Scientists in China studying the viral disease outbreak’s origin said they had found that two main types of the new coronavirus could be causing infections.

The researchers, from Peking University’s School of Life Sciences and the Institut Pasteur of Shanghai under the Chinese Academy of Sciences, cautioned that their analysis examined a limited range of data, and said follow-up analyses of larger data sets are needed to better understand the virus’s evolution.

The preliminary study found that a more aggressive type of the new coronavirus associated with the disease outbreak in Wuhan accounted for about 70 per cent of analysed strains, while 30 per cent was linked to a less aggressive type.

The prevalence of the more aggressive virus decreased after early January 2020, they said.

“These findings strongly support an urgent need for further immediate, comprehensive studies that combine genomic data, epidemiological data, and chart records of the clinical symptoms of patients with coronavirus disease 2019 (COVID-19),” they wrote.

Their findings were published on Tuesday in the National Science Review, the journal of the Chinese Academy of Sciences.

The findings come amid a fall in new coronavirus cases following crippling restrictions imposed on the world’s second largest economy to stop its spread, including transport suspensions and the extension of the Lunar New Year holiday.

Mainland China had 119 new confirmed cases of coronavirus on Tuesday, the National Health Commission said, down slightly from 125 the previous day, in a broad trend that has seen numbers of new cases fall from the middle of February.

The total number of cases on the mainland has now reached 80,270. The number of deaths rose by 38 to bring the total toll for mainland China to 2,981 by March 3.

All but one new death occurred in Hubei province, the epicentre of the outbreak.

With the number of new daily infections overseas now exceeding new cases in China, Chinese officials have begun to seek ways to control the spread of the virus outside China and guard against future outbreaks.

Authorities have asked overseas Chinese hoping to return home to reconsider their travel plans, while cities across the country have set up quarantine rules for those entering from high-risk places.

Italy, South Korea and Iran have all become infection hot spots. An infected person is known to have arrived in China from Iran last week.

Italy closes schools

All Italian schools and universities will close from Thursday until March 15 as part of an effort to contain a growing outbreak of coronavirus, education minister Lucia Azzolina said on Wednesday. The death toll in Italy jumped by 28 over the past 24 hours to 107.