The most common strain of the Covid-19 coronavirus is far more aggressive than its counterpart.

The most common strain of the Covid-19 coronavirus is far more aggressive than its counterpart. Reuters


  • Mainland China reports 38 new deaths by Wednesday morning, a rise from the previous day’s count, but new infections fall again to 119
  • Champions League and Europa League matches in Spain to be held behind closed doors


March 4 2020

The coronavirus has evolved into two major types, with differing transmission rates and geographical distribution, according to a study published in the National Science Review on Tuesday.

A group of Chinese scientists analysed 103 coronavirus genomes and identified mutations in 149 sites across the strains.

They found that one type, which they called the L type, was more prevalent than the other, the S type, meaning it was more infectious. They also found that the L type had evolved from the S type, and that the L type was far more widespread before January 7 and in Wuhan, ground zero of the outbreak.

Human actions soon after the outbreak was discovered in December may have changed the abundance of each type, the report said, citing the Chinese central and local governments’ drastic containment measures including lockdowns of cities, which it said may have curbed the spread of the L type.

The SARS-CoV-2 epidemic started in late December 2019 in Wuhan, China, and has since impacted a large portion of China and raised major global concern.

Herein, we investigated the extent of molecular divergence between SARS-CoV-2 and other related coronaviruses.

Although we found only 4% variability in genomic nucleotides between SARS-CoV-2 and a bat SARS-related coronavirus (SARSr-CoV; RaTG13), the difference at neutral sites was 17%, suggesting the divergence between the two viruses is much larger than previously estimated.


Our results suggest that the development of new variations in functional sites in the receptor-binding domain (RBD) of the spike seen in SARS-CoV-2 and viruses from pangolin SARSr-CoVs are likely caused by mutations and natural selection besides recombination.


Population genetic analyses of 103 SARS-CoV-2 genomes indicated that these viruses evolved into two major types (designated L and S), that are well defined by two different SNPs that show nearly complete linkage across the viral strains sequenced to date.


Although the L type (~70%) is more prevalent than the S type (~30%), the S type was found to be the ancestral version.

Whereas the L type was more prevalent in the early stages of the outbreak in Wuhan, the frequency of the L type decreased after early January 2020.

Human intervention may have placed more severe selective pressure on the L type, the  more aggressive and spread more quickly.

On the other hand, the S type, which is evolutionarily older and less aggressive, might have increased in relative frequency due to relatively weaker selective pressure.

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).

Keywords: SARS-CoV-2, virus, molecular evolution, population genetics


Chinese scientists say the novel coronavirus has mutated into two strains – one more aggressive than the other – in a discovery that could make developing a vaccine more difficult.

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 (ancestral) 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 and spread.

New cases down in South Korea, mainland China

South Korea on Wednesday confirmed 435 new cases of the coronavirus  down from 851 a day earlier, taking the country’s  total infections to 5,621
– the world’s largest after China. It reported four new deaths as the country’s toll reached 32.

Mainland China’s new daily cases continued to drop as it reported 119 infections, but the day’s new reported deaths jumped to 38, from 31 a day earlier, bringing its total fatalities to 2,981.

Transmission by faeces and urine recognised

The spread of infection through faeces and urine has been recognised as an additional mode of transmission in China’s latest coronavirus diagnosis and treatment plan.


Citing research in which traces of coronavirus were found in patients’ stool samples, the NHC’s plan added contact with and aerosolisation of contaminated faeces and urine as transmission modes. Aerosolisation refers to conversion into particles small enough to be carried in the air.

Chinese health authorities have said that respiratory droplets and close contact with infected people are the main ways the coronavirus is spread. The NHC added in its previous treatment plan that aerosol transmission was possible for those in a relatively closed environment for long periods.