Respiratory syncytial virus, or RSV, is one of the most common causes of upper and lower acute respiratory infections in young children worldwide. RSV acute respiratory infections appear to be increasing in frequency in the United States.
Children younger than 12 months of age who become infected with RSV are at high risk for developing subsequent wheezing that can persist as asthma a few years later. To understand why, NIAID-funded scientists examined the community of bacteria that resided in the nose and the upper part of the throat of infants when they had an RSV infection.
Wheezing, a high-pitched whistling sound made while breathing, is caused by inflammation and narrowing of the lower airways. Wheezing often is associated with difficulty breathing. Numerous illnesses can cause wheezing, with asthma being one of the most common causes in children.
A team led by scientists at Vanderbilt University School of Medicine in Nashville studied 118 RSV-infected infants, taking samples of bacteria from their noses and the upper part of their throats and following them until they were 2 years old. The researchers found that having a greater amount of the bacterium Lactobacillus in the nose or upper part of the throat during acute RSV infection in the first year of life was associated with a reduced risk of wheezing at age 2 years. This finding indicates that Lactobacillus in the upper part of the airways may protect infants from long-term consequences of an RSV infection, creating opportunities for interventions to avoid the development of wheezing and perhaps asthma. Also, this finding suggests that the level of Lactobacillus in the nose and upper part of the throat of an infant infected with RSV could help predict whether the baby is at risk for developing wheezing later in childhood.
Reference: C. Rosas-Salazar, et al. Nasopharyngeal Lactobacillus is associated with childhood wheezing illnesses following acute respiratory syncytial virus infection in infancy. Journal of Allergy and Clinical Immunology DOI: 10.1016/j.jaci.2017.10.049 (2018).