About epidemic thunderstorm asthma
What is epidemic thunderstorm asthma?
Grass pollen season brings a seasonal increase in asthma and hay fever. It also brings the chance of thunderstorm asthma. When a large number of people develop asthma symptoms over a short period of time, caused by high amounts of grass pollen and a certain type of thunderstorm, it is known as epidemic thunderstorm asthma.
Melbourne experienced the world’s largest epidemic thunderstorm asthma event on 21 November 2016, with thousands of people developing breathing difficulties in a very short period of time.
Epidemic thunderstorm asthma is thought to be triggered by a unique combination of high grass pollen levels and a certain type of thunderstorm with strong winds. Grass pollen grains 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 gusts that come just before a thunderstorm. These particles are small enough to be breathed deep into the lungs and can rapidly trigger asthma symptoms, making it difficult to breathe.
This can become very severe, very quickly and many people may require medical help at the same time.
Thunderstorm asthma can affect those with or – especially people who experience wheezing, breathlessness, a feeling of tightness in the chest or coughing with their hay fever. That’s why it’s important for people with asthma or hay fever to know about thunderstorm asthma and what they can do to help protect themselves during grass pollen season.
Is there a risk of epidemic thunderstorm asthma every time there is a thunderstorm?
No. Epidemic thunderstorm asthma events are uncommon and don’t occur every year. Epidemic thunderstorm asthma events are thought to be triggered by a unique combination of high grass pollen levels and a certain type of thunderstorm with strong winds (rather than all thunderstorms). Rye grass pollen levels are thought to be an essential factor in determining whether an epidemic thunderstorm asthma event may occur. In Victoria, the pollen season is typically from the beginning of October to the end of December.
Who is most at risk of thunderstorm asthma?
Those at increased risk of thunderstorm asthma include:
- people with asthma
- people with undiagnosed asthma (i.e. people who have asthma symptoms (such as wheezing, breathlessness, a feeling of tightness in the chest or a persistent cough) but have not yet been diagnosed with asthma)
- those who have had asthma in the past
- people with hay fever (seasonal allergic rhinitis) who may or may not have asthma.
People with hay fever in south east Australia are likely to be allergic to grass pollen and are therefore at increased risk of epidemic thunderstorm asthma. Having both asthma and hay fever or poorly controlled asthma increases the risk further.
Have there been other epidemic thunderstorm asthma events?
Epidemic thunderstorm asthma events are uncommon and don’t occur every year, but when they do, they can happen during the Victorian grass pollen season.
Melbourne experienced the world’s largest epidemic thunderstorm asthma event on 21 November 2016, with thousands of people developing breathing difficulties and requiring emergency department attention, and hundreds of people requiring hospital admission in a very short period of time.
Although there have been other epidemic thunderstorm asthma events previously reported in Melbourne, none have been close to the size and severity of the November 2016 event. Five other epidemic thunderstorm asthma events in Melbourne have been recorded in medical literature since 1980.
While there are still many unknowns about the exact mechanism causing epidemic thunderstorm asthma events, we do know that in 2016 many people who were affected were unaware of the risk to their health and of the steps to take to protect themselves and those in their care.
About preventing and treating epidemic thunderstorm asthma
What should everyone do?
Epidemic thunderstorm asthma events are uncommon and don’t occur every year. However, people should be aware of the heightened risk of thunderstorm asthma in general throughout the grass pollen season and be appropriately prepared. It’s important for everyone in south-east Australia to know about epidemic thunderstorm asthma and what they can do to help protect themselves if an event does occur.
What should everyone at increased risk of epidemic thunderstorm asthma do?
There are some key actions everyone at increased risk can take:
- Learn about epidemic thunderstorm asthma and what you can do to help protect yourself during grass pollen season.
- Where possible, avoid being outside during thunderstorms from October through December – 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.
- Have an up-to-date asthma action plan or hay fever treatment plan and know the four steps of asthma first aid.
- Have reliever medication available in grass pollen season and know 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.
- Check the epidemic thunderstorm asthma risk forecast during the grass pollen season on the to see if there is an increased chance of an epidemic thunderstorm asthma event occurring.
Note that the risk forecast should not replace appropriate prevention and good asthma and hay fever management, which is the best way to protect yourself from thunderstorm asthma.
