Thunderstorm Asthma: a storm on the horizon?
24th November 2021 - 0 comments
The clouds roll over, the winds pick up, and the air starts to feel dense. Shortly after you hear the deep rumble of thunder and a violent burst of lightning flashes across your eyes. Thunderstorms can be so dramatic that they take your breath away.
But what if they did actually take your breath away? Epidemic thunderstorm asthma (ETSA) can turn a primitive delight into a living, breathing nightmare… well, a ‘non-breathing’ nightmare to be exact.
Thunderstorm asthma is the triggering of an asthma attack by environmental conditions directly caused by a thunderstorm. In the last four decades, outbreaks – known as ETSA – have been reported globally. And ETSA may become more commonplace, with climate change potentially extending pollen seasons worldwide, as well as increasing the unpredictability and severity of weather events.
It never rains, it pours
Following the first report of ETSA in Birmingham, UK in 1983, a total of 23 episodes have been documented1. Australia has been particularly hard hit, reporting nearly half of the international episodes – and culminating in a catastrophic event in Melbourne in 2016.
The Melbourne event resulted in thousands of hospitalisations and an admission rate that rose by nearly 1000%1, completely overwhelming the healthcare system. Sadly, this ‘imperfect storm’ resulted in the death of ten patients. It begs the question, how exactly did a thunderstorm cause such massive consequences?
As wrong as rain
ETSA events largely coincide with peak pollen seasons where strong winds sweep high concentrations of aeroallergens towards unsuspecting populations. The major aeroallergen culprit in Australia is rye grass pollen grains – but these are generally too large to reach the depth of the lungs where an asthma attack is initiated.
Previously, scientists thought that rain droplets in clouds were to blame. The story goes that after cold air whips up grass pollen grains from below, they reach the storm clouds where water saturation causes them to burst.2 The resulting sub-pollen particles are small enough to easily penetrate deep within the lungs, turning a mild allergic reaction into something more deadly.
But the Melbourne storm of 2016 was accompanied by very little rain and humidity – so, is rain really to blame?
When lightning strikes
In April 2021, researchers released a paper offering an alternative theory3. Using data from the Melbourne 2016 event, they built models to test a range of potential pollen rupturing mechanisms.
Combined with laboratory experiments that subjected grass pollen to wind gusts, mechanical friction, humidity, and electrical pulses, the team were able to deduce that lightning strikes were likely among the worst pollen-smashing offenders.
Why is this important? If we can understand what causes pollen rupturing, we can use it to predict the timing of ETSA events – and in turn, prepare our healthcare systems and issue warnings to those most at risk.
While the authors conclude that none of the tested processes could be used as a reliable warning system just yet, it does offer an opportunity for future scope.
Chasing the rainbow with biologics
Although thunderstorm asthma currently accounts for very few of the overall cases, asthma in general is an extremely challenging and complex disease to treat. And, while current treatments are at the best they’ve ever been, difficult-to-treat asthma is still prevalent.
Biologics – pharmaceutical drug products produced from or using biological sources – have received considerable attention as an alternative treatment for asthma. Until recently, there were just five biologics approved for difficult to control asthma – namely omalizumab, mepolizumab, reslizumab, benralizumab, and dupilumab.
Very recently, AstraZeneca announced unprecedented results from trials of their severe asthma biologics treatment, tezepelumab. Following phase III trials the company announces that “it is the first and only biologic to consistently and significantly reduce asthma exacerbations in a broad population across Phase II and III clinical trials”.
Like the other treatments listed previously, tezepelumab is a human monoclonal antibody that blocks the production of a cytokine that plays a key role in asthma inflammation. Monoclonal antibodies are exciting and emerging therapies in a broad range of diseases – from cancer and autoimmune diseases to Alzheimer’s and even COVID-19.
Overall, the use of biologics have already shown a decrease in the frequency of asthma exacerbations – including reduced emergency room visits, hospitalisations, and the need for oral steroids4. And, with new and improved versions on the way, it is possible that a well-prepared health system could use these novel treatments when lightning next strikes.
To know which way the wind blows
As a result of climate change, future ETSA events are likely to become more common, more disastrous and more unpredictable – and therefore, preparation is key. As both modelling predictors of ETSA events and severe asthma treatments become more sophisticated, it is hopeful that we will be better prepared to weather any future storms.
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1. Price, D., Hughes, K. M., Thien, F. & Suphioglu, C. Epidemic Thunderstorm Asthma: Lessons Learned from the Storm Down-Under. J. Allergy Clin. Immunol. Pract. 9, 1510–1515 (2021).
2. PE, T. & H, J. Thunderstorm asthma. Curr. Allergy Asthma Rep. 4, 409–413 (2004).
3. Emmerson, K. M. et al. Atmospheric modelling of grass pollen rupturing mechanisms for thunderstorm asthma prediction. PLoS One 16, e0249488 (2021).
4. NHS Accelerated Access Collaborative » Asthma Biologics – Rapid Uptake Product. https://www.england.nhs.uk/aac/what-we-do/what-innovations-do-we-support/rapid-uptake-products/asthma-biologics/.