Researchers at Peking University’s School of Life Sciences and the Institut Pasteur of Shanghai say preliminary results show the virus that has killed more than 3,200 people across the globe has now split into two major lines.

The more aggressive strain, which has infected about 70 percent of those tested, has been dubbed the “L type”. It is the strain prevalent in the Chinese city of Wuhan, where the virus first emerged.

Meanwhile the less-infectious “S type”, which is older than its aggressive counterpart, was linked to the remaining 30 percent of cases.

Genetic analysis of a man in the United States who tested positive in January showed it is possible to be infected with both strains of the virus.

Those behind the study, published in the National Science Review, warned the data was still “very limited” and follow-up studies will be needed to get a clearer picture of the virus’s evolution.