An epidemic of thunderstorm asthma in Melbourne 2016: asthma, rhinitis, and other previous allergies

Abstract

BackgroundOn 21st November 2016, Melbourne experienced an epidemic of ‘thunderstorm asthma.’ Although previously described in the literature, risk factors and natural history remain incompletely understood.ObjectiveOur aim was to follow up those presenting to the 3 Emergency Departments (EDs) in our health service during the epidemic, and assess their history for previous asthma, rhinitis, and allergies.MethodsED notes of all respiratory presentations within 48 hours of the thunderstorm event were reviewed and patients with acute asthma included. A standardised questionnaire was devised encompassing asthma diagnosis, undiagnosed asthma symptoms and rhinitis severity. Patients were contacted by phone within 30 days of the event.ResultsThree hundred forty-four patients were identified overall; 263 patients were contactable and completed a phone or mail questionnaire. The mean age was 32.7 ± 19.2 years (range, 6 months–87 years; 25% < 18 years) with 58% male sex. A previous diagnosis of asthma was present in 42% (n = 111), and there was no previous asthma diagnosis in 58% (n = 152). Of those who had no asthma diagnosis 53% had probable undiagnosed asthma. Overall, rhinitis prevalence was 88%, of which 72% were moderate or severe (Allergic Rhinitis and its Impact on Asthma guidelines) and 51% (n = 133) reported a history of grass pollen allergy.ConclusionOur data highlights the importance of atopy and rhinitis as risk factors for epidemic thunderstorm asthma. Better identification of undiagnosed asthma, and implementing treatment of asthma and rhinitis may be important.

Beta‐blocker use is an independent risk factor for thunderstorm asthma

“…Beta‐blockers may therefore be a modifiable risk factor for TA in asthmatics. In non‐asthmatics, TA is unpredictable; however, other studies report that 41–53% of ‘non‐asthmatics’ in TA16 had probable undiagnosed asthma . Hence, if clinicians screen for and diagnose asthma, beta‐blockers may also be a modifiable risk factor for TA in some ‘non‐asthmatics’.…”

“…Based on previous work, a small number of factors were examined in a multivariable logistic regression with control versus TA16 as the outcome variable and the following as independent variables: age (found by preliminary graphic analysis to be approximately linearly related), gender, born in Asia, past history asthma, past history hayfever, beta‐blocker and aspirin or NSAIDs use. Aspirin and NSAIDs use were combined for analysis due to their low frequencies.…”

“…Ten deaths were attributed to this TA event and 35 patients required intensive care admission . Furthermore, some patients continued to suffer with asthma exacerbation weeks after the event . Therefore, it is important to understand the risk factors for TA so that these can managed, thereby minimising the public health and personal impact of future events.…”

“…A general belief is that during pollen season, thunderstorms can significantly increase the levels of airborne pollen, by wind/plume action on ground level pollen, and through osmotic effect, break up pollens into particles, which are small enough to bypass the nasal passages and enter the lungs directly, triggering asthma . Recent studies of TA16 identified hayfever, asthma, younger age and Asian country of birth as risk factors for TA cases presenting to hospital . The focus of previous TA studies has been of the aetiological link between pollen exposure, hayfever, pre‐existing asthma and TA .…”

“…Recent studies of TA16 identified hayfever, asthma, younger age and Asian country of birth as risk factors for TA cases presenting to hospital . The focus of previous TA studies has been of the aetiological link between pollen exposure, hayfever, pre‐existing asthma and TA . Smoking has been studied and shown not to be a risk factor for TA .…”