Nov. 22 in New Delhi Japanese scientists have found that the virus that caused Covid-19, SARS-CoV-2, has an enzyme that can stop a cell’s natural defense system from fighting viruses.

Researchers from Kobe University said this could explain why Covid-19 is more contagious than the viruses that caused SARS and MERS in the past.

The researchers were most interested in a part of the Covid virus called “ISG15.” This part stops nucleocapsid proteins from binding to each other, which is an important step for viruses to put themselves together.

A virologist from the university named Shoji Ikuo wrote in the Journal of Virology that the enzyme can also remove the tags from its nucleocapsid, which restores its ability to put together new viruses and defeats the body’s natural defense system.

The ISG15 tag can also be removed by the SARS and MERS viruses, but Shoji’s team found that these viruses are not as good at it.

“The results suggest that the novel coronavirus is just better at getting around this part of the innate immune system’s defense mechanism,” Shoji said. “That’s why it is so contagious.”

The first line of protection against pathogens is the natural immune system, which stops viruses from entering, copying themselves, and putting together viruses. It also finds sick cells and gets rid of them.

Unlike the SARS and MERS viruses, Covid quickly spread to almost every region, even Antarctica, which doesn’t have many people living there. The Covid virus keeps changing and spreading new types of itself. The intensity has gone down, though, thanks to group protection and mass vaccines.

The new information could help make drugs that work better against Covid-19 and maybe even diseases like it in the future.

“If we can stop the viral enzyme that removes the ISG15 tag from working, we might be able to make new drugs that fight viruses.” Researchers said that in the future, antiviral drugs that directly target the nucleocapsid protein or a mix of these two methods could be used as treatments.