The new coronavirus is capable of mutating quickly and several strains could explain the different impacts around the world.
Professor Li Lanjuan and colleagues from Zhejiang University also found direct evidence that some mutations could create more lethal strains than others.
The team took viral strains from 11 randomly selected COVID-19 patients in Hangzhou and tested the effectiveness with which they could infect and kill cells, reports the SCMP.
Researchers have observed “various mutations” among the viral strains, including one that generates 270 times more viral load than the least potent type.
Strains of the virus that create high viral loads are more dangerous.
The deadliest strains have been detected in Europe and the United States, which is one of the most affected countries in the world.
Weaker mutations still pose a threat to humans, with at least two Chinese patients becoming extremely sick. ICU treatment was needed.
The study, published on Medrvix, showed that “mutations can have a direct impact on viral load”.
The researchers “observed abundant mutational diversity, including several founding mutations of different large groups of viruses that are currently circulating around the world.”
The generic researchers noticed differences between the strains in different geographic areas.
The mystery of the variation in mortality rates was complicated by factors such as the patient’s age, health status and blood group.
The results mean that the true diversity of viral strains may have been largely underestimated.
Hospitals generally treat patients with COVID-19 as if they have a disease, but the mutations mean that a different response may be needed.
The study has implications for the development of drugs and vaccines, which will need to take into account mutations in the virus.
The sudden outbreak of severe acute respiratory syndrome coronavirus (SARS-CoV-2) – which causes COVID-19 – has infected more than 2.4 million people worldwide.
Nearly 170,000 deaths have been recorded since the start of the epidemic, which was first detected in Wuhan, China.
COVID-19 can be transmitted by asymptomatic patients, who do not have fever, gastrointestinal or respiratory symptoms, making prevention of spread much more difficult.
It can also remain infectious in aerosols for several hours and up to seven days on surfaces.
So far, no vaccine or effective cure has been found.