Ways to protect yourself from "Thunderstorm asthma"

Authorities in Victoria say the death toll from 21st November's freak thunderstorm asthma event in Melbourne has risen to eight. The storm saw more than 8500 people admitted to hospital with severe asthma. What causes the storm to affect people with breathing problems? How can such incidents be prevented? Melbourne General Practioner Bimal Shrestha had this to say.