Under the weather: an epidemic thunderstorm asthma event in Leicester, June 2023

Abstract

In the context of climate change and increasing global populations, thunderstorm asthma may become a greater threat at both individual and population levels. The unpredictable nature of epidemic thunderstorm asthma events makes them challenging to study; however, they can have devastating consequences. Novel approaches are required to characterise the mechanisms driving these events to allow researchers and other stakeholders to understand who is at risk and when. This will support the development of interventions that protect patients and healthcare services. In this commentary, we provide an overview of thunderstorm asthma and briefly describe an epidemic affecting Leicester, UK in June 2023. Our analysis highlights Cladosporium spores as a key player in mediating UK thunderstorm asthma. Low levels of background treatment in adults and an increase in emergency assessments but not hospitalisations in children suggest that epidemics could be prevented by improving awareness and ensuring access to standard inhaled therapies. Finally, we consider future risk and suggest research priorities with an ultimate goal of minimising the adverse impact related to thunderstorm asthma going forward.

Keywords: Allergic lung disease; Asthma; Clinical Epidemiology; Paediatric asthma.

Figure 1. UK Health Security Agency (HSA) data for England demonstrating trends in emergency department attendances for acute asthma from Autumn 22 to Autumn 23, with (A) overall spikes at the time of thunderstorms on 12 and 18 June 23, (B) spikes in patients aged 5–64 and (C) spikes across all regions of England with the exception of the North East. Figures adapted from the Emergency Department Syndromic Surveillance System Bulletin (England), 2023, Week 35 with permission as per the terms of the Open Government License (OGL) V.3.0. EDSSS, emergency department syndromic surveillance system.

Figure 2. University Hospitals of Leicester NHS Trust (A) emergency department (ED) attendances and (B) hospitalisations for acute asthma in adults (red) and asthma or viral wheeze in children (green) across June 2023. Vertical dotted lines indicate thunderstorm days. Adult hospitalisations for acute asthma represent admissions to Glenfield Hospital site only. NHS, National Health Service.

Figure 3. Cladosporium spore counts, (A) grass pollen counts (B) and adult asthma emergency department (ED) attendances (C) May–August 2023. Thunderstorm days on 12, 18 and 22 June 2023 are indicated by the grey columns. Black dotted lines indicate average spore (A) and pollen (B) levels based on 17 years of data collected in Leicester, UK. Orange dotted line indicates allergenic threshold of 3000 spores/m³ for Cladosporium (A). Green dotted line indicates allergenic threshold of 50 pollen grains/m³ for grass (B).

Figure 4. 10 most abundant fungal spore categories recorded for June 2023. Thunderstorm days on 12, 18 and 22 June 2023 are indicated by the grey columns.