- Researchers have identified a total of eight strains of SARS-CoV-2 and noted none of them appear deadlier than the other
- SARS-CoV-2 is the disease that is able to develop into COVID-19 which can range from mild to fatal symptoms
- Tracking the origin of SARS-CoV-2 has been difficult for researchers due to a lack of data from China over the first months of the outbreak
As the world continues to try and contain the spread of COVID-19, experts are working hard trying to learn more about the origin of the novel coronavirus. Researchers have so far discovered a total of eight strains of SARS-CoV-2 being transmitted globally. Luckily, none of them appear to be deadlier than the other.
With around a half-million cases in the world, researchers caution they are only seeing a glimpse into the pandemic as a whole. “Remember, we’re seeing a very small glimpse into the much larger pandemic. We have half a million described cases right now but maybe 1,000 genomes sequenced. So there are a lot of lineages we’re missing,” Kristian Anderson told USA TODAY.
Researchers around the world are using sequencing machines to sequence the genomes of COVID-19 samples taken from those infected. The data is then uploaded to NextStrain.org where scientists from around the world can use the data from academic, independent and government laboratories to track the genomics of SARS-CoV-2. These maps are now being passed around on Twitter and other social media sites, but even experts say phylogenetic trees showing the SARS-CoV-2 evolution are complex and extremely difficult to form a conclusion.
All eight strains of SARS-CoV-2 can lead to the development of COVID-19. The difference in symptoms can cause anything from mild symptoms to critical care in people of all ages. The death rate — believed to be around 1% — varies from country to country but experts believe that is related to the testing rates, not the mortality rates.
SARS-CoV-2 mutates very slowly, which helps with the tracking of current strains. Since the virus mutates so slowly, the different strains stay very similar fundamentally to previous strains. At this point, there are no major concerns that it will evolve into something more deadly. SARS-CoV-2 is highly contagious in humans and has no evolutionary pressure on it to evolve into a deadlier form.
As of now, the SARS-CoV-2 can be traced back to China sometime between mid-November and mid-December. While the theory that SARS-CoV-2 was man-made has been entertained, it is accepted by the vast majority of the scientific community the disease evolved from an animal host. The genomic molecular structure of SARS-CoV-2 is closest to a coronavirus found in bats. A study in the Nature Medicine journal found that it is improbable that SARS-CoV-2 was created through a laboratory by manipulating a related SARS-CoV-like virus. The genetic data irrefutably shows that SARS-CoV-2 is not derived from any known previous virus backbone.
Due to the similarity between SARS-CoV-2 and SARS-CoV-like coronaviruses found in bats, it is likely a bat was the initial host. Although found to be 96% identical, the genomic molecular structure suggests that a coronavirus found in a bat may not bind efficiently to a human. In the Guangdong province of China, Malayan pangolins — a scaly anteater found throughout southeast Asia — are known to be illegally imported in and bring with them coronaviruses similar to SARS-CoV-2.
The study also found that a SARS-CoV-2 animal host possibly jumped into humans and began acquiring genomic features by adapting through undetected human-to-human transmission. Once those adaptions were acquired, everything was in place to spawn a pandemic with clusters large enough to trigger the surveillance system that first detected the outbreak. The two theories mean that current data shows either natural selection occurred in humans before a zoonic transfer, or natural selection occurred in humans following the zoonic transfer. Experts say SARS-CoV-2 could have originated from a single event, one transfer from a single animal to a single human and spread from there.
Unfortunately, researchers do not have a lot of genomic data from China beyond knowing it was first identified in Wuhan sometime between mid-November and mid-December. Yong-Zhen Zhang published the initial sequence on January 10, at the Shanghai Public Health Clinical Center. Scientists are still not sure if there was only one strain circulating in China due to a lack of data. It is still not clear if China neglected sequencing cases for political reasons or because they were simply not made available. This makes tracing SARS-CoV-2’s origin more difficult as data is missing from all the possible early strains. Several of the strains may have mutated inside of China before being discovered in other areas of the world. Researchers in the United Kingdom who sequenced the viruses found in travelers from Guangdong confirmed their strains spanned across the globe.
Even with the missing data, researchers are still able to track the current strains due to the slow mutation rates. For example, the majority of cases seen on the U.S. West Coast are linked to a strain first identified in Washington State. It is possible the strain possibly came from a man in his 30s that lived in Snohomish County, Washington. The unidentified man returned from a trip to Wuhan in early January and later became the first known confirmed case in America. The strain found in the man was only three mutations from the first identified strain spreading throughout Wuhan. On the opposite side of the U.S., the East Coast has become home to several strains, including the one from Washington. Other strains appear to have originated from, China, Europe, New York, and other unknown areas.