Sunday, 29th March, 2020:
A public health professor says the lockdown period is critical for people to change their behaviour and not share the Covid-19 virus.
Professor Michael Baker from Otago University and other health professionals urged the government to implement the level 4 lockdown to break the chain of transmission. It began at 11.59pm on Wednesday.
He told Morning Report the move was further allowing the country to build capacity to stamp out the virus, putting it on a "path of elimination", similar to the one taken by China.
"I know I had my best night's sleep on Wednesday. I was imagining all those unseen chains of transmission around New Zealand that we might have missed gradually getting snuffed out because people are no longer sharing the virus around," he said.
"It's so critical in this period that people change their behaviour and not share this virus."
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Flu viruses mutate over time causing small changes to proteins on their surface called antigens. If the immune system has met a particular strain of the virus before, it is likely to have some immunity; but if the antigens are new to the immune system, it will be weakened.The influenza A virus can mutate in two different ways; antigenic drift, in which existing antigens are subtly altered, and antigenic shift, in which two or more strains combine. Antigenic drift causes slight flu mutations year on year, from which humans have partial, but not complete, immunity. By contrast, the new strain of H1N1 appears to have originated via antigenic shift in Mexican pigsThe name "swine flu" is a slight misnomer as it is believed pigs acted as a mixing pot for several flu strains, containing genetic material from pigs, birds and humans. Most humans have never been exposed to some of the antigens involved in the new strain of flu, giving it the potential to cause a pandemic.The new virus has made the jump from pigs to humans and has demonstrated it can also pass from human to human. This is why it is demanding so much attention from health authorities. The virus passes from human to human like other types of flu, either through coughing, sneezing, or by touching infected surfaces, although little is known about how the virus acts on humans. 
Symptoms usually similar to seasonal flu - but deaths recorded in Mexico
It is a new version of the H1N1 strain which caused the 1918 flu pandemic
Too early to say whether it will lead to a pandemic
Current treatments do work, but there is no vaccine
Good personal hygiene, such as washing hands, covering nose when sneezing advisedFLU PANDEMICS1918: The Spanish flu pandemic remains the most devastating outbreak of modern times. Caused by a form of the H1N1 strain of flu, it is estimated that up to 40% of the world's population were infected, and more than 50 million people died, with young adults particularly badly affected1957: Asian flu killed two million people. Caused by a human form of the virus, H2N2, combining with a mutated strain found in wild ducks. The impact of the pandemic was minimised by rapid action by health authorities, who identified the virus, and made vaccine available speedily. The elderly were particularly vulnerable
