A new study on SARS-CoV-2, also known as the new coronavirus, suggests there are two strains of the virus in humans. The work is preliminary with only 103 samples, but if confirmed it will provide a better framework for treatments and vaccines.
The potential discovery was published in the National Science Review, the journal of the Chinese Academy of Sciences. Researchers report that they have discovered two strains of the virus circulating in humans. They differ by just a couple of nucleotides among tens of thousands. The team believes they have identified an older type dubbed “S” that is less aggressive and a more recent one, called “L”, which appears to better at spreading and causing the COVID-19 disease.
The team reports that the S type was found in 30 percent of the cases analyzed, with the remaining 70 percent being L type. They also think that the L type was the most prevalent strain at the beginning of the Wuhan outbreak, but its frequency began to decrease from early January. Human intervention may have pushed this strain to become more aggressive.
“It is usually the case that when RNA viruses first cross species barriers into humans they aren’t particularly well adapted to their new host (us!). Thus, they usually undergo some changes allowing them to adapt and become better able to replicate within, and spread from human to human,” Dr Stephen Griffin, associate professor at the Section of Infection & Immunity, University of Leeds, told the Science Media Center. “However, as this study hasn’t tested the relative 'fitness' of these viruses when they replicate in human cells or an animal model, it isn’t really possible to say whether this is what’s happened to SARS-CoV2. It is also difficult to say how/why human interference may have impacted upon one strain relative to the other for similar reasons.”
The team called for further and more comprehensive study combining genomic analysis of the virus with epidemiological data as well as clinical symptoms to make sure that if there are indeed two different strains, researchers and medical professionals are well-equipped to find the most successful treatments.
"I’m not sure that you can reasonably say yet whether this variability is linked to viral decline, or could be used to tell whether someone is likely to succumb to the virus – this second question is almost certainly due to a balance between the virulence of the virus, host genetics, age, underlying conditions, immune status and environmental factors," added Griffin.
As of March 3, there have been 90,870 confirmed cases of COVID-19 across 73 countries. The number of deaths has now surpassed 3,000.