New Delhi: India is witnessing a setback in testing coronavirus in cluster areas due to unavailability of serological test kits as "some consignments have been diverted to the US", sources in Indian Council of Medical Research (ICMR) admitted on Sunday.

"The states have complained to us. This survellience test would have helped us lift lockdown from clusters and districts," a scientist within ICMR said, adding that it is a setback to the lockdown.

Serological tests use small amounts of blood, usually from a finger prick, to test whether a person has been exposed to a particular pathogen, like the new coronavirus, by looking at their immune response.

An official from the health ministry, on condition of anonymity, said that over 90 doctors and para-medic staff across the country have been affected due to unavailability of test kits. However, this could very well be a conservative figure given the fact that Maharasthra in itself has close to 90 medical staff infected.

The geographical spread of the infection has increased in 80 districts. The spread now is in 364 districts. The last four days saw spread in 80 new districts.

Both India and the US have been battling to contain the spread of deadly coronavirus. While India has been locked down till April 14, with the Centre mulling to extend the curb, the US — which has overtaken taken Italy and China with over 20,000 deaths — has requested New Delhi to help it by lifting ban on export of drugs.

A consignment of hydroxychloroquine from India on Sunday reached the US, the global covid-19 hotspot, days after India lifted a ban on the export of the anti-malarial drug to America on humanitarian grounds.

The Centre has also approved list of 13 countries that will receive coronavirus-fighting drugs from India, including HCQ. Besides US, the first list includes Spain, Germany, Bahrain, Brazil, Nepal, Bhutan, Afghanistan, Maldives, Bangladesh, Seychelles, Mauritius and the Dominican Republic.