The forecasting system is also not designed to forecast the risk of individuals suffering asthma and hay fever symptoms, which can occur every year during the grass pollen season.
How can I prevent thunderstorm asthma if I have asthma?
- If you currently have asthma, make sure you have regular reviews with your GP about your asthma to ensure that you have the right and that you have good control of your asthma.
- It is also important that you have an up-to-date asthma action plan and that you see your GP to ensure that it includes advice for thunderstorm asthma.
- Always carry your reliever medication with you – this is your emergency asthma first aid medication should you need it.
If you also have hay fever, make sure it is treated adequately. Speak with your pharmacist or doctor about how best to do this.
How can I prevent thunderstorm asthma if I have had asthma in the past?
If you’ve had asthma in the past, talk with your doctor about your risks of epidemic thunderstorm asthma and what additional actions would be appropriate for your individual situation, particularly the need for a preventer over the grass pollen season and having practical knowledge of asthma first aid.
How can I prevent thunderstorm asthma if I have hay fever?
If you have hay fever you may also be at increased risk of asthma, particularly during an epidemic thunderstorm asthma event - around one in four people with hay fever also have asthma. If you think you may have symptoms of asthma, for example if you wheeze, are short of breath, have tightness in the chest or cough with your hay fever, then talk to you GP about determining whether they could be related to asthma.
If you have hay fever only, see your GP or pharmacist about a hay fever treatment plan and what you can do to help protect yourself from the risk of thunderstorm asthma. This may include having an asthma reliever puffer appropriately available – these are available from pharmacies without a prescription. You should also maintain good awareness of asthma first aid.
Could I experience thunderstorm asthma if I don’t have asthma or hay fever?
It’s possible you could have undiagnosed asthma. If you experience wheezing, shortness of breath, chest tightness or persistent cough, then you may have asthma.
Asthma is very common and affects about one in nine people. Many people don’t realise that you can develop asthma at any age, even as an adult. It’s important to recognise asthma symptoms and see your doctor for review if you experience any of them.
A diagnosis of asthma is more likely if you have eczema or hay fever, or have close relatives with allergies and/or asthma, and if your symptoms:
- keep coming back, or happen at the same time each year
- are worse at night or in the early morning
- are clearly triggered by exercise, allergies or infections, and improve quickly with reliever medication.
Around one in four people with hay fever also have asthma, and it is important to recognise that pollen can trigger asthma as well as hay fever symptoms.
Some people experience wheezing, breathlessness, a feeling of tightness in the chest or coughing with their hay fever and don’t realise that these may actually be symptoms of asthma. Hay fever only affects the eyes and upper airways (nose and throat) while asthma affects the lower airways (the lungs) causing the above symptoms.
If you do have asthma, the sooner you get it under control the sooner you’ll feel better and the faster you can help reduce your risk of thunderstorm asthma.
What should I do if I, or someone else, is having an asthma attack?
It’s important for everyone to know the four steps of asthma first aid. The most common symptoms of asthma are wheezing, shortness of breath, a tight feeling in the chest and a persistent cough. If you think someone is having an asthma attack:
Step 1: Sit the person upright
- Be calm and reassuring
- Do not leave them alone.
Step 2: Give 4 separate puffs of blue/grey reliever puffer
- Shake the puffer
- Put 1 puff into the spacer
- Take 4 breaths from the spacer. Repeat until 4 puffs have been taken. (If you don’t have a spacer, simply inhale 4 puffs directly by mouth).
Remember: Shake, 1 puff, 4 breaths OR give 2 separate doses of a Bricanyl inhaler (age 6 and over) or a Symbicort inhaler (over 12).
Step 3: Wait 4 minutes
Wait 4 minutes. If there is no improvement, give 4 more separate puffs of blue/grey reliever, as with Step 2 OR give 1 more dose of Bricanyl or Symbicort inhaler.
Step 4: If there is still no improvement dial triple zero (000) for an ambulance
Keep giving the person 4 separate puffs every 4 minutes until emergency assistance arrives.
Call triple zero (000) immediately if:
- the person is not breathing
- their asthma suddenly becomes worse
- the person is having an asthma attack and there’s no blue or grey reliever available.
- you are not sure if it is asthma
Remember that asthma reliever medication used in an emergency is unlikely to cause harm, even if the person doesn’t have asthma.
