Infectious pathogens and bronchiolitis outcomes Expert Review of Anti-infective Therapy Downloaded from informahealthcare.com by Washington University Library on 01/12/15 For personal use only.
Expert Rev. Anti Infect. Ther. 12(7), 817–828 (2014)
Kohei Hasegawa*, Jonathan M Mansbach and Carlos A Camargo Jr Department of Emergency Medicine (KH, CAC), Boston, MA, USA and Department of Medicine (CAC), Division of Rheumatology, Allergy, and Immunology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA and Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA (JMM), USA *Author for correspondence: Tel.: +1 617 726 5276 Fax: +1 617 724 4050 [email protected]
Bronchiolitis is a common early childhood illness and an important cause of morbidity, it is the number one cause of hospitalization among US infants. Bronchiolitis is also an active area of research, and recent studies have advanced our understanding of this illness. Although it has long been the conventional wisdom that the infectious etiology of bronchiolitis does not affect outcomes, a growing number of studies have linked specific pathogens of bronchiolitis (e.g., rhinovirus) to short- and long-term outcomes, such as future risk of developing asthma. The authors review the advent of molecular diagnostic techniques that have demonstrated diverse pathogens in bronchiolitis, and they review recent studies on the complex link between infectious pathogens of bronchiolitis and the development of childhood asthma. KEYWORDS: acute respiratory infection • asthma • atopy • bronchiolitis • IgE • recurrent wheeze • respiratory syncytial virus • rhinovirus
Bronchiolitis is the most common lower respiratory infection in young children . Viruses are almost always the cause of this illness, which is characterized by acute inflammation, edema and necrosis of epithelial cells lining small airways, increased mucus production and bronchospasm. Although ‘bronchiolitis’ refers to inflammation of the bronchioles, this inflammation is inferred in young children with respiratory distress in conjunction with signs of an infection . Consequently, bronchiolitis remains a clinical diagnosis without a common international definition [1–4]. In the USA, the diagnosis is applied broadly but is sometimes linked to the specific physical examination finding: wheeze . In 2006, the American Academy of Pediatrics (AAP) defined bronchiolitis as a constellation of clinical symptoms and signs including a viral upper respiratory prodrome followed by tachypnea, wheezing, crackles, use of accessory muscles and/or nasal flaring in children less than 2 years of age . Most clinicians and bronchiolitis researchers outside the USA believe that the AAP definition is too broad because the distinction between bronchiolitis and recurrent breathing problems becomes increasingly difficult as the child grows beyond infancy (defined as age