Thunderstorm Asthma
For patients with asthma, wildfires, storms, heavy rainfall, and thunderstorms can lead to exacerbations. Emergency room visits and hospital admissions generally increase after extreme weather events.
A study examining the consequences of the fires in California from 2004 to 2009, for example, reported that hospital visits related to asthma increased by 10.3%. Those related to respiratory problems increased by 3.3%. Infants and children up to age 5 years were most affected.
Thunderstorms are increasing because of global warming. Thunderstorm asthma arises under specific meteorological conditions. It typically occurs in patients with aeroallergies (eg, to pollen and fungal spores) in combination with thunderstorms and lightning. Large pollen grains, which normally remain in the upper airways, ascend into higher atmospheric layers and break apart due to updrafts. These very small particles are pushed back to ground level by downdrafts, enter the lower airways, and cause acute asthma.
Worldwide, cases of thunderstorm asthma are rare. About 30 events have been documented. Thunderstorm asthma was first observed in 1983 in Birmingham, England. Fungal spores were the trigger.
The most significant incident so far was a severe thunderstorm on November 21, 2016, in Melbourne, Australia. Worldwide attention was drawn to the storm because of an unusually high number of asthma cases. Within 30 hours, 3365 patients were admitted to emergency rooms. “This is also a high burden for a city with 4.6 million inhabitants,” said Dr. Elmer. Of the patients in Melbourne, 35 were admitted to the intensive care unit and 5 patients died.
Dr. Elmer calculated the corresponding number of patients for Wiesbaden and Mainz. “Assuming a population of 500,000 in this region, that would be 400 patients in emergency rooms within 30 hours, which would be a significant number.”
Such events are mainly observed in Australia, where two events per decade are expected. However, due to climate change, the risk could also increase in Europe, leading to more cases of thunderstorm asthma.
Risk Factors
The following environmental factors increase the risk:
- High pollen concentrations in the days before a thunderstorm
- Precipitation and high humidity, thunderstorms, and lightning
- Sudden temperature changes
- Increases in aeroallergen biomass and extreme weather events because of climate change
In Australia, grass pollen was often the trigger for thunderstorm asthma. In the United Kingdom, it was fungal spores. In Italy, olive pollen has a similar potential.
Patients with preexisting asthma, uncontrolled asthma, and high serum-specific immunoglobulin E levels are at risk. The risk is also increased for patients with poor compliance with inhaled steroid (ICS) therapy and for patients who have previously been hospitalized because of their asthma.
Patients with hay fever (ie, seasonal allergic rhinitis) have a significantly higher risk. As Dr. Elmer observed, 88% of patients in the emergency room in Melbourne had seasonal allergic rhinitis. “Fifty-seven percent of the patients in the emergency room did not have previously known asthma, but more than half showed symptoms indicating latent asthma. These patients had latent asthma but had not yet been diagnosed.”
Dr. Elmer emphasized how important it is not to underestimate mild asthma, which should be treated. For patients with hay fever, hyposensitization should be considered.