The epidemiology of viral/aseptic meningitis in New Zealand children from 1991-2017: an observational study

Abstract

Background: Aseptic meningitis includes culture negative and viral meningitis. Aseptic meningitis contributes a burden on health care including from unnecessary antibiotic use and prolonged hospital stay to treat possible bacterial meningitis.1,2 However, rates of aseptic meningitis in New Zealand (NZ) have not previously been described. Aim: The aim of this study was to describe trends, over 27 years, in hospital admissions of children in NZ with aseptic meningitis. Methods: In this population based study hospital admission rates were described from 1 Jan, 1991 to 31 Dec, 2017 for aseptic meningitis causes in children aged <15 years using International Classification of Disease coding of discharge diagnosis. Variations in admissions by age, year, sex, ethnicity, District Health Board and NZ Deprivation quintile at diagnosis were analysed. Counts of cases were divided by corresponding resident populations to calculate incident rates with 95% binomial confidence intervals. Poisson regression models were used to calculate incident rate ratios with 95% confidence intervals. We also analysed changes in incidence rate of disease over time using joinpoint regression models. Results: There were 4899 hospitalisations (62% male) due to aseptic meningitis in NZ children. The rate in males was 1.57 times (95%CI 1.48‐1.67) higher than females. Most admissions were due to unspecified viral meningitis (69%) followed by enterovirus (27%). The rate of hospital admissions varied annually with a median of 18.6 (interquartile range 14.1, 23.3) admissions/100,000 children aged <15 years including two peaks in 2000 and 2001 which had rates of 41.3 (95%CI 33.2‐51.5) and 53.1 (46.6‐60.7) per 100,000 children <15 respectively. Rates differed by age with an interaction effect with time. Since 2002 rates have been increasing in children <5 years at a rate of 4.1%/year (95%CI 3.1%‐5.1%) with the largest increase in those <1 year at an estimated rate of 5.6%/year (4.4%‐6.9%). However, in children aged >5 years the rates have been declining. Children aged <15 years living in areas of higher deprivation had an increased rate of aseptic meningitis; those in quintile 5 (most deprived) had a rate that was 2.44 times (95%CI 2.16‐2.75) higher those living in quintile 1 (least deprived). In total response ethnicity comparison from 1991–2013 higher rates were found in children of Pacific and NZ Māori compared with NZ European ethnicity. In 2013, the rate in Pacific children was 32.5/100,000 (23.8‐44.3), and in NZ Māori was 19.9 (14.9‐26.5) compared with 16.6/100 000 (13.7‐20.0) NZ European children. The highest rates of aseptic meningitis occurred in the north of NZ with a trend for lower rates in the south. Conclusions: Hospitalisation rates for aseptic meningitis in NZ children have increased in children aged <5 years since 2002, most significantly in infants. This may have been caused by improved diagnostic capabilities with widespread use of PCR since the 1990s. Aseptic meningitis hospitalisation rates were higher in children from locations with higher deprivation, and higher among children identified as Pacific or NZ Māori. Causes of ethnic, socioeconomic and geographical variation in aseptic meningitis hospitalisations warrants further investigation