A small study convincingly shows that coronavirus may have more mutations than previously expected, but more data is needed on whether these mutations actually change how deadly the virus is.
Key takeaways
- Though this study only used samples from 11 patients, it was well designed and used super deep sequencing technique to show that the coronavirus has more mutations than previously thought.
- The data on how quickly the virus reproduces and how deadly it is needs much more testing and verification to see if this is true outside of a petri dish. We wouldn’t put too much stock in this finding just yet.
- Finding live virus in patient’s stool is a new finding that merits further investigation
Why is this important?
This research is important for a couple reasons. Figuring out what mutations there are and how quickly the coronavirus mutates is important for researchers working on treatments and vaccines so that they can target the right areas of the virus. Second, if different strains of the virus are more infectious or more lethal than others, this could help different countries and regions better manage their outbreaks.
This study has recently been taken up by media outlets, mainly focusing on the possibility that mutations might make some strains of the coronavirus more deadly than others. Let’s take a look at those claims.
What did the study do?
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Sampling
Extracted live virus samples from 11 patients
The 11 patients came into the researchers' hospital in China in January 2020, and were confirmed to have coronavirus. The researchers found that they were able to isolate functioning viral particles from poop 💩
Our Take
Functioning viruses in poop is an exciting finding
Finding active coronavirus in poop is a new finding that should be further investigated, as it may affect how people protect themselves from contracting the virus.
Only one sample per patient
Growing the virus can vary a lot from sample to sample so generally researchers try to take multiple samples from the same patient or samples from multiple patients who have similar strains of the virus to make this process more reliable. In this study, the researchers only took a single sample from each patient, and every patient had a different strain of the virus.
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Testing
Identified 33 total mutations with 19 brand new mutations between the virus samples
This was a two part study. In the first part, they isolated coronavirus from these patients and determined if they had any mutations in their genome using deep sequencing.
Our Take
Excellent deep sequencing techniques
The researchers have excellent evidence to show how much the virus mutates. The genetic sequencing technique they used was more sensitive and of higher quality than prior studies, which allowed them to pick up more mutations.
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Measuring
Fastest growing samples of the virus grew 270 times faster than the slowest
In the second stage, they grew the different strains of virus in the lab and measured how rapidly the strains could reproduce in cells growing in a dish, and then how fast the virus killed those cells.
Our Take
Lack of standardization in virus sampling
A challenge in virus research is making sure you have the same amount of live virus in each sample because this can make a huge difference in the results.
Example: Let's say a sample has 100 virus particules, but only 20 of them are living 1.
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Sample A
Meanwhile, another sample has only 50 virus particles, but all 50 of them are living.
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Sample B
Standardizing between both samples before you start measuring how quickly they kill cells is super important because you could mistakenly conclude that sample B is more deadly when really it just started with more living virus particles.
There are techniques for balancing these differences out, but the researchers don't provide any detail on whether or how they did this.
Samples grown in monkey cells, not humans
The cells that the authors used in the study were monkey kidney cells, which are commonly used in studies of viruses, and specifically for coronaviruses like SARS and the current coronavirus. It's always challenging to know if these findings would apply in living humans.
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Conclusion
SARS-CoV-2 mutates more than we had previously thought, and different strains of the virus might reproduce and kill cells at different rates
Our Take
The authors have not demonstrated that the mutations that they detected actually changes how sick humans get. The data on how quickly the virus reproduces and how deadly it is needs much more testing and verification to see if this is true outside of a petri dish. We wouldn't put too much stock in this finding just yet.
Small sample size
Since they only took samples from 11 patients who were all very different (their ages alone ranged from 4 months to 62 years), it is impossible to say if the mutations are why some were sicker than others. This would require a lot of data and further study.