NIAID-funded researchers have found that combined viral and bacterial infections are associated with the increase in asthma symptoms that many children experience during the fall. Children infected with rhinovirus, which causes colds, and certain types of bacteria were most likely to experience asthma attacks and cold symptoms. While rhinovirus infection is widely thought to be the main contributor to fall asthma attacks, this study suggests that bacterial infections also play a role. The results are published in the May 2014 issue of the Journal of Allergy and Clinical Immunology.
Asthma attacks among children increase in early autumn, leading to a sharp rise in asthma-related doctor visits and hospitalizations. Colds due to rhinovirus also peak each fall when children return to school. Viral infections are a known trigger for asthma attacks, leading doctors to believe that rhinovirus is largely responsible for the seasonal increase in asthma problems.
In 2010, researchers monitoring children with asthma at the University of Wisconsin, Madison, an NIAID-supported Asthma and Allergic Diseases Cooperative Research Center (AADCRC), reported that 90 percent of the children were infected with rhinoviruses during September. However, while some of the rhinovirus-infected children experienced severe cold and asthma symptoms, others remained symptom-free. The scientists reasoned that additional factors, such as bacterial infections, may influence fall illnesses and the rise in asthma attacks.
In the current study, AADCRC researchers tested nasal mucus from 308 children with and without asthma for the presence of rhinoviruses and three common bacterial pathogens. With their parents’ help, children aged 4 to 12 collected nasal samples weekly for five weeks during the fall and kept a diary of their cold and asthma symptoms.
The scientists found that rhinovirus infections typically coincide with or precede bacterial infections. The presence of rhinovirus in nasal mucus increased the likelihood of detecting bacteria in the same sample or the following week’s sample. In contrast, the presence of bacteria did not increase the chance of viral detection the following week.
The researchers next investigated potential links between bacterial infection and the severity of asthma and cold symptoms. Children reported more symptoms during weeks when rhinovirus or the bacterium Streptococcus pneumoniae was detected in nasal mucus. Symptoms tended to be even more severe during weeks when both pathogens were present. Among the 166 children in the study with asthma, attacks were most frequent during weeks when both rhinovirus and S. pneumoniae were present in nasal samples. Detection of rhinovirus together with another bacterium, Moraxella catarrhalis, also was associated with higher numbers of colds and asthma attacks than detection of rhinovirus alone.
Overall, the scientists found that only 11 percent of the 291 illnesses recorded during the study were linked to the presence of rhinovirus alone. Rhinovirus and bacterial infections occurred together during approximately 50 percent of illnesses, while 30 percent were associated with bacterial infection alone.
The results of this study suggest that bacterial pathogens such as S. pneumoniae contribute to asthma and cold symptoms during the fall, challenging the conventional view that rhinovirus infections are the only cause of the seasonal increase in asthma-related health problems. If confirmed in other studies, these findings could lead to development of new strategies to prevent and treat asthma in the fall.
As part of the NIAID-funded PROSE study, which compares the effectiveness of different asthma treatments during the fall, investigators collected nasal mucus samples from inner-city children with asthma. Researchers plan to analyze these samples for the presence of rhinoviruses and bacteria.
Kloepfer KM, Lee WM, Pappas TE, Kang TJ, Vrtis RF, Evans MD, Gangnon RE, Bochkov YA, Jackson DJ, Lemanske RF, Gern JE. Detection of pathogenic bacteria during rhinovirus infection is associated with increased respiratory symptoms and asthma exacerbations. Journal of Allergy and Clinical Immunology (2014)
Last Updated May 05, 2014
Last Reviewed May 05, 2014