What is thunderstorm asthma?

Thunderstorm asthma had previously been considered unlikely to occur in New Zealand due to our weather patterns not thought to pose a risk. However, recent climate changes have challenged this perception, with New Zealand experiencing its first thunderstorm asthma event in 2017. So what is thunderstorm asthma and what can be done to prepare for another event here in the future?

Thunderstorm asthma begins when a significant thunderstorm coincides with a significant amount of pollen in the air, usually in spring or summer. Pollen grains are sucked into the storm clouds, where they absorb moisture and burst, shattering into smaller pieces. These very tiny pollen particles are spread by the storm’s downdrafts. These pollen particles are so small that they pass straight through the nose and into people’s lungs, where they can trigger an immediate asthma flare-up. Usually ordinarysized pollen grains are big enough to be caught by nasal hairs, however it’s these much smaller pollen fragments that are the cause of thunderstorm asthma.

However, despite being in recent headlines, thunderstorm asthma is not that common. In fact, it requires the perfect combination of factors to occur. This includes, the right type of thunderstorm, a strong up-draft, during pollen season, and at a time when many people are outdoors.

Thunderstorm asthma can affect people of any age, and is more likely to cause flare-ups in people who have asthma or have had asthma in the past. It may also impact those who get seasonal hay fever that is triggered by pollen (also known as allergic rhinitis). The risk of thunderstorm asthma is highest in adults who are sensitive to grass pollen and have seasonal hay fever (with or without known asthma).

What is concerning, is that a significant proportion of people severely affected by thunderstorm asthma have undiagnosed asthma, and as a result, may not have access to medication to treat an asthma flare-up, or be slower to seek medical attention as they do not recognise the symptoms of asthma. These people are unfortunately often at a greater risk of having more serious complications from a thunderstorm asthma event.

Thunderstorm asthma is a well-known phenomenon in other parts of the world where the weather conditions are more likely to produce thunderstorm asthma events. In Australia, thunderstorm asthma is so prevalent that public health warnings are issued when there is a likely chance of an event occurring. When this happens, the impact can be very serious. For example, a storm in Melbourne in November 2016 sent 8,500 people to emergency departments, overwhelmed ambulance services, and resulted in at least 10 people dying of asthma-related causes from this event.

Despite having thought the risk to of a New Zealand thunderstorm event was minimal, a Waikato storm back in 2017 brought about New Zealand’s first-ever recorded thunderstorm event. The event saw an sudden increase in severe asthma cases presenting to Waikato Hospital, with these people becoming the first to be diagnosed with thunderstorm asthma in New Zealand.

A study of this storm published in 2020 – ‘Thunderstorm-related asthma can occur in New Zealand’ – showed that this event resulted in 14 people presenting to Waikato Hospital’s emergency department with asthma symptoms within 48 hours of the storm, some of which had never experienced asthma symptoms before. In addition to this, during the same time period, Anglesea Accident and Medical Centre, an urgent 24-hour clinic in Hamilton, saw 24 patients with asthma symptoms.

GPs interviewed by the authors of the study also reported an increase in people presenting with asthma symptoms in the four to five days following the thunderstorm. It is also likely that many other people experienced milder respiratory symptoms as a result of the storm, but chose not to seek medical attention.

Accurately documenting thunderstorm asthma events is an important first step in making a plan that would enable paramedics and emergency facilities across New Zealand to respond to any larger scale events here in the future.

However, prevention is also key – people who have asthma or hay fever should ensure that their condition is well managed and that there is a plan in place for emergency situations. Plans should include what preventive medications you can take to manage your condition and what you should do when symptoms worsen. Additionally, medication should always be on-hand in case of an asthma emergency, or thunderstorm asthma event.

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