Original ResearchDaily temperature change in relation to the risk of childhood bacillary dysentery among different age groups and sexes in a temperate city in China
Introduction
Bacillary dysentery (BD) is mainly caused by Shigella. Common clinical manifestations include fever, chills, abdominal pain and diarrhoea after an incubation period of one or two days.1 BD is mainly spread through the faecal–oral route and person-to-person contacts. BD epidemics are common among overcrowded populations with poor sanitation. Previous studies have found that trends in BD transmission show significant seasonality, and its incidence peaks in summer and autumn.2, 3, 4
In recent decades, although the incidence of BD has declined considerably in developing countries,5 the considerable burden of BD is still a great public health concern in impoverished areas.6, 7, 8 Globally, BD remains an important cause of mortality among children aged <5 years, especially in China.8, 9 According to the National Notifiable Diseases of China, the number of cases of BD reached almost 0.19 million, with an incidence of 138.2 per million, in 2013 and approximately 85% of cases occur in summer and autumn.10, 11 The burden of childhood BD has been reported to be much greater than the burden of other age groups (>14 years),12, 13, 14 suggesting that research into childhood BD would be of more practical significance.
Many individual, social and environmental factors are associated with the occurrence of BD.15 In northeast China, Huang et al. found that climatic factors (including temperature, evaporation, precipitation and relative humidity) were positively correlated with cases of BD.11 Associations between mean and maximum temperatures and BD have also been observed in Taiwan.16 Available evidence strongly suggests that children are more susceptible to BD, while few studies to date have focused on assessing the impact of temperature on BD among children, and little is known about whether the relationship between temperature and childhood BD varies by age and sex.
The incidence of BD in China is high, which can be largely attributable to the extremely high population mobility and high population density. Adverse effects of mean temperature (MT) on BD may exist in different areas with various socio-economic statuses, population characteristics and weather conditions. As such, an eastern inland city of China (Hefei) was selected as the study site. This study attempted to address the following research issues using a Poisson generalized linear regression model combined with a distributed lag non-linear model (DLNM):17
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What is the relationship between daily MT and childhood BD?
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Which subgroups are more vulnerable to the effects of MT on BD?
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Is there a delayed effect of MT on childhood BD?
Section snippets
Setting
Hefei, the capital city of Anhui Province, is located in the east of China (31°52′ N, 117°17′ E) (see Fig. 1). The city has an area of 11,408 km2, a population of approximately 7.61 million, and 18.1% of the population are aged 0–14 years.18 Hefei has a typical subtropical humid monsoon climate, with hot summers and mild winters.
Data collection
Daily data on BD morbidity in children (aged 0–14 years) between 2006 and 2012 were collected from Hefei Centre for Disease Control and Prevention. Age (0–5 years and
Results
Over the study period (2006–2012), 6511 cases of BD occurred in Hefei. Table 1 shows the summary statistics for childhood BD and climatic variables in the study area. There were 5560 cases of BD in children aged 0–5 years. The average number of daily BD cases was 5.1 (range 0–15). The average values for maximum, mean and minimum temperature were 21.3 °C (range −1.8–38.8 °C), 16.7 °C (range −5.1 °C–34.0 °C) and 13.0 °C (range −11.2–30.6 °C), respectively. The average values for RH and
Discussion
The purpose of this study was to investigate the relationship between MT and childhood BD. Several notable findings were observed. First, there was a significant relationship between MT and childhood BD, particularly in children aged 0–5 years, boys and girls. Second, the longest lagged effects of MT on BD differed between age and sex groups (lag of 7, 6, 3, 4 and 7 days for children aged 0–14 years, children aged 0–5 years, children aged 6–14 years, boys and girls, respectively). Third, the
Ethical approval
Ethical approval was obtained from the Ethic Review Board of Anhui Medical University.
Funding
This research was funded by Anhui Natural Science Fund (NO.1408085MH159).
Competing interests
None declared.
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