Thunderstorm asthma in Australia

How to identify those most at risk 

National Asthma Council Australia 

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Thunderstorm asthma can be life-threatening. Primary health care nurses play an important role in identifying people at risk of thunderstorm asthma, providing education about the risks and helping to ensure good asthma management. This includes educating people who live in at-risk areas as well as those who may be travelling over the holidays. 

What is thunderstorm asthma? 

Thunderstorm asthma is a potent mix of pollens, weather conditions and rain that can trigger severe asthma symptoms. 

In regions with seasonal high concentrations of airborne grass pollen, thunderstorms in spring or early summer (October to December) can trigger asthma in people with grass pollen allergy, even if they have not had asthma before. 

Who is at risk? 

The main risk factor is seasonal allergic rhinitis (hay fever) with or without known asthma.^1–4 Those who are strongly allergic to ryegrass pollen are at highest risk.²  

People with asthma who are allergic to ryegrass pollen and are not using inhaled corticosteroids (ICSs) are at highest risk of death or admission to an intensive care unit. The combination of asthma and grass pollen allergy increases the risk of life-threatening asthma requiring intensive care admission.^5,6 Poorly controlled asthma is associated with the worst outcomes. Treatment with an asthma preventer that contains ICSs appears to be protective.^3,4 Patients may present with asthma symptoms soon after exposure, or in the days following an asthma flare-up that they may have been trying to manage on their own. 

Preventing thunderstorm asthma 

Identify people with asthma and seasonal allergic rhinitis who live in or visit regions with high grass pollen levels. 

In patients with springtime allergic rhinitis (with or without asthma) 

Advise patients to: 

• check for alerts about high airborne pollen counts during spring (e.g., Melbourne Pollen, which has pollen count locations around Australia) 

• check thunderstorm asthma forecasts 

• avoid being outdoors just before and during thunderstorms in spring and early summer, especially during wind gusts that precede the rain front. 

Educate people without asthma to recognise and report possible asthma symptoms (wheeze, tight chest, dyspnoea) and to know how to access a rapid-acting reliever inhaler if needed. 

Patients with asthma 

• Patients with asthma should be prescribed an ICS-based preventer treatment as indicated. Most adults and some children with asthma should use ICS-containing preventer treatment. 

• Those allergic to grass pollens who are not already using ICSs, should be prescribed preventive ICS-based treatment in springtime. They need to start at least 2 weeks before exposure to springtime high pollen concentrations and thunderstorms and continue throughout the grass pollen season. 

• Ensure that patients have an up-to-date asthma action plan and that they always have access to rapid-acting bronchodilator relievers. 

• Encourage patients to have regular asthma reviews with their doctor. 

• Make sure patients carry a reliever inhaler (salbutamol or ICS-formoterol), know how to use it and replace it before the expiry date or when nearly empty.  

• Check and demonstrate correct inhaler technique each year before pollen season. Instructional videos on device technique are available from National Asthma Council Australia.  

• Provide the patient with asthma first aid education and explain when to call an ambulance.  

• Inform the patient that wearing a P2, P3 or N95 filtering mask may help reduce exposure to pollen allergens⁷ but should not replace avoidance.  

 
 

 

 

 

 

 

 

 

Figure 1: How thunderstorms increase grass pollen exposure 

Treating thunderstorm asthma 

When managing flare-ups in adults, children aged 6 years and over and children 1–5 years, follow the National Asthma Council Australian Asthma Handbook recommendations.8 

For the management of acute asthma in clinical settings, follow Australian Asthma Handbook guidelines8: 

1. Assess severity (mild/moderate, severe or life-threatening) while starting salbutamol treatment immediately: 

• adults and children over 6 years: 4–12 puffs (100 mcg per actuation) via pressurised metered-dose inhaler plus spacer for mild/moderate acute asthma; 12 puffs for severe acute asthma – doses repeated every 20 minutes for first hour; 2 × 5-mg nebules via oxygen-driven nebuliser for life-threatening asthma 

• children under 5 years: up to 6 puffs for mild/moderate or severe acute asthma via pressurised metered-dose inhaler plus spacer (with mask if needed) – doses repeated every 20 minutes for first hour; 2 × 2.5-mg nebules via oxygen-driven nebuliser for life-threatening asthma. 

