[ad_1]
Highly contagious new variants of the coronavirus will emerge more frequently and trigger new waves of infection such as those threatening to overwhelm hospitals in the UK and South Africa, one of the world’s leading disease experts has warned. infectious.
Salim Abdool Karim, chairman of South Africa’s Covid-19 ministerial advisory committee, also said it was too early to know to what extent existing vaccines would provide immunity to new variants.
Scientists around the world have been alarmed by the rapid spread of the new 501.v2 variant first detected in South Africa and the equally infectious B.1.1.7 variant which has led to an increase in cases in the UK. United. Other variants have appeared recently in Brazil and Japan.
Professor Abdool Karim, the epidemiologist who has led the fight against HIV / AIDS in South Africa, explained that viruses evolve as they infect people with partial immunity in order to escape recognition by their families. antibody.
“We’re going to see this happen more frequently now than in 2020, as we vaccinate and more people are infected,” he said in an interview with the Financial Times.
The epidemiological finding of increased transmissibility was supported by “biological evidence showing that the 501.v2 variant binds more easily and more strongly to human cells,” added Professor Abdool Karim.
The Sars-Cov-2 virus that causes Covid-19 has mutated once or twice a month on average since its appearance in humans at the end of 2019. But the variants detected in South Africa and the UK carry around 20 mutations, where the previous ones had been associated. with one or two significant genetic changes.
A greater number of mutations can lead to a greater change in the behavior of the virus. The variants originating in the UK and South Africa are both around 50% more infectious than previous forms of the virus, although neither appear to cause more severe symptoms.
Another question is how the variants interact with the human immune system, particularly if they reduce the effectiveness of Covid-19 vaccines. “We will have an answer in the next two weeks, but we don’t know yet,” Prof. Abdool Karim said of the 501.v2 variant.
Antibodies from people who recovered from Covid-19 were less effective against the new variant, said Prof Abdool Karim, but “the way T cells and B cells work is quite different in vaccine immunity. I wouldn’t extrapolate natural immunity to vaccine immunity. “
Less is known about the new variant of Sars-Cov-2 detected in Brazil after scientists sequenced 180 viral genomes from the state of Rio de Janeiro.
Researchers from Brazil’s National Genomic Surveillance Network have identified a “significant increase” in cases of the variant that “raise concerns about public health management” in a country with more than 200,000 deaths linked to Covid-19 , the second highest number of deaths after the United States.
Carolina Voloch of the Federal University of Rio de Janeiro, lead author of a pre-print article on the variant, said samples taken in Rio state showed its frequency had increased from zero in September to 20 % in November.
“At the moment, we can’t say it’s more contagious. What we can say is that there is an increase in the frequency of this lineage, ”said Dr Voloch.
Japanese authorities have also detected a new variant in four passengers who arrived from Brazil on January 2. It is related to the B.1.1.248 variant of the virus circulating in Brazil and shares some of the same mutations as the British and South African variants. , according to the Japanese National Institute of Infectious Diseases.
But Emma Hodcroft, a viral geneticist at the University of Bern who is monitoring the progress of Sars-Cov-2, said: “It doesn’t look like these four cases from Japan are part of the larger Brazilian cluster.”
She agreed that conditions in 2021 were likely to favor the evolution of a greater number of variants with multiple mutations, as a greater proportion of people were infected and the evolutionary pressure on the virus increased.
A modeling study by scientists from Emory and Penn State, published Tuesday in the journal Science, suggested that the Sars-Cov-2 evolutionary pathway would eventually lead to a less virulent ‘endemic’ virus, joining the ranks other mild coronaviruses causing cold. that are currently circulating in humans.
“We are in uncharted territory though. . . Immunological indicators suggest that death rates and the critical need for large-scale vaccination may decrease in the short term, so maximum effort should be on resistance to this pandemic, ”said Ottar Bjornstad, a Penn State professor. .
Professor Abdool Karim also argued that selective pressure for all viruses must “become more transmissible and less pathogenic over time”.
Additional reports: Robin Harding in Tokyo and Carolina Pulice in São Paulo
Source link