What resources are available to help me learn about asthma and hay fever?
The asthma videos on Kids Health Information, Royal Children’s Hospital Melbourne, will help you better understand and manage your child's asthma. If your child shows signs of severe asthma (struggling to breathe, deep sucking movements at their throat or chest), call an ambulance immediately.
About the epidemic thunderstorm asthma risk forecasting system
How does the epidemic thunderstorm asthma risk forecasting system work?
Epidemic thunderstorm asthma is thought to be caused by high grass pollen levels in the air and a certain type of thunderstorm with strong winds.
The pilot risk forecasting system requires a number of environmental and meteorological data inputs related to pollen and weather.
Weather conditions associated with epidemic thunderstorm asthma include wind changes and strong gusts typically observed with thunderstorms. This information comes from the Bureau of Meteorology's numerical weather models and weather forecasters monitoring the most recent weather observations.
Pollen forecasts are dependent on many factors including wind, temperature, rainfall, relative humidity and satellite-estimated grass coverage and condition. The current pollen forecasting model uses information about pollen counts collected over many years in Melbourne and four years across the state. Pollen collection at the current eight Victorian sites during the grass pollen season helps to verify and refine the pollen forecasting model.
The system estimates the risk of an epidemic thunderstorm asthma event for the current day, the next day, and the day after that.
The system delivers daily epidemic thunderstorm asthma risk forecasts from 1 October through to 31 December, the typical Victorian grass pollen season.
Where can I access the epidemic thunderstorm asthma risk forecast?
Epidemic thunderstorm asthma risk is forecast each year during the Victorian grass pollen season (typically 1 October to 31 December).
The risk forecast covers three days (today, tomorrow and the day after) and uses a colour-coded scale from low to high risk: green (low), orange (moderate) and red (high).
The risk forecasting system has been designed to forecast the chance of an epidemic thunderstorm asthma event occurring. It is not designed to forecast the seasonal increase in asthma and hay fever symptoms which occur every year during the grass pollen season, which can be triggered by pollen and changes in weather generally.
A low risk (green) forecast means that the elements necessary for an epidemic thunderstorm asthma event are not expected and an event is unlikely.
A moderate risk (orange) forecast means that one of the elements necessary for an event may be present (i.e. a high pollen forecast or a severe thunderstorm with strong winds) and there is a moderate chance of an epidemic thunderstorm asthma event occurring. You should be prepared and not alarmed.
A high risk (red) forecast means there is a high pollen forecast and severe thunderstorms(s) with strong winds are likely to be present. There is a higher chance of an epidemic thunderstorm asthma event occurring.
What should I do on days with increased risk?
People should be aware of the heightened risk of thunderstorm asthma in general throughout the grass pollen season and be appropriately prepared. The forecast should not replace appropriate prevention and good asthma and hay fever management, which is the best way to protect yourself from thunderstorm asthma. The forecasting system is also not designed to forecast the risk of individual's suffering asthma and hay fever symptoms, which occur every year during the grass pollen season.
- avoid exposure to any storms that may emerge, especially the wind gusts that precede them
- have a reliever appropriately available (as discussed with your doctor or pharmacist)
- remind themselves of their asthma action plan if they have one and know the .
How do I set up a watch zone to receive advice and warnings when a high risk is forecast in my area?
- Open the or the app.
- Select 'Create a Watch Zone'
- On the following screen, type your address or suburb into the search box at the top, and select your location from the suggestion list that drops down.
- You can also adjust the radius of your watch zone by selecting the plus (+) or minus (-) button.
- Once you are happy with the radius of your Watch Zone, select 'Next'
- Choose a name for your new watch zone, for example 'Asthma' and type it into the text box.
- Ensure that the 'advice warning' option is selected.
You will now receive automatic warnings that are issued in your selected Watch Zone.
How accurate is the epidemic thunderstorm asthma risk forecasting system?
The science of epidemic thunderstorm asthma risk forecasting is new and as with all forecasts, there is an element of uncertainty. The epidemic thunderstorm asthma risk forecast is based on a synthesis of the modelled grass pollen forecast combined with the forecast for a particular type of thunderstorm. These complex models have multiple inputs, including from satellite data and land and ocean-based measurements. The accuracy of the epidemic thunderstorm asthma risk forecasting system is limited by how precisely these complex phenomena can be observed and modelled.
