News24xx.com - A mutated version of the coronavirus that has gripped Europe and the West is more infectious because it doesn't break as often while inside the body, a study has found.
Researchers at The Scripps Research Institute in Florida say the 'spike protein' that the virus uses to attach to cells in the airways has adapted since January.
It used to break off regularly while trying to bind to receptors in people's airways, which it would use to gain entry to the body, but is now more resilient, they say.
A genetic mutation which scientists around the world have been picking up on for months appears to have caused this spike to be less likely to snap, and also to force the coronaviruses to produce more of them to make itself more infectious.
As a result the virus appears to be approximately 10 times more infectious than it was when it first jumped to humans in China at the end of the year, scientists say.
The mutated version of the virus, dubbed G614 - a change from D614 - is a tiny change in its genetic make-up that scientists weren't sure what to make of when they found it.
But by May research had found it had become the dominant strain being found in Covid-19 patients across the UK, US, Canada and Italy.
Lead researcher on the Scripps institute's study, Dr Hyeryun Choe, told the Washington Post the mutation seemed to have happened to 'compensate' for the weakness of the spike protein in the past.
The Post reported it appeared to have become approximately 10 times more infectious as a result of this change.
The way the virus enters the body is by using its spike to latch onto a receptor - called an ACE-2 receptor - inside someone's airways.
ACE-2 receptors are essentially tiny gateways that the virus uses to get into the blood and then multiply rapidly, destroying cells around them in the process and triggering illness.
Dr Choe and her colleagues examined the differences between the spike proteins, dubbed S, on the outside of both versions of the coronavirus.
They found: 'These results show SG614 is more stable than SD614, consistent with epidemiological data suggesting that viruses with SG614 transmit more efficiently.'
The spike was stronger, they said, and as a result the virus was better able to bash through the gateway of the ACE-2 receptors.
Dr Choe told the Washington Post: 'The epidemiological study and our data together really explain why the [G variant's] spread in Europe and the US was really fast... This is not just accidental.'
However, this improved spike strength did not seem to be making people any sicker - or any less sick.
This, they suggested, could be because the spike had nothing to do with the virus's ability to reproduce - to replicate - once it was inside the body.
HOW AND WHY CAN VIRUSES CHANGE OVER TIME?
Viruses are known to change over time because they are subject to random genetic mutations in the same way that all living things are.
These mutations can have various effects and many will only happen briefly and not become a permanent change as newer generations of viruses replace the mutated ones.
However, some of the mutations might turn out to be advantageous to the virus, and get carried forward into future generations.
A virus may change its structure by accident but turn out to be more infectious that way, meaning it can infect more hosts, reproduce more, and become more dominant than its less fertile predecessor.
Or if a virus becomes less dangerous to its host - that is, it causes fewer symptoms or less death - it may find that it is able to live longer and reproduce more.
As a result, more of these less dangerous viruses are produced and they may go on to spread more effectively than the more dangerous versions, which could be stamped out by medication because more people realise they are ill, for example.
The mutation may then be taken forward in the stronger generations and become the dominant version of the virus.
In an explanation of an scientific study about HIV, the NHS said in 2014: 'The optimal evolutionary strategy for a virus is to be infectious (so it creates more copies of itself) but non-lethal (so its host population doesn’t die out).
'The "poster boy" for successful long-living viruses is, arguably, the family of viruses that cause the, which has existed for thousands of years.'
The process of reproduction, and using the body's resources to achieve this, is how the coronavirus causes illness.
Dr Choe's study added: 'An interesting question is why viruses carrying the more stable SG614 appear to be more transmissible without resulting in a major observable difference in disease severity.