Published Online: November 2014
The role of infection in asthma is varied in that it may exacerbate established asthma or be a contributing factor to the initial development of asthma. In a review article in The Journal of Allergy and Clinical Immunology: In Practice, Darveaux and Lemanske summarize current knowledge regarding the relationships between infection and asthma. For asthmatic individuals, infections may be the only reason for exacerbations, or only one of many factors impacting the frequency and severity of exacerbations. Environmental, pathogen and several host factors influence the response to infections in asthma. There is evidence that viruses, particularly human rhinovirus (HRV) and respiratory syncytial virus (RSV), are involved both in the development of asthma and often are a trigger for exacerbations. Additionally, infection with several bacterial species are associated with recurrent wheezing and asthma exacerbations.
Clinically, infections with various viruses are often indistinguishable and may not be symptomatic. Nasal discharge, congestion, cough and sore throat are common among adults and children. In adults, fever is not typical and symptoms often last longer, up to 10 days or more. Bacterial infections are considered when symptoms last more than 10 days, or in children with high fevers that persists ≥4 days.
Most asthma exacerbations in children and adults are attributed to respiratory viral infections, with HRV accounting for nearly two thirds of them. Symptoms of wheezing and decreased lung function typically begin 1-2 days after symptoms of infection begin, and return to baseline within 5-10 days. Repeated exacerbations are associated with loss of lung function over time.
Several genetic mutations have been identified as risk factors for early life wheezing, increased infection severity, or the development of asthma after exposure to certain infections at an early age. Medical conditions that may influence the risk of infection or asthma control during respiratory infections include allergic rhinitis, food allergy, eczema, gastroesophageal reflux disease (GERD), as well as other respiratory tract diseases. Laboratory testing is rarely necessary, but may include a complete blood count and chest X-ray. Occasionally, bacterial cultures are taken to help direct antimicrobial therapy.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.