A specific mutation in the new coronavirus can significantly increase its ability to infect cells, according to a study by US researchers, Reuters reported.

The research may explain why early outbreaks in some parts of the world did not end up overwhelming health systems as much as other outbreaks in New York and Italy, according to experts at Scripps Research.

The mutation, named D614G, increased the number of “spikes” on the coronavirus — which is the part that gives it its distinctive shape.

“The number or density of functional spikes on the virus is 4 or 5 times greater due to this mutation,” said Hyeryun Choe, one of the senior authors of the study.

The researchers say that it is still unknown whether this small mutation affects the severity of symptoms of infected people, or increases mortality.