Scientists in Japan say one in two sufferers of the new coronavirus may have been infected by a person with no symptoms at the time.

The study suggests the virus has the ability to spread significantly even during the incubation period.

A Hokkaido University research team led by Professor Hiroshi Nishiura analyzed the data of 52 patients from countries where a study to trace the virus has already been conducted, including China and Germany.

The group surveyed the period of time between the appearance of symptoms in a patient, and the appearance of the symptoms in another suspected to have been infected by them.

They found the average incubation period was 3.8 days -- shorter than the average of five days that has already been reported.

The scientists carried out further analysis using the hypothesis that each infected person transmits the virus to 2.2 people. They say it shows that one in two patients may have been infected by another person showing no symptoms.

The team said although the study was small, it illustrates the need for a medical framework that protects those who tend to develop severe symptoms, including the elderly and others with underlying conditions.