How New Zealand has managed to dodge the COVID-19 bullet again


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New Zealand has avoided community transmission, although an Australian visitor tested positive for the delta variant that dominates Australia’s latest COVID-19 outbreaks.

New Zealand health authorities reacted quickly, isolating and testing contacts and suspending travel. Of the 2,609 contacts of the traveler, 93% obtained a negative test result.

But considering that the delta variant depends on twice as infectious like the original strain, the unique nature of the spread of COVID-19 also explains in part why New Zealand has managed to prevent an outbreak.

Among the influencing factors , a variable is often overlooked: the K factor. This describes how a virus spreads in clusters and through superextension events, and we now know that it is a virus. important aspects of SARS-CoV-2, the virus that causes COVID-19.

We have become familiar with the numbers R: R0, which describes the number of people to whom an infected person will transmit the virus, on average, if not are in place, and Re describing the file assesses once public health measures such as masks, social distancing and vaccines have been introduced.

But soon studies and modeling of how COVID-19 spreads highlight the K factor, suggesting that only 10–20% of infected individuals account for 80–90% of the total number of cases. This implies that most infected people do not transmit the infection to other people.

Few people do most of the outreach

This pattern of propagation causes overexploitation events. It is very possible that the infected tourist belonged to 80-90% of the non-spreaders and did not transmit the infection to many other people. He himself may have been infected in an overexertion event in Australia.

New Zealand has successfully eliminated COVID-19 and has no known clusters, thanks to comprehensive border control and precautionary measures. This means that any new cluster or community drive chain would need multiple introductory wheels to get started.

You can think of it this way. If ten infectious people arrived in the country, it is likely that only one would spread the virus to levels that could surpass contact tracking.

This was shown in to study which used genomic data to track how the first wave of community transmission took place in New Zealand. The data not only confirmed the effectiveness of rapid public health interventions, but also highlighted the importance of factor K. “The effective reproductive number, Re, of New Zealand’s largest group decreased from 7 to 0.2 during the first week of blockade. Similarly, only 19% of the introduction of viruses into New Zealand resulted in the continuous transmission of more than one additional case. “

Vaccination and public health measures

Beyond these considerations, as the infected individual had already received a single dose of vaccine in Australia, it is possible that this would reduce the virulence of the infection.

It is also possible that some of the people you interacted with also received one or two doses of the vaccine. We cannot rule out a vaccination effect to keep the infection mild or even break the transmission chain.

What can New Zealand do to keep the delta variant at bay? The initial success of New Zealand’s elimination strategy helped restore the country to a situation where all new variants are imported rather than mutated from existing local infections. This is crucial as the mutation rate is higher during periods of uncontrolled spread. This did not happen in New Zealand.

Strict border control and quarantine of New Zealand, even in times of null community , helped keep the new variants in check.

Looking to the future, several issues will be critical. New Zealand must continue with border control measures to control infections abroad. We will have to negotiate travel bubbles based on the evolution of other countries.

I also support calls for accelerated deployment of vaccination and continued use of masks in public places and transportation. Last but not least, the use of the contact tracking app is critical here, as it helps to “reverse contact tracking” to quickly identify overlapping events.

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