UK Prime Minister Boris Johnson announced last week that people infected with the coronavirus variant reported for the first time in the country may face a greater risk of death than those who contract the original virus.
“There is some evidence that the new variant may be associated with a higher degree of mortality,” he said at a news conference on Friday.
Studies have shown that the variant, known as B.1.1.7, is more contagious than its viral predecessors. But the evidence did not suggest that the strain was more deadly so far.
“Considering that an average of 10 out of 1,000 elderly people died with the old variant in the UK, this appears to have increased to 13 out of 1,000 people with the new variant,” said Patrick Vallance, the UK’s chief scientific advisor on Friday . He stressed, however, that the evidence remains “uncertain”.
Since then, some experts have pointed out that just because more people infected with this variant are dying does not mean that it is more lethal than other versions. It may be that the health care system in the UK is overburdened by the increase in coronavirus cases in the country, or that the increased transmissibility of the strain will allow it to infect more people with underlying health problems.
30% higher mortality rate, with reservations
Johnson’s announcement was based on research collected by the New and Emerging Respiratory Virus Threat Advisory Group (NERVTAG), which looked at differences in mortality between people in the UK who had been infected with B.1.1.7 and those with other strains.
After controlling for variables such as age, sex and geographic location of the patient, researchers at the London School of Hygiene & Tropical Medicine and Imperial College London found that, on average, people infected with B.1.1.7 had a 30% mortality highest rate.
A follow-up analysis by Public Health England analyzed data collected between 23 November and 4 January and found that B.1.1.7 was 65% more deadly than other strains. Meanwhile, researchers at the University of Exeter analyzed samples collected since October 1 and found that people infected with the variant were almost twice as likely to die.
However, the researchers found no evidence that people infected with B.1.1.7 were hospitalized at higher rates.
“If there is an increase in the severity of the infection,” wrote NERVTAG, “we also expect to see an increase in the risk of hospitalization.”
However, William Schaffner, an infectious disease specialist at Vanderbilt University, told Insider that it is possible that fewer people were going to hospitals for treatment, especially due to reports that hospitals in the UK were about to be overwhelmed.
‘Deaths will get out of control as your health system comes under pressure’
The World Health Organization said on Friday that it still needed to see the data that British authorities were using before confirming whether variant B.1.1.7 actually causes more serious illnesses.
If the strain is really more lethal, a potential reason could be that people infected with B.1.1.7 have higher viral loads, which means that they produce more viral particles when they are infected. Higher viral loads, several studies show, are associated with an increased risk of death and more serious illnesses.
“That was the first thing that certainly came to mind,” said Schaffner. “It would make a lot of sense.”
This could also explain the increase in contagiousness, because the more viral particles a person expels, the more likely they are to infect other people.
But it is also possible that the increased transmissibility of the variant is indirectly causing a higher mortality rate, although the strain itself is no longer deadly. B.1.1.7. it has several mutations in its spike protein code, which the virus uses to invade cells, which makes it between 50-70% more contagious than the original.
One of these possibilities is that, as there are many more cases in the UK, health systems are stressed and resources are scarce. This alone can lead to higher mortality rates.
“If their cases get out of hand, their deaths will get out of hand as their health system is under pressure,” said Mike Ryan, executive director of the WHO health emergency program, at a news conference on Friday.
It is also possible that the increase in the transmissibility of the strain ensures that the virus infects more people with a higher risk of serious diseases.
“It may not be because the virus itself is making any individual more likely to get severe COVID,” said Schaffner. “It may simply be a matter of a more contagious virus reaching more vulnerable people, older people or those with underlying health problems, such as diabetes or lung disease.”
A more communicable strain can result in a higher number of deaths than a more lethal strain
The UK researchers’ findings were based on just 8% of the total deaths in the UK during the study period, which is why Vallance still considers the evidence “not yet strong”.
“The results of all studies may therefore not be representative of the total population,” concluded NERVTAG.
To determine which strain infected and killed a person, scientists must genetically sequence a sample of the patient’s blood or saliva. The process takes time and samples collected from patients are not always sent for sequencing.
The data also failed to take into account any underlying health conditions in people who died of COVID-19, which could also distort mortality rates.
Regardless of the quality of the data, however, and regardless of whether the new strain is actually more lethal, its spread will almost certainly lead to a greater number of deaths in total, as infected individuals will spread it to more people.
Adam Kucharski, an epidemiologist at the London School of Hygiene and Tropical Medicine, compared three hypothetical scenarios on Twitter to demonstrate that.
Suppose the original coronavirus strain has a reproductive value (that is, the average number of people infected by a sick person) of 1.1 and kills 0.8 people in every 100 who get sick. In a population of 10,000 people, the virus would kill 129 people in one month.
But then let’s say that two new strains have emerged, one of which is 50% more lethal, while the other is 50% more transmissible. The strain that is 50% more lethal would kill about 193 of 10,000 people in a month. But the strain that is 50% more transmissible would end up causing 978 of the 10,000 people to die at that time because of its rapid spread.
Anna Medaris-Miller contributed to the reporting of this story.
Read the original article on Business Insider