Over the past few weeks in Victoria and other parts of Australia, we’ve been seeing some wild and stormy weather.

And with those storms has come the risk of thunderstorm asthma.

An Australian ambulance with sirens on speeding down a street — Ambulance services and hospital emergency departments were overwhelmed by asthma cases. Picture: Shutterstock

You may remember back in 2016, when thousands of people in Victoria suddenly developed breathing difficulties.

More than 3,300 people overwhelmed ambulance services and hospital emergency departments with asthma – hundreds were admitted to hospital. Tragically, ten people died as a result.

That event is now recorded as the world’s largest and most catastrophic epidemic of thunderstorm asthma.

But it’s the response to this event that has shaped the warning systems we see today.

With the recent stormy weather across southeast Australia, those emergency warning systems have now issued multiple thunderstorm asthma alerts.

Sciences & Technology

Thunderstorm asthma: Counting pollen to save lives

The very worst day in an annual surge

The 2016 severe thunderstorm asthma event seemed to come as a surprise, but it shouldn’t have.

Thunderstorm asthma events have been reported about every seven years in Melbourne since 1984. With population increases, there are many more people living in the north and west of the city who are exposed to the particular weather conditions that cause thunderstorm asthma.

In Melbourne, thunderstorm asthma events happen when severe storm fronts travel across from the north and west of the city in the spring – and especially after a day or more of high grass pollen counts.

But not all storms cause thunderstorm asthma: so, there are probably additional weather factors that are worth exploring.

Now, in 2024, there is a Victoria-wide pollen reporting service and detailed meteorological monitoring for weather events that are likely to lead to asthma epidemics.

A mature women suffering from hay fever outdoors — Hay fever – or allergic rhinoconjunctivitis – affects one in five people in southeastern Australia. Picture: Getty Images

Pollen counts are now distributed throughout the state as an early warning for both city and rural dwellers who are exposed to high levels of grass pollen.

The warning system includes notifications through the Victorian Emergency Services website and the VicEmergency app, as well as websites and apps that report on pollen, like Air Health.

One of the important things we’ve learned about thunderstorm asthma is that as a single event, it is the very worst day in an annual surge in emergency asthma presentations over springtime.

If we look at information over 25 years of Victorian emergency department presentations for asthma, it shows us that there is a reliable seasonal surge of emergency asthma presentations in children and younger adults between October and December every year, usually, but not always, associated with thunderstorms.

So, the major thunderstorm asthma events are the worst days of this seasonal surge.

Sciences & Technology

Melbourne’s pollen riddle

A “trifecta of exposure”?

Springtime in Victoria is also grass pollen season.

And the data suggests that a grass pollen allergy is a major contributing factor to springtime asthma.

So, if we now know that seasonal asthma and thunderstorm asthma recur every springtime, what can we do to keep people safe from seasonal asthma flare ups?

Well, we already know that springtime asthma and thunderstorm asthma almost always occur in people who suffer from springtime hay fever.

Hay fever – or allergic rhinoconjunctivitis – is very common in southeastern Australia, affecting one in five people. Almost all hay fever sufferers in south-eastern Australia are allergic to ryegrass pollen, but our research tells us that the severity of hay fever does not correlate with thunderstorm asthma risk.

A concerned mother helping her young daughter take asthma medication — Our research focuses on identifying people at greater risk of seasonal and thunderstorm asthma. Picture: Getty Images

Some have said that the risk of thunderstorm asthma is a "trifecta of exposure" – the storm, hay fever and an allergy to ryegrass pollen.

But if this is true then nearly one in five in our community should have asthma treatment on hand during the springtime. This is unlikely.

Our research focuses on identifying people at greater risk of seasonal and thunderstorm asthma so that they can start appropriate treatment early.

We do know that people who have asthma and hay fever are at greatest risk of thunderstorm asthma, and they should definitely have preventer treatment during the springtime.

We also know that people who have Asian or Indian ancestry, especially those who were born in Australia, have a much higher risk of severe seasonal allergic asthma.

Sciences & Technology

The sticky business of pollen counting

Preventive and protective treatments

Crucially, nearly two thirds of the people who present in thunderstorm asthma events do not realise that they have asthma.

So, the question is, can we provide better evidence to identify people who have hay fever, who justify having asthma treatment?

Our research tells us that people who are very highly allergic to ryegrass pollen are at greater risk – and this might be something that could be used by doctors to prescribe asthma preventive therapy.

Local doctors are best placed to identify people with asthma and to prescribe suitable preventive and protective treatments for asthma during spring.

But, importantly, hay fever treatments like antihistamines, are unlikely to reduce the risk of asthma.

A lightning strike in Melbourne on a hot 44 degree day — Climate change in Australia is likely to lead to higher levels of more potent grass pollen. Picture: Getty Images

One of the easiest ways to keep people safe is timely public warnings and advice to keep people out of thunderstorms.

Most of the grass pollen that triggers thunderstorm asthma is right at the storm front. So, staying indoors with windows closed or limiting exposure to this first part of the storm would almost certainly protect many.

The final piece of the puzzle in allergic and thunderstorm asthma relates to climate change.

We’re already seeing changes in the season for grass pollen with an earlier beginning and longer season, along with more frequent and severe storms.

We know that climate change in Australia is likely to lead to higher levels of more potent grass pollen. So, the risks for people with seasonal and thunderstorm asthma are likely to increase.

It’s another important reason to make sure we have an effective alert system for thunderstorm asthma alongside a robust medical approach to identify and treat that risk.

This article was first published on Pursuit. Read the original article.

Dr

Rachel Tham

Senior Research Fellow

Department of Medicine

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