Looker, who spoke exclusively to The Age ahead of a media event, said while thunderstorm asthma events were still rare, Melbourne’s geography meant large doses of this allergen could be delivered efficiently.

Associate Professor Matthew Conron was called in to help treat about 200 patients who arrived at Melbourne’s St Vincent’s Hospital on the evening of the thunderstorm asthma event on November 21, 2016. The hospital was forced to declare an external disaster and set up an emergency clinic.

About 35 patients had to be admitted to the hospital, and one died.

Conron, the hospital’s director of respiratory and sleep medicine, said the patients were typically young and very unwell. They had either had mild asthma in the past or had never been diagnosed with the condition.

This assessment was backed up by a later study of 1435 patients who turned up at Melbourne hospitals during the thunderstorm asthma event. The study found more than half had never had an asthma diagnosis before their thunderstorm asthma episode.

About half of the patients told researchers they had never had asthma symptoms, yet when these same patients were asked if they had experienced shortness of breath, chest tightening and wheezing, 46 per cent of them had.

This was suggestive of underlying asthma, said Associate Professor Eve Denton, a respiratory and sleep physician at St Vincent’s and Alfred hospitals Melbourne.

“They were people who really had no history of asthma and [yet] were so bad on that night that they had to present to emergency.”

Denton said people might not realise that it’s possible to have asthma that occurs only in spring, a phenomenon she said was particularly common in Melbourne.

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“We do have patients in our clinic where if we measure their lung function outside of spring, it’s completely normal. And if we measure their lung function in spring, particularly on those really high pollen count days that tend to occur in November, then we can find on their lung function that they have demonstrable [confirmed] asthma.”

The specialist doctors are urging people experiencing symptoms including chest tightness, shortness of breath and wheezing to consult their GP.

Looker said Victorians could access thunderstorm asthma forecasts through the VicEmergency app.

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