Rhinoviruses are the most common pathogens in the upper and lower respiratory tract of infants in their first year of life, according to findings from a study of 263 infants in an upper-class community who were followed up from birth until 1 year of age.
Although respiratory syncytial virus (RSV) accounts for many acute respiratory illnesses that are severe enough for hospitalization, other pathogens have been underrecognized because it is difficult to identify them, reported Dr. Merci Kusel of the University of Western Australia in West Perth and colleagues.
The expanded use of polymerase chain reaction detection gives physicians a look at the pathogens behind respiratory tract illnesses. Nasopharyngeal aspirates were collected from children during 984 episodes of acute respiratory illnesses and compared with 456 control samples taken when the children were healthy (Pediatr. Infect. Dis. J. 2006;25:680–6).
Rhinoviruses appeared in 52% of upper respiratory tract illnesses (URIs), 41% of lower respiratory tract illnesses (LRIs), and 45% of LRIs with wheezing. By comparison, RSV appeared in 9% of URIs, 15% of LRIs, and 17% of LRIs with wheezing. Additionally, parainfluenza viruses appeared in 5% of URIs and 7% of LRIs, and human metapneumoviruses appeared in 3% of LRIs.
Rhinoviruses were the viruses most often detected in both LRIs and URIs, but rhinoviruses were twice as likely to cause URIs as LRIs in the cases when these viruses were detected. The other pathogens (RSV, parainfluenza, and human metapneumovirus) were equally likely to cause either URIs or LRIs. Rhinoviruses may have a particular affinity for the upper respiratory tract in infants younger than 1 year of age, but additional research is needed in a diverse population, they noted.