We conducted this study to determine the contribution of respiratory viruses in 202 hospitalized children (1mo-5 yr) with clinical evidence of acute lower respiratory tract illness (ALRI). Nasopharyngeal specimens were assayed for viruses detection by indirect immunoflourescent method. Viral agents were identified from 109 (54%) cases (9 cases had dual infection). The most commonly detected virus was parainfluenza virus 3 in 32 (15.8%) cases followed by respiratory syncytial virus 26 (12.9%); parainfluenza 1 and parainfluenza 2 each 13 (6.4%); influenza A 16 (7.4%), influenza B; 7(3.5%), and adenovirus 12 (5.9%). There were no demographic, clinical, radiologic or laboratory parameters except for recurrent wheeze (OR: 4.47; (95% CI: 1.98-10.73) and fever (OR: 3.27; (95% CI: 1.73-6.20), which could differentiate between patients with or without viral etiology.

Key words: Acute respiratory infections (ARI), Etiology, Iran, Virus.

The etiology of acute lower respiratory illness (ALRI) is variable, depending on the age of the patients, geographic location, the time of the year, the epidemiological situation, and above all, the diagnostic methods used(1-3). Etiologic diagnosis is important in choosing the most appropriate treatment protocol(4,5).

We conducted this study to determine the relative contribution of different respiratory viruses in hospitalized young children with ALRI. Another objective was to identify the parameters on admission that may differentiate between a viral and non-viral ALRI episode.

Based on the presence or absence of virus in samples, patients were categorized into two groups (virus positive vs negative). Odds ratio (95% CI) was computed to compare the demographic and clinical, radiological, and laboratory findings of the two groups.

Of 1339 children with ALRI, 202(15%) were hospitalized. One or two viruses were identified from 109 (54%) of them (9 cases dual infection). PI₃ was detected in 32 (15.8%) cases, followed by RSV, 26 (12.9%); Inf A, 15 (7.4%); PI₁, and PI₂ each 13 (6.4%); adenovirus, 12 (5.9%) and Inf B, 7 (3.5%). Table I compares the demographic features, clinical, radiologic and laboratory findings, and antibiotic prescriptions of children with and without a detected viral agent. Children with viral etiology were more likely to have fever and history of recurrent wheezing.

In this study one or two viruses were identified from 109 out of 202 (54%) patients using viral agents detection method (IFA). Expect for RSV activity, the patterns of occurrence were generally similar to other reports in temperate regions(1-3,6,7).

The result of previous studies has also suggested that viruses are the most common causes of recurrent wheezing-associated ALRI occurring in young children(8). Thus, the preliminary diagnosis of a viral infection in absence of an obvious bacterial focus of infection coupled with recurrent wheeze should help contain indiscriminate use of antibiotic in patients with ALRI.

The most important limitations of this study were a relatively small sample size, inclusion of only hospitalized children, interrupted periods of study, and absence of highly sensitive diagnostic methods.

The findings expand our knowledge about the epidemiological features of respiratory viruses in hospitalized children with clinical evidences of ALRI in Mazandaran province, North of Iran.

The researches are grateful to Alaei A, Eshghi MR, for sampling and data collection, Enayati AA for his assistance in manuscript reviewing.

Contributors: All authors were involved in study design, planning, data collection, review of literature, analysis of results and drafting the manuscript.

Funding: Vice-chancellor for research of Mazandaran University of Medical Sciences.

Competing interests: None stated.