SARS CoV-2 Variants Are Rapidly Changing the Pandemic's Direction
On January 28, public health professionals announced that two South Carolina residents were found to be infected with the South Africa strain of the COVID-19 virus. The day before, a Minnesota resident was found to be infected with the Brazilian strain of the virus. Epidemiologists, vaccine manufacturers and public health professionals want to know how these variations of the virus are changing the trajectory of the pandemic.
SARS CoV-2 Mutation Allowed It to Infect Humans
Sometime in late 2019, the SARS CoV-2 mutated. It gained an ability to alter its spike protein. Scientists think this happened when the virus infected an animal that was infected with other viruses. The spike protein mutation allowed the SARS CoV-2 to get inside human cells by hijacking an enzyme called furin. This enzyme is like a pair of scissors. It cuts open the spike, which allows the virus's genetic material to zoom right into the cell. This mutation allowed the SARS CoV-2 to be more infectious and transmissible to humans. It also differentiated this coronavirus from the hundreds of other coronaviruses that circulate among people and animals.
Why This Mutation Was Important
The furin mutation allows the SARS CoV-2 virus to enter human respiratory cells and burrow deeper into tissues. Once the virus was easily able to infect people, it began to infect a lot of them. Each time the virus goes through a new person, it develops new mutations. Some of those mutations are proving to be important because they increase transmission or virulence of the virus.
What Mutations Mean for the Pandemic
Some mutations involve a swap. Others involve an addition or deletion of an amino acid. Most of them will have minimal effect. Some will decrease the virus's vitality. Others will enhance its ability to infect and sicken people. Some mutations alter how quickly the virus spreads, how infectious it is or the severity of the illness it causes.
Increased Viral Shedding
One important mutation allows the SARS CoV-2 virus to make more copies of itself. This increases viral shedding. When a person coughs or sneezes, they release more virus into the air. This mutation drove the rapid increase in COVID-19 cases in Europe in early 2020. The mutation was in the spike protein. It is called D614G, and it enabled a faster spread between people.
New British and Spanish Variants Also Increase Transmission Rates
In June 2020, a SARS CoV-2 variant was detected in Spain. By September, it was the dominant strain in Ireland, Switzerland and the UK. Its mutation allowed it to increase the effectiveness of the protein's ability to get into the cell. In Scotland in March 2020, another mutation caused a similar effect, but a strict lockdown halted the spread of that strain. Also in the UK, the H69/V70 deletion mutation boosted infectiousness by 100%. This mutation is also on the virus's spike protein.
Another British Variant Develops
A recent concern among scientists is the B117 variant of the coronavirus. It also features the H69/70 deletion, but it has acquired an additional 16 mutations on its spike protein. One involves the furin enzyme. It allows the virus to bind more tightly to human cells. Scientists state that this variant replicates twice as fast than the original strain from Wuhan, China. Researchers expect it to be the dominant strain in the United States by March 2021.
How So Many Mutations Developed in the British Strain
Scientists think that the strain with 17 mutations occurred in someone with a chronic infection. This gave the virus more time to make errors as it replicated. The original patient with the strain was receiving treatment for cancer. Those treatments reduce immune system capabilities.
Public Health Response to Variants
A short-term study found that the B117 variant is 30% deadlier than the original strain. More data and peer reviewing are needed to confirm this. A South African strain has also caused a rapid rate of spread. In Brazil, a new strain increased both transmission and mortality rates in recent weeks. Public health officials have responded with more lockdowns and travel restrictions. Scientists have also found that the variants can cause a reinfection in a person who has already had the original strain of COVID-19. This could add to the burden of caring for sick people and affect the plans for vaccinating people who have been infected by any strain of the virus.
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