New Zealand has one of the best healthcare systems in the world, but will be overrun if large numbers of people fall ill at the same time, writes Paul Young.

OPINION: I am an intensive care specialist. I work with a remarkable group of doctors and nurses and it's no exaggeration to say that, in the ICU, we do miraculous things.

We save lives.

The first day I ever worked in the ICU as a junior doctor I looked after someone in their 30s.

He had a cardiac arrest in the community. His heart stopped beating. He was resuscitated by his partner. He was brought to the hospital by ambulance in a coma.

He required life support in the ICU for 48 hours. He woke up, left the ICU, and recovered completely.

I have looked after many more patients just like this in the decade and a half that I have worked in the ICU. More than I can count.

Prime Minister Boris Johnson has announced that 405,000 people have signed up to be volunteers for the NHS during the coronavirus outbreak.

Patients from all areas of medicine and surgery can become critically ill, and when they do, they are referred to the ICU for care.

It's the kind of care that can't be provided anywhere else. Most of the patients we look after in the ICU would die without the life support they receive, and yet, more than 9 out of 10 survive.

If you require ICU care in New Zealand you are less likely to die than almost anywhere else in the world.

Indeed, I have been at international conferences where speakers have suggested, perhaps tongue in cheek, that the best thing to do if you are critically ill is get on a plane to New Zealand immediately. Our ICUs are so good, because we have highly skilled staff.

Covid-19 is an unprecedented threat to the health of New Zealanders and to our ability to properly staff our ICUs. We are working to provide some training to non-ICU hospital staff who can help us.

RICKY WILSON/STUFF Auckland's streets are deserted on the first morning of the coronavirus lockdown.

We have sourced additional machines (ventilators) to provide life support. We can expand the size of our ICUs to a degree.

We are preparing to do this. In doing so we will be balancing the level of care we are able to provide with the number of people requiring it.

We will always provide the best care we can but when the Prime Minister talks about the healthcare system being overwhelmed, the capacity of our ICUs is key.

An overwhelmed ICU means a healthcare system that can't provide care to our sickest patients.

It's not just about patients with Covid-19. It's about every sick patient in the hospital.

Covid-19 is a highly contagious disease. In February I posted on Twitter that the world would pass 100,000 cases in mid-March, with a million cases by early April, 100 million cases by the end of April, and a billion cases by the middle of the year.

At the moment we are running slightly ahead of schedule.

An uncontrolled epidemic in New Zealand could massively overwhelm the capacity of our ICUs.

While Covid-19 is a mild illness for the vast majority of people, a small number of people get sick enough to need hospital, and a small number of these people need ICU.

The problem is that, because Covid-19 is so contagious, an uncontrolled epidemic means lots of people getting the illness at the same time.

There could be more than ten times more patients needing intensive care than there are beds available.

The good news is that unlike many places in the world, we don't have an uncontrolled epidemic in New Zealand. Instead, we have a unique opportunity.

Never has there been a better time to be an island nation at the bottom of the world. Our Ministry of Health and our government have listened to the advice of experts.

They have done exactly what was needed and now, not only do I believe that we can control coronavirus in New Zealand, I believe that we might even be able to eliminate it region by region. This is what we should aspire to.

If we do this, many New Zealanders will gradually be able to go back to work while the country waits for a vaccine.

While there might be a billion cases of Covid-19 in the world by the middle of the year, our country could escape relatively unscathed.

If we don't follow the advice of our government and our public health officials, we will have an epidemic too and tens of thousands of people will die. It's that simple.

In the ICU, we are as prepared as we can be. We have done all we can do. What happens next is up to you.

Over the coming weeks and months my colleagues and I are going to be going to work to save lives, but we need you to stay home to do the same.

I promise you that if New Zealand pulls together as a community and stays at home dedicatedly sitting on the couch and watching TV, you will save more lives than I will in my entire career.

Dr Paul Young is an intensive care specialist based in Wellington with the Capital & Coast District Health Board. He can be found on Twitter @DogICUma