Travel bans aren’t an effective response to the new Covid variant | Coronavirus | The Guardian
▻http://www.theguardian.com/commentisfree/2020/dec/23/travel-bans-effective-new-covid-variant
▻https://i.guim.co.uk/img/media/3fc38dc8a262b29c7508fb76bf884972d269e455/0_199_3500_2102/master/3500.jpg?width=1200&height=630&quality=85&auto=format&fit=crop&overlay-ali
Chris Whitty, the chief medical officer for England, announced that the variant, called B.1.1.7, is up to 70% more transmissible based on modelling studies. B.1.1.7 caused many infections in south-east England in a short period of time, rapidly displacing other circulating variants. Patients infected with B.1.1.7 also had higher viral loads. While this is certainly concerning, and warrants urgent scientific investigation, data supporting that this variant alone is driving the associated increase in cases is preliminary and inconclusive. Nonetheless, politicians began implementing sweeping policies right away.
Multiple countries have imposed travel bans, greatly reducing travel from the UK or blocking it entirely. France closed its borders to most freight transport. New York’s governor, Andrew Cuomo, called on the US government to impose numerous restrictions, including banning travel from Europe. He later settled for mandatory rapid testing for all travellers on US-bound flights from the UK.
Given the high prevalence of all variants of Sars-CoV-2, including in the UK and many countries abroad, imposing onerous travel restrictions alone is unlikely to make a significant impact in the overall pandemic. Furthermore, they may be too late. The B.1.1.7 variant has been reported in other European countries, as well as in Australia. These policies appear to be based more on the fear of variants with unknown properties rather than the actual data, and are due to a persistent and fundamental misunderstanding of viruses and how they evolve and change when spreading through a population.
Genetic mutation, the process that drives all evolutionary adaptation, is normal and expected, particularly for viruses. Every time the virus copies its genetic material – called its genome – it can make a mistake. If that mistake isn’t corrected, it will be copied the next time the virus replicates its genome. Mutations occur by chance, but if they happen to occur in a critical place and give the virus an advantage that allows it to outcompete other viral variants, they are said to be under positive evolutionary selection. For example, mutations in the spike protein of Sars-CoV-2, which allows the virus to enter and infect cells, can be selected for if they make the virus more efficient at establishing an infection.
We can probably expect to see other variants that may be more effective at spreading, causing disease or circumventing our immune responses. We must be prepared to respond in an informed and thoughtful way, rather than reactively. Unfortunately, because Sars-CoV-2 is spreading so widely, the virus has many opportunities to develop mutations that give it a competitive advantage. The only way to stop the virus from mutating is to take away its ability to replicate, which means drastically reducing community transmission.
Mutations do not automatically make a virus a more exceptional pathogen. The advantages conferred by positively selected viral mutations are good for the virus, but aren’t necessarily always bad for the human host. Many mutations can make the virus better at infecting cells, replicating, or transmitting to new hosts, but will have no effect on the severity or type of disease that they cause. In the case of B.1.1.7, there is fortunately no indication that the 23 mutations distinguishing the variant result in more severe Covid-19.
The claim that B.1.1.7 is more transmissible is based on primarily epidemiological evidence and data on increased viral loads, and is compelling but far from decisive. To demonstrate conclusively that B.1.1.7 is more transmissible, that needs to be quantified experimentally in animal models of Sars-CoV-2 transmission. Even if B.1.1.7 does prove to be more transmissible, it is not likely to be transmitted in a different way from all the other circulating Sars-CoV-2 variants. It has not acquired viral superpowers that render existing precautions irrelevant, and it is still transmitted primarily through inhaling or having direct contact with infectious respiratory aerosols and droplets.
#Covid-19#migrant#migration#angleterre#frontiere#sante#test#mutation##transmission#circulation