The Consequence of Respiratory Syncytial Virus (RSV) Infection in Young Infants

Background: Respiratory syncytial virus (RSV) is the most common cause of childhood illness which attack the lower respiratory tract and develop bronchitis and pneumonia. Approximately 70% of infants are infected with RSV during their first year of life, and almost all children are infected at least once by 2 years of age (Wu & Hartert, 2011).

Each year, an estimated 33·1 million episodes of RSV-associated acute lower respiratory infections occur among under-five children globally, leading to 3·2 million hospitalizations and 118,200 deaths (Ting Shi & Acacio, 2017). The burden of RSV-associated severe acute lower respiratory tract infection is 10 times higher in developing countries compared to that in developed countries (36.1 per 1000 life birth vs 3.2 per 1000 life birth, respectively).

In addition to acute mortality and morbidity, RSV infection has a long-term effect on children's health (Jat & Kabra, 2017; Kneyber, Steyerberg, de Groot, & Moll, 2000). RSV infection can induce a state of bronchial hyper-reactivity that has an association with the development of asthma in later life (Balfour-Lynn, 1996), which, in turn, is a major risk factor of chronic obstructive pulmonary disease in adulthood (Svanes et al., 2010).. The prevalence of wheezing and asthma were reported two times higher in the children who had RSV bronchitis in infancy compared with children without a history of bronchiolitis during infancy (Sigurs et al., 2010). In a report, it was shown that among the children who experienced asthma by school age, 31% of them had healthcare visits in infancy due to respiratory diseases (Wu & Hartert, 2011). The severity of the RSV associated illness was reported as an additive factor for asthma risk. Hartert et, al., reported that asthma prevalence was two times higher in the infants who were hospitalized for RSV infection compared to the other who received care at the outdoor department (Wu & Hartert, 2011). In the mouse model, it was found that viral infection in neonatal rats delayed the growth of secondary septa, decreased the alveolar surface density by 14 to 26%, and reduced the diameter of terminal bronchioles by 11 and 20% (Castleman, Sorkness, Lemanske, Grasee, & Suyemoto, 1988). However, there is no data on the effect of RSV infection on the lung of neonates. In human, the lung remains premature at birth and continue to develop for 2-3 years postnatally and can be assumed that the impact of RSV infection during early infancy would be very severe.

Collecting clinical samples from young infants and lack of appropriate diagnostic to detect RSV virus are the major obstacles to study RSV infection in developing countries. No study from developing countries has investigated the long-term effect of RSV infections incurred during the young infant period. It is assumed that the long-term effect of RSV infection might be more intense if infection occurs during this period, as the lungs of newborns continue to develop for the first several months of life.

Recently, a study aimed to determine the etiology of young infant infection at five centers of three South Asian countries (Bangladesh, India, and Pakistan). This study identified 474 young infants who had laboratory-confirmed RSV infection; additionally, this study tested specimens from 1,873 age and sex-matched healthy infants, which were found to be negative for RSV. The current age of that cohort is between 5 and 7 years, which provides a unique opportunity to gather information on the long-term effect of RSV infection in a large number of laboratory-confirmed cases at a low cost.