Coronavirus, Covid 19: Why are new strains so dangerous and how we can stop them

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With the new, the most contagious Covid-19 alternatives It has been detected all over the world, and at the New Zealand border, the risk of further Level 3 or 4 lockdowns if those viruses enter the community increases.

These include a variable called B 1.1.1.7 Which has spread very quickly within the UK, and other new variants are now observed in South Africa And the Brazil.

Changes in the genetic code of viruses like Covid-19 happen all the time, but most of these mutations have no effect on how the disease spreads or how severe it is.

These changes could be useful because they leave an imprint in the virus’s genetic code that allows us to track how the virus spreads from person to person.

But the new variant discovered in the UK is More portability From the original virus that was prevalent in 2020. This means that it spreads more easily from person to person.

The good news is It does not cause a more serious disease Or it has a higher mortality rate than the original variant. Evidence suggests so far The vaccines will still be effective Against it.

The bad news, however, is that because it spreads more easily, it can potentially infect many more people, causing more hospitalizations and deaths as a result.

Why are easy-spread variants more dangerous

The average number of people infected with Covid-19 who transmit the virus to – the so-called R number – is 40-70 percent higher with B.1.1.7 than the original variant.

As the graph below shows, the mathematics of exponential growth means that even a small increase in the transmission rate worsens over time, rapidly resulting in an exponential growth in the number of cases.

A variant such as B.1.1.7 with a higher transmission rate is actually more dangerous than a variant with a higher mortality.

An increase in the death rate by 50 percent would definitely lead to an increase in mortality of 50 percent. But due to the exponential growth, shown in the graph, a 50 percent increase in transmissibility leads to a 25-fold increase in cases in just two months if left unchecked.

This would lead to 25 times more deaths than the original death rate.

How do we know that the new variable is more transmissible?

the number of Cases B.1.1.7 The variable increased rapidly compared to the original variant.

This could happen for a number of reasons. The new variant may simply be present in a part of a country or a group of people who are spreading the virus more quickly for another reason.

It can become immunosuppressed, which means it can re-infect people already infected with Covid-19 more easily. Or, it might cause people to become infected more quickly.

The researchers used the UK Mathematical models To test these hypotheses.

They found that the most appropriate explanation for the data is that the new variable is actually more transmissible. They estimated that a person infected with the new variant affected 56 percent more people on average than a person with the original variant.

Contacts tracking data From the UK it also showed that someone’s more close contacts with the new variant had been infected.

Patients with the new variant were also found More virus. Together, this provides strong evidence that the B.1.1.7 variant is between 40 percent and 70 percent more transmissible than the original variant.

The variants are found in South Africa and Brazil Share some of the same mutations As a variable B.1.1.7. There is some evidence for that It may also be more transmissible Or more capable of it Evading immunity.

But there is more uncertainty about these variables, partly because the data quality is not as high as it is in the UK. Very good at doing genome sequencing.

What does this mean for New Zealand border controls?

New variants were discovered in Many countries, Including persons in Managed isolation facilities in New Zealand.

There were previously several cases People who work in these facilities are catching the infection New arrivals.

The more transmissible variants reaching New Zealand borders increase the risks to these workers, who in turn have a higher chance of transmitting the virus to others in the community, thus increasing the risk of an outbreak in society.

In response, the government says international arrivals will need to test a negative within 72 hours before departure. They will also be required to take an arrival day test upon arrival in New Zealand.

Availability of these measures Extra layer In our defenses against Covid-19.

How can we manage risks?

The new variants propagate in the same way as the original version: through close interpersonal communication, especially in Crowded or poorly ventilated environments.

This means that all the tools we developed to fight the virus will still work. These include tests, contact tracking, masks, and physical distancing.

But whichever variable is more transferable has a higher R number. To control the outbreak, we need to bring the R to less than 1 and so we may need to use more of these tools to achieve this.

For example, in The Auckland outbreak In August 2020, alert level 3 was sufficient to contain the outbreak and ultimately eliminate it. Our analysis Alert Level 3 showed a reduction of R to about 0.7.

If we had a similar outbreak with the new variant, the R could be 50 percent higher which means it is higher than 1. In other words, we will likely need to use Alert Level 4 to contain the outbreak, and it may take longer to eliminate the virus than it used to be. In the previous.

To give our contact tracing tools the best possible chance of containing a new outbreak without alert level 3 or 4, we all need to do our part. That means searching for QR codes on exit and using the app to scan them as well

Stay home and get tested if you feel sick.

• Michael Planck is Professor of Applied Mathematics at the University of Canterbury. Shawn Hendy is Professor of Physics at the University of Auckland.

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