A team of researchers has discovered one reason that likely makes SARS-CoV-2, the virus that causes Covid-19, so much more infectious than SARS-CoV-1, which caused the 2003 SARS outbreak.

The coronaviruses that cause SARS and Covid-19 have spike proteins that move into 'active' and 'inactive' positions, and the study indicates how those molecular movements may make the Covid-19 virus more infectious compared to the SARS virus, according to researchers, including one of Indian-origin named Vivek Govind Kumar.

"We discovered in these simulations that SARS-CoV-1 and SARS-CoV-2 have completely different ways of changing their shape, and on different time scales," said researcher Mahmoud Moradi from the University of Arkansas.

"SARS-CoV-1 moves faster, it activates and deactivates, which doesn't give it as much time to stick to the human cell because it's not as stable. SARS-CoV-2, on the other hand, is stable and ready to attack," he added.

The researchers explained that the first step in coronavirus infection is for the virus to enter cells. For this entry, the spike proteins on the outside of the SARS-CoV virus must reposition.

Scientists know the position of the "inactive" and "active" states of the spike proteins of both the SARS-CoV-1 and -2 viruses, but the team wanted to study how the spikes moved from one position to another and the dynamics of those movements.

For the study, presented at the 65th Annual Biophysical Society Meeting, the team turned to molecular simulations.

The other implication for their research is "we could design therapeutics that alter the dynamics and make the inactive state more stable, thereby promoting the deactivation of SARS-CoV-2. That is a strategy that hasn't yet been adopted," Moradi explained.

It is valuable to be able to do these kinds of simulations, Moradi said, in the event a new coronavirus emerges, or SARS-CoV-2 mutates so that they can predict if the new virus or variant could be higher in transmissibility and infection.