"Spike" in acute asthma exacerbations during enterovirus D68 epidemic in Japan: A nation-wide survey.

Background: In September 2015, Japan experienced an unusual increase in acute asthma hospitalizations of children that coincided with an enterovirus D68 (EV-D68) epidemic. The objective of this study is to investigate whether EV-D68 had a causal relationship with the spike in asthma hospitalizations.

Methods: A nation-wide retrospective survey of asthma hospitalizations of children was performed for the period from January 2010 through October 2015. The Japanese Society of Pediatric Allergy and Clinical Immunology asked its affiliated hospitals to report monthly numbers of hospitalizations, ICU admissions and mechanical ventilations due to acute asthma exacerbation. The data were retrieved from medical databases using predefined search criteria: diagnosis of asthma or asthmatic bronchitis, admission, and age <20 years. Monthly numbers of EV-D68 detection were also obtained from the Infectious Disease Surveillance Center of Japan. A Granger causality test was used to analyze the association of EV-D68 detections for asthma exacerbation.

Results: A total of 157 hospitals reported 87,189 asthma hospitalizations, including 477 ICU admissions and 1193 mechanical ventilations, during the survey period of 5 years and 10 months. The numbers of these events increased drastically in September 2015. The Granger causality test verified the association between EV-D68 and asthma hospitalizations/mechanical ventilations. The most-affected age group was 3-6 years old.

Conclusions: The spike in pediatric asthma hospitalizations in Japan in September 2015 was found to be associated with the EV-D68 epidemic. Respiratory pathogens can cause "epidemics" of asthma exacerbation. Coordinated surveillance of infectious diseases and asthma may be beneficial for prevention and better control of both illnesses.