Are we prepared for Thunderstorm Asthma?


The condition thought to be triggered by a combination of high grass pollen levels and a certain type of thunderstorm, results in large numbers of people developing asthma symptoms over a short period of time. In 2016, 8,500 in Melbourne were hospitalised as a result of it. Time for an action plan

On 21 November 2016, Melbourne witnessed an extraordinary increase in the number of asthma patients presenting to hospitals. The emergency services were not prepared for what was termed ‘Thunderstorm Asthma’. Ten people died as a result of this, 8,500 were hospitalised and many thousands were affected with respiratory problems. Hospitals were overloaded with thunderstorm asthma patients, thought to have been caused by rye grass pollen sweeping across the city during a dramatic cool change. The pollen burst into very fine particles, sparking asthma-like symptoms in thousands of people across the city.

Sources say Emergency Services Telecommunications Authority (ETSA) had received the maximum numbers of calls ever for a single problem, from 6pm on Monday 21 November to 6am the following day. At its peak, between 7pm and 7:15pm, the service received 201 calls. It had anticipated 29 calls. The event put such a strain on services in Melbourne’s west that no ambulances were available there within half an hour of the “surge” beginning.

The ten who died had been diagnosed with asthma at some point before the event, but several victims were notably affected when they went outside. The victims were mostly men, with an average age of 36, and were predominantly from Asian backgrounds who had recently immigrated to Australia.

It is hypothesised that they seemed to have developed allergies within three or four years of arriving Australia. Eight of the victims were from Melbourne’s north-west, where the storm might have hit hardest, but that socio-economic conditions and access to treatment might have been a factor.

A drastic change in weather conditions filled the environment with huge amounts of pollen and triggered massive asthma attacks and allergies in people all over the state. The problem was so severe that the emergency services struggled to cope with the demand of care. Since then, another mild episode of thunderstorm asthma has occurred again in Melbourne

New Thunderstorm Asthma forecasting system

A new world-leading thunderstorm asthma monitoring, prediction and alert system is now up and running, giving Victorians an early warning of possible epidemic thunderstorm asthma events this pollen season.

Marking the start of pollen season, the new thunderstorm asthma forecasting system will better predict and respond to large-scale emergencies such as thunderstorm asthma.

Not every thunderstorm causes thunderstorm asthma. The new forecasting system will predict epidemic thunderstorm asthma which is triggered by high grass pollen levels and a certain type of thunderstorm.

The forecasting system considers grass pollen forecasts, weather observations and data including wind changes, temperature, rainfall and grass coverage. It will then identify the risk of epidemic thunderstorm asthma using a traffic light scale of: green for low, orange for moderate, and red for high—and trigger warnings if required.

The forecasting system will run from 1 October until the end of December, the typical Victorian grass pollen season. To access the forecasts, Victorians should download the VicEmergency App or visit

But let’s understand thunderstorm asthma first to prepare ourselves for the coming spring and summer.

What is thunderstorm asthma?

Thunderstorm asthma is different from a regular asthmatic condition. Asthma attacks usually peak in winter season, generally triggered by recurrent viral infections, which cause muscles around small airways to squeeze tight, swell and create more mucus. This causes tightness in chest, cough and breathing difficulties.

Asthma and hay fever symptoms increase every year during grass pollen season. There is also the chance of an epidemic thunderstorm asthma event.

Thunderstorm asthma events are thought to be triggered by an uncommon combination of high grass pollen levels and a certain type of thunderstorm, resulting in large numbers of people developing asthma symptoms over a short period of time. These events not only cause a large number of people to become unwell but their sudden onset and potentially severe nature can put a strain on health services, with many people requiring medical support.

Thunderstorm asthma is uncommon, and the exact mechanism driving it is still unclear. One view is that pollen grains from grasses get swept up in the wind and carried for long distances. Some can burst open and release tiny particles that are concentrated in the wind just before the thunderstorm. These particles are small enough to be breathed deep into the lungs and can trigger asthma symptoms, making it difficult to breathe.

It is thought that the grass pollen grains and allergens are removed from the air by the rain from the thunderstorm.

Whole grass pollen grains are relatively large and can in some susceptible people cause irritation of the eyes, nose and throat, resulting in what is commonly known as hay fever.

On the other hand, the allergens released from burst grass pollen grains are small enough to get past the nose and throat and be breathed deeply into the lungs. Irritation here can trigger asthma symptoms such as wheezing, breathlessness, a tight feeling in the chest; or coughing.

Research to better understand how thunderstorm asthma events occur is currently underway.

When is thunderstorm asthma likely to occur?

Thunderstorm asthma events don’t occur every year but when they do, they can happen during the grass pollen season in south-east Australia.

The grass pollen season varies across Australia however in Melbourne it is typically from October through December.

Who is at risk of thunderstorm asthma?

Those at increased risk of thunderstorm asthma include: People with asthma, a past history of asthma, those with undiagnosed asthma (i.e. people who have asthma symptoms but have not yet been diagnosed with asthma), and those with seasonal hay fever (who may or may not have asthma). People with hay fever in south eastern Australia are likely to be allergic to grass pollen, and are therefore at increased risk of epidemic thunderstorm asthma.

What can you do to be prepared?

While the environmental conditions that have resulted in previous thunderstorm asthma events are uncommon, they will reoccur in the coming years and it is important that everyone is prepared. First, understand the phenomenon, and prepare an asthma action plan (where advised by your doctor) and /or have practical knowledge of the 4 steps of asthma first aid.

Have reliever medication appropriately available in grass pollen season and be aware of how to use it (ideally with a spacer), be alert to and act on the development of asthma symptoms as explained in your asthma action plan if you have one, or if you don’t, use asthma first aid. Be aware of thunderstorm forecasts particularly on high pollen count days.

For those at risk, where possible it’s best to avoid being outside during thunderstorms during the grass pollen season—especially in the wind gusts that come before the storm. Go inside and close your doors and windows and if you have your air conditioner on, turn it to recirculate.

Never ignore asthma symptoms like breathlessness, wheezing and tightness in the chest.

Start Asthma First Aid immediately and call Triple Zero (000) for help if symptoms do not get any better or if they start to get worse.

If you think you might have symptoms of asthma or hay fever, or if you experience wheezing or coughing with your hay fever, see your doctor to get symptoms checked and get a proper diagnosis. Around 1 in 4 people with hay fever also have asthma, and it is important to recognise that pollen can trigger asthma as well as hay fever symptoms. People with hay fever who also develop symptoms such as wheeze, shortness of breath and chest tightness should see their doctor. In an emergency, always call Triple Zero (000).

Many people have reservations regarding the use of Prednisolone- steroid. There is nothing to fear and people should consult their doctor and take the medication for three to five days—oral—to avoid admission in the hospital. In severe cases of thunderstorm asthma, Prednisolone can be lifesaving.

How can we monitor small children during this time?

With small children, it is important to keep an eye on their breathing. The tell signs could be that a child who usually does not wake up during the night is waking up often due to discomfort or is coughing during the night which is unusual for them. It indicates that the child is having breathing difficulties.

Also, if parents can hear a child breathe, it is a sign that they are having problems breathing. Another sign is if the child’s mouth turns blue or if they are lethargic during the day and not their usual active self. It is suggested that parents place their hand over the child’s stomach and count how many times the stomach goes up and down in a minute. For a small child (under 1 year of age), if the count is more than 60 per minute and for kids over 1 year of age the count is over 40 per minute, then it is an indication that the child is breathing faster than normal and needs immediate medical attention.

The writer is Director, Western Specialist Centre. Special thanks to Asthma Australia, SBS, Allergy Australia and emergency services.


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