Identifying opportunities for preventing respiratory infections in children through integrating population-based health and laboratory data

Hannah C Moore, Peter Jacoby, Faye Janice Lim, Parveen Fathima, Tasnim Abdalla, Roseanne Barnes, Nicholas de Klerk, Deborah Lehmann, Kim Carter, David Hendrickx

This project investigates the epidemiology of acute lower respiratory infections in young children. The pathogens most commonly associated with acute lower respiratory infections include respiratory syncytial viruses, influenza viruses, parainfluenza viruses, rhinoviruses, adenoviruses, Streptococcus pneumoniae and Bordetella pertussis.

Some pathogens are found simultaneously in children with respiratory infections (known as co-infection) and there is mixed evidence to suggest that co-infection results in worse clinical outcomes than single infection.

This project will use data linkage to investigate the pathogen-specific burden of acute lower respiratory infections in terms of hospitalisations and emergency department presentations between 1996 and 2012 in a total population cohort of Western Australian children.

The specific aims of this project are:

1. To quantify the pathogen-specific burden of acute lower respiratory infections in Western Australia using individually-linked laboratory, hospitalisation, emergency department and disease notification datasets;
2. To assess the impact of viral-viral and viral-bacterial co-infections on respiratory infection outcomes and document the relative contribution of individual respiratory pathogens to these outcomes and;
3. To evaluate the direct and indirect population impact of paediatric immunisations on hospitalisations and emergency department presentations for acute lower respiratory infections, their related conditions (such as febrile convulsions) or other vaccine-preventable infections by conducting pre- and post-vaccination introduction temporal trend analyses.
4. To describe the burden of respiratory infections in relation to the observed burden of skin infections in Western Australia between 1996 and 2012, in terms of the age-specific admission rates across geographical regions.

The majority of the analyses have been completed and are being written up for publication. Some of our key findings to date include:

• Skin infections are an important cause of hospital admission with admission rates being 15 times higher in Aboriginal (32/1000) than in non-Aboriginal children (2/1000)
• Seasonality of RSV differs across the state with clear peaks in the middle of winter for temperate regions like Perth, but less clear seasonality in the tropical regions such as the Kimberley
• Not all detections of notifiable diseases including pertussis, influenza and invasive pneumococcal disease are captured by the notifiable disease datasets indicating that a combination of datasets from notifiable disease datasets and routine laboratory data are needed to accurately capture burden of disease
• Viral testing rates in children admitted to hospital have increased from 2000-2012 with large yearly fluctuations with specimens undergoing molecular testing increasing from 5-87%
• 38% of hospital admissions where there was test for detection of respiratory viruses did not have a respiratory infection diagnosis code, indicating that diagnosis codes alone do not adequately capture respiratory infections in children
• Respiratory Syncytial Virus (RSV), influenza virus and parainfluenza virus are the most common viruses detected in hospitalised children
• Hospitalisation rates for pneumonia have continued to decline in children, following on from our observations noted previously in 2011. The pathogens identified in children diagnosed with pneumonia varies between Aboriginal and non-Aboriginal children
• ¼ for all emergency department presentations are for acute respiratory infections.

Plain Language summary: Chest infections, like influenza and pneumonia, are a major cause of illness in children, particularly in Aboriginal children. By bringing together information that is stored on public records, we will describe the viruses and bacteria that are associated with chest infections in Western Australian children over a 16 year period. Some of our key findings highlight that 2 of the most common viruses in children are not vaccine preventable and respiratory infections are still a major cause of hospital admission and presentation to emergency departments.

Funder: NHMRC Project Grant APP1045668

External collaborators: Christopher Blyth (UWA); Alexandra Hogan, Kathryn Glass (Australian National University, ACT, Australia)