2. Give supplemental oxygen therapy, if required, and titrate oxygen saturation to target of 92–95% (adults) or at least 95% (children). 

3. Monitor the patient’s response to bronchodilator therapy and repeat as required. 

4. Administer systemic corticosteroids within the first hour of treatment (routinely in adults and children 6 years and over; if there is an inadequate response to salbutamol in children under 5 years). 

5. Repeatedly reassess response to treatment and either continue treatment or add on treatments as indicated until acute asthma has resolved (or patient is transferred to an intensive care unit or admitted to hospital). Observe the patient for at least one hour after dyspnoea/respiratory distress has resolved. 

After the acute episode has resolved, comprehensive post-acute care should be provided to the patient and an appointment should be made for a thorough follow-up with their GP. 

Epidemic thunderstorm asthma  

Thunderstorm asthma epidemics can occur when a storm triggers asthma in many individuals with grass pollen allergy, resulting in a very high demand on ambulance and health services. Epidemic thunderstorm asthma events are uncommon but occur approximately every 5 to 7 years in Victoria and in some regions in rural New South Wales. 

In people with an allergy to grass pollens, thunderstorm asthma can be triggered by exposure to a high concentration of pollen fragments in wind gusts just before a thunderstorm (Fig. 1).  

In Australia, this mainly occurs in springtime or early summer in the south-eastern mainland and is associated with high perennial ryegrass (Lolium perenne) pollen counts.¹  

Grass pollen grains are drawn upwards into storm clouds. Some grains rupture and release many small pollen fragments. These fragments are blown down to ground level on the downdrafts and dispersed across the landscape in wind gusts that precede a storm.9 Small pollen grain particles that are inhaled into the lungs can trigger bronchoconstriction in allergic individuals, even if they do not have a diagnosis of asthma. 
 

The 2016 Melbourne thunderstorm asthma event  

What happened  

The world’s largest and most catastrophic epidemic thunderstorm asthma event occurred in Melbourne and Geelong in November 2016, on a day of extremely high airborne grass pollen concentrations.^3,6 It resulted in a sudden large surge in emergency ambulance calls, thousands of emergency department presentations and hundreds of hospital admissions.³ There were 35 intensive care admissions, an almost 10-fold increase in asthma-related hospital admissions and a more than sixfold increase in respiratory-related presentations to emergency departments, compared with the previous ³ years.⁶ Thunderstorm asthma contributed to 10 deaths, including five in people admitted to an intensive care unit.⁶  

Most patients presenting to health services with thunderstorm asthma did not have a prior diagnosis of asthma6 but almost all had seasonal allergic rhinitis and, where tested, very strong sensitisation to ryegrass pollen.2,6 All patients who were admitted to an intensive care unit or died had current doctor-diagnosed asthma and most were not using an ICS preventer.⁶  

What we learned  

The most important risk factors for thunderstorm asthma were strong allergy to ryegrass pollen and, among patients with asthma, a lack of ICS treatment.⁶  

Other possible risk factors included:  

• Asian ethnic background – a high proportion of people who presented to emergency departments with respiratory symptoms or were hospitalised with asthma were born in Sri Lanka, India or south-east Asia.⁶ 

• Age – the mean age of people presenting to emergency departments with respiratory symptoms was 32 years and worst outcomes were among adults.^3,6 

To find out more information about thunderstorm asthma and the National Asthma Council Australia, access the digital version of this article by scanning this QR code.   

 

 

 

 

National Asthma Council Australia 

The National Asthma Council Australia is a collaboration of four member organisations (APNA, Australasian Society of Clinical Immunology and Allergy, Pharmaceutical Society of Australia and Royal Australian College of General Practitioners) and the national trusted authority for asthma knowledge. We set and disseminate the standards for asthma care through our responsive and evidence-based asthma guidelines – the Australian Asthma Handbook – as well as resources for primary health care professionals. Our Sensitive Choice program empowers consumers to identify asthma and allergy-aware products and services. 

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