"The study shows that virus is mutating very rapidly. In simpler words, we can say the virus is changing its structure quickly...which means it will be difficult to develop a vaccine for prevention from this dreaded virus.

"Even if we develop a vaccine, we are not sure that the same vaccine will work in other parts of the world, looking at the nature of different strains of COVID-19," said Lal, a senior scientist with The Energy and Resources Institute(TERI).

On why people are dying more in Spain, Italy and now in the US, scientist Vipin Gupta, a key member ofLal's team said in their study it was discovered that virus which changed itself rapidly in Europe and then in the US, was more devastating.