Vaccine and Infectious Disease Division

Detection of pediatric viral pathogens

Respiratory infections are one of the most common reasons for pediatric hospital admission, especially in children <24 months of age. Several viruses cause respiratory illness, including influenza, respiratory syncytial virus (RSV) and metapneumovirus, and can frequently require inpatient and intensive care unit (ICU) hospitalization. RSV infection alone is responsible for an average of 100,000 pediatric hospitalizations per year nationwide.

VIDD scientists have previously developed tools for sensitive detection of viral pathogens in hospitalized children in which viral nucleic acid is amplified and characterized by polymerase chain reaction (PCR) and requires very small nasal wash samples. These technological advances have allowed for identification of multiple viruses during co-infection of a single patient, and VIDD scientists have used these methods for identifying potential correlations between disease severity and viral load in single and multiple viral respiratory infections.

VIDD affiliate senior research scientist Dr. Jane Kuypers, member Dr. Anna Wald and affiliate investigator Dr. Janet Englund analyzed nasal wash samples from children admitted for respiratory illness at Seattle Children’s Hospital from September 2003 to September 2004 for the presence and viral load of several viruses: adenovirus, RSV A and B, human metapneumovirus, influenza A and B, parainfluenza 1-4 and four subtypes of coronavirus. Nasal samples and clinical data were available from 893 children; 64 percent were hospitalized in the inpatient ward and 12 percent in the ICU, and the median patient age was 16 months. The authors detected at least one viral infection in 63 percent and more than one virus in 18 percent of the patients. There was no association between gender and number of viral infections but a correlation was observed between age and viral infection; multiple viruses were more frequent in older (6-24 months) compared to younger (0-6 months) children.

An interesting and somewhat counterintuitive finding was that children with single virus infection had higher rates of severe disease than those infected with multiple respiratory viruses as measured by inpatient and ICU admission, hospital stays >3 days and need for supplemental oxygen. Adenovirus and parainfluenza-1 were found at higher viral loads in multiple versus single virus illness while viral load of certain viruses, including RSV, influenza A and parainfluenza-3, were consistently high regardless of the viral population. This study is, to-date, the largest to analyze multiple versus single virus presence from clinical samples within 24 hours of patient evaluation and suggests that viral load may serve as a valuable marker for determining the virus most likely to cause severe disease in multiply-infected children. 

Martin ET, Kuypers J, Wald A, Englund JA. Multiple versus single virus respiratory infections: viral load and clinical disease severity in hospitalized children. Influenza Other Respi Viruses. 2012 Jan;6(1):71-7.