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  • Writer's pictureTo Your Health Editorial Staff

Thunderstorm asthma season is on now

Michelle Griffiths remembers November 21, 2016 well.

It had been a windy, warm day in Melbourne, so that evening she and her husband opened up the big glass doors off their lounge room to air their house after the warmth of the day.

"I do remember being quite hayfevery and agitated in my sinuses," she says.

"I remember just getting very tight in my chest and wheezing."

Michelle had been diagnosed with mild asthma as a child, but aside from a little bit of exercise-induced asthma it hadn't bothered her much since.

That was until she got thunderstorm asthma during a previous Melbourne event in 2010. So when the winds started blowing that night in 2016 she knew something wasn't right.

"I knew at that point that I needed to shut the doors because we had all of the air blowing through the house, which is the worst thing you can do."

Luckily, Michelle had an asthma reliever on hand to treat her symptoms, but she still remembers feeling scared and obsessed with trying to get her airways clear.

She wasn't the only person affected that night.

A catastrophic event

Melbourne's 2016 thunderstorm asthma event was the largest and most devastating thunderstorm asthma event ever recorded worldwide, says Frank Thien, director of respiratory medicine at Eastern Health.

It resulted in over 3,500 emergency presentations, 35 ICU admissions and 10 deaths.

The majority of those affected were younger people.

"Of the people who turned up into our EDs in the thousands in 2016, the median age was 32," Professor Thien says.

Before that night, there had been one or two reports of deaths associated with thunderstorm asthma in the distant past, but never so many on one occasion, says Jo Douglass, a physician in allergy and clinical immunology at the University of Melbourne and the Royal Melbourne Hospital.

"One of the big risks about thunderstorm asthma is that for many people it's completely unexpected, and so they may not have awareness of or access to reliever treatment [the blue puffers] or an action plan to keep themselves safe," Professor Douglass says.

"In the 2016 event and perhaps in those similarly earlier — 2010 — emergency departments and emergency facilities were somewhat overwhelmed by the volume of asthma sufferers who presented."

About two-thirds of the people who went to hospital in 2016 didn't know they had asthma, but when questioned, a further half of those people reported previous asthma symptoms including shortness of breath, cough, wheeze and night waking with cough or wheeze.

The 2016 event taught us how severe thunderstorm asthma can be and that people's lives can be at risk, Professor Douglass says.

"I think it changed our perception of hay fever as being a benign but troublesome condition," she says.

"It has caused us to recognise the risk of hay fever and asthma when they are together, to try and remember people with asthma are at great risk of thunderstorm asthma.

"And to really encourage both prediction, so people can stay out of harm's way, and also preventative treatment, to keep people with asthma safe."

What causes thunderstorm asthma?

While Melbourne is well-known for the severity and regularity of its thunderstorm asthma events — they occur on average every five to seven years in the Victorian capital — they've been reported in other parts of Australia too, including Wagga Wagga and Sydney.

Grass pollen is usually the cause of thunderstorm asthma in Australia, Professor Douglass says. In other parts of the world, a range of pollens and even fungi can be the driver.

You usually get a thunderstorm asthma event after a few warm days of high pollen count and you then get a severe storm. But not every spring thunderstorm leads to thunderstorm asthma.

It's to do with a change in humidity and a drop in pressure.

Grass pollen gets sucked up into the storm as it's forming, and that's what then gets pushed down in the downdraft of the initial storm front and triggers most of the thunderstorm asthma.

When these pollen grains are exposed to a great rise in humidity, they burst and release the fragments inside them.

These fragments are small enough, at two to five microns, to be breathed right down to the bottom of the lungs.

"So the lungs are getting a dose of grass pollen allergen they wouldn't normally see because it's normally filtered out by the upper airway," Professor Douglass says.

The epidemic of asthma triggered by a thunderstorm asthma event occurs abruptly, she says.

The bulk of people present to hospital within a few hours of the event passing, but asthma presentations remain very high for the subsequent day.

"So there is both an early acute phase and also a later phase of asthma as well, which fits with what we know about the allergic response to grass pollens."

Long-term effects

Professor Thien and colleagues recently published a three-year longitudinal study, following up with people who were impacted by the 2016 Melbourne event.

It's the first study of its kind to follow patients for so long after a thunderstorm asthma event.

What they found is that there were a lot of patients who had very persistent asthma symptoms even three years after the event.

"It suggests that it's not just a one-off thing that you just get over after a few weeks," Professor Thien says.

So for people who have had thunderstorm asthma symptoms, this can be a trigger for worsening asthma overall, Professor Douglass says.

"It does suggest that there is something very important about this initial exposure that might actually be triggering asthma symptoms or airway hyperresponsiveness in people.

"Airway hyperresponsiveness is a cardinal feature of asthma, and I often describe it as the airway being twitchy, so super-sensitive, more sensitive than someone who doesn't have asthma to environmental triggers, things like allergens, but also things like cold air that will cause the airways to constrict."

The complication of COVID-19

Currently we're looking at this year being an average to slightly above average grass pollen season for Melbourne, says coordinator of the Melbourne Pollen Count, Ed Newbigin of the University of Melbourne.

"Our average would be about 20 of these high and extreme grass pollen days across the season [from October to December], now currently we're expecting around about 25," Dr Newbigin says.

Whereas, according to his colleagues in Sydney, they're having a bumper year, particularly as it's been a lot wetter further north.

"Sydney gets very few high and extreme days across their season," Dr Newbigin says.

"But they've already had quite a few already, and Canberra's the same."

This year we're also approaching the height of the hayfever season with the added burden of the coronavirus pandemic.

"I think the spectre of an overwhelming emergency presentation in the setting of a potential COIVD epidemic is particularly concerning because emergency department resources are somewhat stretched by COVID, and the necessity of managing people who are potentially infected," Professor Douglass says.

"That already is a drain on resources, and every emergency department in Victoria has been reconfigured to manage that risk.

"And so further overwhelming that with people with respiratory difficulties will make it even harder to manage a very big event."

What you can do to be ready for a future thunderstorm asthma event

There are three pieces of advice Professor Douglass would like people to follow this year, in case of an upcoming thunderstorm asthma event.

  1. If you have hay fever and asthma, recognise that you could be at risk of thunderstorm asthma. Speak to your doctor, have an asthma plan and reliever medication on hand so you know what to do if you have sudden asthma symptoms.

  2. Heed the thunderstorm asthma warnings available in your local area. For example, warnings are available in Victoria on the Melbourne Pollen and Vic Emergency apps. If a warning is in place, stay indoors at the time the thunderstorm is predicted.

  3. Manage your hay fever with antihistamines and nasal sprays to keep your symptoms under control. Some symptoms of COVID-19 and hay fever overlap, so by keeping your hay fever well-controlled there will be no risk of you confusing it with COVID-19.

Having reliever medication handy is advice Michelle Griffiths has taken to heart.

"I can't remember the last time that I have had to have some of my asthma pump," she says.

"But when it hits spring I am now very aware of it, and I do go and buy new Ventolin. Just having it around gives me peace of mind for those times just in case.

"We can't control the weather but you can have your asthma pump around."

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