Kia ora. I'm one of the doctors at the Emergency Department.

I also now work in intensive care. I've provided medical cover at Nelson Mountain Bike Club events for the last seven years.

How we comply with this lockdown is crucial. Unchecked, this virus doubles in the community every three to four days. That means worst case scenario with no lockdown, from 20 cases in the Nelson region, we would have 10,240 cases in four weeks.

That means 1024 cases in hospital and 256 cases requiring intensive care. We have seven intensive care beds in Nelson and can possibly make three or four more.

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In a perfect lockdown, there is no more transmission. We likely have five or 10 times the reported cases in the community (based on modelling from other countries).

MARTIN DE RUYTER Dr Tom Jerram works in the emergency department and the intensive care unit at Nelson Hospital.

Which means maybe 200 cases in our region. That's 20 hospital admissions and five cases in intensive care.

We will not have a perfect lockdown, but the closer we get to it, the closer we get to the second scenario.

You can spread coronavirus when you have no symptoms. It can live on surfaces you touch for up to two days. Every social interaction is a chance for the virus to spread.

There are two problems with mountainbiking.

1. You may hurt yourself, despite riding within your ability. As a mediocre mountainbiker with three sets of broken ribs, two broken hands, a concussion, and untold cuts and bruises in the last 10 years in Nelson, I am only too aware of this.

I always thought I was riding "within my ability", we all do. If you hurt yourself, you break your social bubble, and expose yourself and others to danger.

Even coming to the Medical and Injury Centre or Emergency Department puts you and others at risk, and a rescue or ambulance is worse.

We may not have the hospital capacity to treat you and we want to reserve all our capacity for fighting this illness

Virginia Woolf Dr Tom Jerram says there are two problems with mountainbiking - you may injure yourself and need rescuing. There are plenty of surfaces like gates and benches that can transfer the virus.

2. Breaks in social distancing. Codgers Moutainbike Park is full of gates, benches and other surfaces just begging to transfer coronavirus.

The gate at the start of Sharlands trails, in the Maitai Valley, we all climb over is basically the perfect viral transfer spot.

I went up to Codgers a week ago and saw multiple people using benches and using their hands on gates.

It's much harder to be completely handsfree with a bike than on foot.

We all do need to get out for fresh air and exercise every day. Do it on foot, and alone. If we don't follow the rules, we will end up having this privilege taken away.

I know this is hard. We have all had to adjust rapidly to a monumental change in our lives. But what we do now will determine whether the next 12 months is manageable for us.

Kia kaha,

Tom