With confirmation that the latest community transmission of Covid-19 is the Delta variant, let's get our heads around what that is and how it is different from the strain we fought last year.

It was confirmed today that the community case of Covid-19 and all six related cases in New Zealand are the Delta variant of the virus.

Delta is now the dominant variant of the virus in many parts of the world, making up 93.4 percent of cases in the United States during the last two weeks of July.

All 79 cases of Covid-19 in New Zealand isolation facilities from July 19 to August 9 have been the Delta variant. 

A variant is a mutated strain of a virus. There have been four confirmed variants of the Covid-19 virus since it appeared in late 2019 - Alpha, Beta, Gamma, and Delta.  

Delta has proven the most contagious version of the virus yet, and is potentially more harmful, and more resistant to vaccines.

The American Centre for Disease Control reports the Delta variant is more than twice as contagious as the original strain of Covid-19.

Those infected with the Delta strain are likely to experience the same symptoms as other strains, with a cough, fever and shortness of breath. However, reports have shown potentially higher cases of symptoms such as digestive issues, blood clots, and hearing loss.   

A Canadian study found those with Delta are twice as likely to need hospitalisation - with an 234 percent increase in admission to an intensive care unit, and a 132 percent increase in chance of death.

Vaccines may also be less effective against the Delta strain. While those vaccinated with two  doses of the Pfizer vaccine are 95 percent immune to the original strain, research has found it may only be 88 percent effective against the Delta strain.  

Delta is also more transmissible than other variants, even in vaccinated people. With previous variants, if a vaccinated person became infected, they hosted less of the virus in their body. However, the Delta variant reproduces similar levels in both vaccinated and unvaccinated people, although it appears vaccinated people recover more quickly.  

Delta, and other variations of Covid-19, were created by mutations.

As viruses reproduce, random mutations to their DNA occur, and there is a chance the next generation will have mutated. Most of the time these mutations have little impact, but occasionally they will make the virus more capable of spreading, doing harm to the people they infect, and possibly avoiding the defenses produced by immune systems and vaccinations.

The more times a virus replicates, the more chances of successful mutations occurring. 

And unfortunately, the Covid-19 virus has gotten a lot of opportunities to replicate - infecting 208 million people in just over a year and half. 

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