Environmental and occupational respiratory disorders
Epidemic asthma and the role of the fungal mold Alternaria alternata

https://doi.org/10.1016/j.jaci.2007.04.045Get rights and content

Background

After July 29, 2002, an epidemic of asthma admissions was associated with a thunderstorm in the United Kingdom.

Objective

We sought to study the cause of epidemics of asthma associated with thunderstorms.

Methods

We performed a case-control study of 26 patients presenting to Cambridge University Hospital with asthma after the thunderstorm. Control subjects were 31 patients with summer seasonal asthma. Subjects underwent skin tests and specific IgE serology to inhaled aeroallergens. Meteorologic and aerobiologic data correlated with asthma admissions were analyzed.

Results

Twenty-three of 26 cases had IgE sensitization to Alternaria species. Eleven of 31 control subjects gave a history of asthma exacerbation during thunderstorms. Ten of these 11 control subjects were sensitive to Alternaria species on skin testing, but Alternaria species sensitivity was only identified in 4 of the 20 remaining control subjects who did not report thunderstorm-related asthma symptoms. The odds ratio of having epidemic thunderstorm-related asthma if sensitive to Alternaria species was 9.31 (95% CI, 2.305-37.601; P = .0008) and 63.966 (95% CI, 3.577-1143.9; P < .0001) if sensitive to Alternaria species, Cladosporium species, or both. Poisson regression analysis showed that counts of broken Alternaria species and Didymella and Cladosporium species were significantly correlated with each other and with asthma admissions. The thunderstorm was associated with increased levels of Alternaria, Cladosporium, and Didymella species.

Conclusions

Alternaria alternata sensitivity is a compelling predictor of epidemic asthma in patients with seasonal asthma and grass pollen allergy and is likely to be the important factor in thunderstorm-related asthma.

Clinical implications

Alternaria species sensitization in asthmatic subjects with grass pollen sensitivity predicts susceptibility to thunderstorm-associated asthma.

Section snippets

Methods

The study was approved by the local research and ethics committee. Investigation was by means of case-control study of 26 case patients who presented to the hospital with acute asthma during the outbreak and 31 control subjects with seasonal asthma during the grass pollen season. Informed written or verbal consent was obtained from cases and control subjects.

Cases

Ninety-two patients older than 16 years attended the Cambridge University hospital ED with asthma between July 29 and August 5. Based on data for July from August 1999 from 2001, expected attendances would have been 8 to 9 patients over this period. Fifty-seven patients with asthma attended the hospital on July 29-31. Eight subjects younger than 18 years were excluded, 1 subject had left the country, and 22 did not attend follow-up or were not contactable and therefore were not included in the

Discussion

The fungal spores of Alternaria and Cladosporium species are known to cause allergic sensitization and seasonal asthma symptoms. In the United Kingdom in July and August (at the end of the grass pollen season), environmental levels of these spores increase rapidly, and allergic sensitization correlates with the severity of asthma symptoms.11 In sensitive individuals inhalation of Alternaria species spores results in an asthmatic response, followed by an increase in bronchial hyperresponsiveness.

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  • Cited by (0)

    Disclosure of potential conflict of interest: C. Bryden is employed by the Met Office. The rest of the authors have declared that they have no conflict of interest.

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