Epidemic thunderstorm asthma events are relatively rare, and therefore, it may take some time until the accuracy can be measured with high confidence.
Additionally, the forecast only indicates whether the chance of an epidemic thunderstorm asthma event occurring is increased – a higher forecast does not mean than an event is certain to happen, nor does a lower forecast mean that an event will not happen.
People should be aware of the heightened risk of thunderstorm asthma in general throughout the grass pollen season and be appropriately prepared. The forecast should not replace appropriate prevention and good asthma and hay fever management, which is the best way to protect yourself from thunderstorm asthma.
Where are the pollen traps located in Victoria?
The Victorian pollen monitoring network comprises eight pollen traps at the following locations:
- Waurn Ponds (Geelong)
- Creswick (near Ballarat)
- Dookie (near Shepparton)
- Churchill (near Morwell)
These eight pollen traps across Victoria support the verification and refinement of the forecasting model by providing a more detailed understanding of pollen levels and the spread/movement of pollen across the state.
Where can I find data from pollen traps in my area?
As part of the epidemic thunderstorm asthma forecasting system, the Victorian Government funds grass pollen monitoring during the grass pollen season. Pollen information is provided to the Bureau of Meteorology as one important element to the epidemic thunderstorm asthma forecast, and to the public for personal use.
Information from Victoria’s eight pollen monitoring sites at Hamilton, Creswick, Bendigo, Dookie, Churchill, Parkville, Burwood and Waurn Ponds is available from the Melbourne Pollen mobile app (download from the for iOS devices or for Android devices) and .
Why is grass pollen only counted between 1 October and 31 December?
Plants release their pollen when they are flowering, and different types of plants flower at different times of year. Many deciduous trees such as birch, plane and elm flower in late winter and early spring, for example, whereas many grasses flower in the period from October to December. Research shows that grass pollen is by far the most common cause of spring hay fever (seasonal allergic rhinitis) in Victoria. The specific grass that is thought to be involved in epidemic thunderstorm asthma events in Victoria is rye grass.
Grass pollen data collected in Melbourne for more than 20 years shows that the highest levels start occurring, on average, in mid-October and fluctuate daily until the end of December. By the end of November grasses start dying off and the levels of grass pollen in the air begin to reduce. The exact start and finish of grass pollen season varies slightly from season to season but is typically from 1 October to the end of December.
How is a pollen forecast different from an epidemic thunderstorm asthma risk forecast?
Grass pollen forecasts simply reflect the expected amount of pollen in the air. They can help people with hay fever (seasonal allergic rhinitis) to prepare for these days.
Epidemic thunderstorm asthma risk forecasts combine grass pollen forecasts with the prediction of a certain type of thunderstorm thought to produce a thunderstorm asthma event.
About improving health service capacity to respond during emergencies
What is being done to help health services build their capability to respond in the future?
The Victorian Government is improving how we plan, communicate and work with our health services during emergencies.
Working with our public hospitals, we have built a system that provides the department with near real-time data on emergency department patient presentations.
The system will help the department identify a surge in hospital demand, enabling us to respond in a more timely and effective way, and improving our ability to protect the community.
The department also has a range of communications capabilities available to provide early advice and information to critical stakeholders including health services during potential and actual emergencies.
Will the monitoring system be publicly available?
The data and information in the system is protected and only used for the purposes of managing emergencies.
Visibility of the system will be provided to only those agencies with a role in assisting the department’s response during emergencies.
About other actions undertaken to prepare for similar future events
What else has the department done to improve its emergency response to similar future events?
The department has reformed the state health emergency arrangements to ensure the best system is in place to meet the community’s health needs.
What is the Government doing to improve knowledge within the community and health sector?
The department has worked with a wide range of clinical experts and consumer groups to create tools and resources to improve the prevention, diagnosis and management of asthma and hay fever, and asthma first aid within the community.
Health professional resources
The department has also supported the National Asthma Council Australia and leading health professional organisations to develop resources and deliver an epidemic thunderstorm asthma education program for health professionals across Victoria. Health professionals can access epidemic thunderstorm asthma training and resources from the and from the .
Reviewed 28 September 2023