Lower respiratory tract infections

Poor indoor and outdoor air quality increases the risk of lower respiratory tract infections among children

Lower respiratory tract infections (LRTI) refer to infections of the windpipe (trachea), lungs, and airways (bronchi, bronchioles). These include pneumonia, bronchitis and bronchiolitis. Household crowding [1], second-hand smoke exposure [2], indoor dampness and mould [3], and outdoor air pollution [4] increase the risk of lower respiratory tract infections in young children.

LRTI is responsible for a large burden of avoidable mortality and morbidity among young children under five years old globally. Compared with other developed countries, New Zealand has high rates of LRTI hospitalisation among young children [5]. Each year, a small number of children in New Zealand die from lower respiratory tract infections. Between 2001 and 2018, 173 children under five years of age died from lower respiratory tract infections, an average of 10 deaths every year.

The COVID-19 pandemic

Throughout 2020 and 2021 the New Zealand Government pursued an elimination strategy for COVID-19. A four-level COVID-19 alert system was in place from March 2020 to December 2021. Measures used in the system included temporary border closures, quarantine requirements, community testing, school closures, contact tracing, and lockdowns. A full national Level 4 lockdown was in place from 25 March 2020 to 27 April 2020 followed by Level 3 and Level 2 restrictions throughout much of the 2020 winter cold and flu season. 

In 2021 the only full national Level 4 lockdown was between 17 August 2021 and 31 August 2021. Outside of this period, regional Level 4 and 3 restrictions were used (particularly in the Auckland region), but lower level restrictions were in place for much of the cold and flu season across the country.

The total number of LRTI hospitalisations in 2023 was similar to 2022

In 2023, hospitalisations due to LRTI in children under five reached 10158, slightly higher than the 9958 hospitalisations in 2022. These numbers are consistent with hospitalisations before the COVID-19 pandemic (Figure 1).

Figure 1: Number of lower respiratory tract infection hospitalisations in children aged 0–4 years, 2004–2023

Usual winter LRTI hospitalisation peak still evident, but admissions higher than usual in summer

The usual seasonal pattern for LRTI hospitalisations was disrupted in 2020 and 2021 while the country managed the COVID-19 pandemic. The winter peak was near usual levels in 2022 and 2023, but summer 2022/23 hospitalisations were higher than prior to the pandemic (Figure 2). 

Figure 2: Number of lower respiratory tract infection hospitalisations in children aged 0–4 years, by month, 2018–2023

Information about this data

Lower respiratory tract infection hospitalisations

Source: National Minimum Dataset, Ministry of Health

Definition: Acute and semi-acute hospitalisations with pneumonia (ICD-10AM J12–J16, J18), bronchitis (J20), bronchiolitis (J21) or unspecified acute lower respiratory tract infection (J22) as the primary diagnosis, for children aged 0–4 years.  Analyses excluded overseas visitors and transfers within and between hospitals. Rates have been presented per 100,000 children.