered, which only fuels concerns that coronavirus case numbers in the country are being under-reported. Serological surveys have shown that many more were infected than the official estimates had suggested.

The paper strip test has so far shown an accuracy rate close to that of the RT-PCR test.

During trials, tests of more than 2,000 patients showed 96 per cent sensitivity and 98 per cent specificity.

Experts said the paper test could be a game changer.

"If they have said it is more accurate than the antigen test and is quicker and cheaper, it would be beneficial," said epidemiologist Jayaprakash Muliyil.

"This one may be able to replace the antigen testing."

India has seen other innovations since the coronavirus pandemic hit the country. They range from a toaster-sized ventilator to pooled testing to detect the virus in large populations.

The Feluda test has already ignited international interest, with inquiries about the test and its availability coming in from countries around the world.

"India's scientific institutions are responding to the pandemic with innovation on the fast track. Feluda is a product that testifies to their strength," said Professor K. Srinath Reddy, president of the Public Health Foundation of India.

"The innovation must, however, prove its mettle in the field. We wait eagerly for the evidence of how this promising batsman performs on the field after stepping out of the dressing room," he said.

"If it performs nearly as well in field settings, it can be a game changer for early case detection."