How contagious are the Covid-19 variants? Explain the dangers of a more communicable disease.

A more contagious SARS-CoV-2 virus is more deadly. Not because it gets sicker, but because it reaches more people. More illnesses means more cases: more mild cases, worse cases, more long-term complications, more hospitalizations and more deaths.

There is no perfect estimate for how much more contagious the SARS-CoV-2 variant called B.1.1.7, first discovered in the UK, may be. More careful laboratory work on animals needs to be done to nail it down, which can take a few more weeks. But preliminary estimates find it between 30 percent and 70 percent more contagious. This variant is now appearing all over the world: in the USA, throughout Europe, in Asia and elsewhere. This is of particular concern as the spread of the pandemic in the US and elsewhere continues to reach new heights.

There is also a variant called 501Y.V2 that was first found in South Africa; it appears less widespread than B.1.1.7, but also more contagious than older variants. It is still possible that other more transferable variants will appear in the future. Scientists just do not know.

No matter exactly how transmissible any new variant is, any possible increase in transmissibility is extremely worrying for epidemiologists and others in public health. This means that our collective and individual action to stop the spread is more critical than ever before.

Here are some important reasons why.

A more transmitted virus simply means more cases

The reason for concern about a more contagious variant of the virus is simple. ‘Once it [the variant] become widespread, it will significantly accelerate transmission, ”Harvard epidemiologist Marc Lipsitch said in a press release. Accelerated shipping means more cases.

This is because the virus grows exponentially. Each increase in inherent transferability increasingly causes a greater number of cases if the controls do not also accelerate to keep up.

With a 50 percent increase in contagion, “you get twice the number of cases in less than two weeks,” says Lipsitch. ‘And in a month or so you have four, five times as many cases. But it is very approximate. “It could be higher,” he says.

A more transmitted virus means we have to work harder to stop the spread

Epidemiologists think of the transmissibility of a virus with a figure called R, or the basic reproduction number. It describes how many new cases will follow on average one case of the virus.

At the beginning of the outbreak, before the world came into operation, epidemiologists estimated the R about 2 or 3.. R has been reduced in many states to about 1.1 to 1.2. But as long as the R digit is greater than 1, the virus can spread exponentially.

Suppose a community got its R-value down to 1. Then a 50 percent more transferable variant comes along. This could mean that the same mitigation attempt that dropped the old variant of the virus to 1 now only drops it to 1.5.

That is, to combat a more transmissible version of the virus, communities need even stricter control.

A virus that is 50 percent more transmissible, Lipsitch says, means’ we need to reduce our contacts by another third compared to the already strong restrictions [already in place] to get back to the same place we were. This could mean that businesses that are partially open, schools will be closed, and other such closure measures.

If communities do nothing based on a more contagious variant, the numbers can add up very quickly. Bill Hanage, another Harvard epidemiologist, guided me through the following thought experiment.

Suppose a community has the virus more or less under control. The R-value in the area is 1, which means that the number of cases in the area remains constant, month to month.

In this scenario, “you now have 1,000 cases and you will have 1,000 cases from now on,” says Hanage (his scenario assumes that it takes about five days before one infection causes the other). ‘Now imagine that the virus is 50 percent more transmissible. …. 1,000 cases of such a virus will now translate more than 10,000 cases per month if you do nothing! ‘

Christina Animashaun / Vox

A more contagious virus increases the number of people to be vaccinated

A more transmissible virus also raises the threshold for herd immunity, or a rough estimate of the percentage of people in a population who need to achieve immunity, ideally through a vaccination so that the outbreak can decrease in size.

Herd immunity thresholds depend on the value of R. The higher the R value, the higher the threshold. As a more communicable variant prevails around the world, it increases the pressure on vaccination campaigns to vaccinate even more people. Already, more than 70 percent of the population seems to be immune to herd immunity (although the exact figure needed is unknown). This is already a very high and difficult measure to clean, given the slow early spread of the vaccinations.

There is also the possibility that the virus may mutate into a form that reduces the effectiveness of current vaccines.

A more transmitted virus means more death

One good news about the B.1.1.7 variant: so far it does not look more deadly than older variants of the virus. That is: according to the early data, it is no longer likely that someone who gets it will end up in the hospital or die.

But more infections means more death. “In general, as more people become infected, the number of hospitalizations and deaths increases accordingly as part of the number,” says Emma Hodcroft, a molecular epidemiologist at the Institute of Social and Preventive Medicine in Switzerland. “So more cases are also bad news.”

A 50 percent more contagious virus is an even more deadly problem than one that is 50 percent more deadly, according to the London School of Hygiene & Tropical Medicine epidemiologist Adam Kucharski explains on Twitter.

If a city had an R-value of 1.1 and 10,000 people were infected within one month, you would expect there to be 129 deaths, he says.

Increase the virus lethality by 50 percent in that scenario and you would expect 193 deaths – an increase of 49.6 percent.

Increase the infectivity of the virus in this scenario by 50 percent and you get 978 deaths, Kucharski finds. This is an increase of 658 percent. This is a theoretical calculation, but the key point is the exponential effect, as Kucharski explains.

It is not entirely clear whether this will happen

Again, the estimate of 50 percent increased transferability is just an estimate. And even if new variants are more portable, it can be difficult to predict how much more portable it will be in different places.

Hanage emphasizes that the 50 per cent more transferable figure reported is based on how this variant performs in the UK. Elsewhere – with different social distance compliance, different mitigation measures in place – the new variant may behave differently. It’s complicated, yes, but it’s outbursts for you.

But even the hypothetical threat of a more communicable variant is a call to action.

To prevent more mutations from occurring, to prevent more problematic variants from occurring, the spread of SARS-CoV-2 should be halted in general. First, it helps us deal with the overall pandemic. But “it’s also comfortable how we get less emerging variants,” Angela Rasmussen, a virologist at Georgetown’s Center for Global Health Science and Security, told me in a December interview. ‘If the virus does not repeat, it can not change. And if it can not mutate, the new variants can not emerge. ”

The new variant means that our individual actions are more than ever before. This variant is distributed in the same way as other SARS-CoV-2 variants, and the same precautions apply. Social distance, mask wear and ventilation are just as important as ever.

With the new variant around, Lipsitch says, ‘Your isolation and detection of quarantine and contact is significantly more important, even more so than before. So you do more for the world. ‘

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