Background: Previous studies have always focused on the impact of various meteorological factors on Hand–foot– mouth disease (HFMD). However, only few studies have investigated the simultaneous effects of climate and air pollution on HFMD incidence. Methods: Daily HFMD counts among children aged 0–۱۴ years in Guilin city were collected from 2014 to 2016. Distributed lag nonlinear models (DLNM) were used to assess the effects of extreme meteorological factors and air pollution indicators, as well as the effects of different lag days on HFMD incidence. Furthermore, this study explored the variability across gender and age groups. Results: Extreme temperatures, high precipitation and low-O3 concentration increased the risk of HFMD. Hot effect was stronger and longer lasting than cold effect. Risks of rainy effect and low-O3 effect continued to increase as lag days extended, with the maximum RR values: 1.60 (1.38, 1.86) (90th vs median) and 1.48 (1.16, 1.89) (1th vs median) at 0–۱۴ lag days, respectively. By contrast, extremely high wind speed, low precipitation, low PM2.5 and high O3 exerted a certain protective effect on HFMD incidence. The corresponding minimum RR values were: 0.85 (0.74, 0.98) (90th vs median) at 0–۱۴ lag days, 0.98 (0.97, 0.99) (10th vs median) at 0–۱۴ lag days, 0.73 (0.61, 0.88) (1th vs median) at 0–۱۴ lag days and 0.81 (0.73, 0.90) (99th vs median) at 0–۷ lag days, respectively Male children and children aged 0–۱ years (followed by 1–۳ years) were the most susceptible subgroups to extreme climatic effects and air pollution. Conclusions: Our results indicated that daily meteorological factors and air pollution exert non-linear and delayed effects on pediatric HFMD, and such effects vary depending on gender and age. These findings may serve as a reference for the development of an early warning system and for the adoption of specific interventions for vulnerable groups.

Introduction

Hand–foot–mouth disease (HFMD) is an acute infectious disease caused by enteroviruses, such as human enterovirus 71 (EV-71) and Coxsackievirus A group 16(Ang et al., 2009). HFMD is prevalent among preschoolers, and severe cases are mostly caused by EV-71 infection. This disease is self-limiting and mainly spreads through fecal-oral transmission or through close contact. Although its typical clinical symptoms are mild (such as rashes on hands, feet, and hip, as well as oral mucosal herpes), it occasionally causes severe complications, such as meningitis and encephalitis, which may lead to death. No effective vaccines and specific antiviral therapies for HFMD have been developed (Mao et al., 2016). HFMD was first reported in New Zealand in 1957, and it has become an urgent issue in global public health (Zhuang et al., 2015). Frequent HFMD outbreaks were experienced in the Asia-Pacific region in the past decades. In the spring of 2008, a large, unprecedented HFMD outbreak was experienced in Fuyang City (China), wherein 6049 cases and 22 deaths were recorded (Yan et al., 2010). Large-scale HFMD outbreaks also occurred in South Korea and Hong Kong in 2009 and 2011, respectively (Lee et al., 2013; Song et al., 2015). Followed by vast HFMD cases and local outbreaks being observed in Vietnam and Thailand (Nguyen et al., 2014; Puenpa et al., 2014), as well as in Malaysia and India (Nmn et al., 2016; Palani et al., 2016). In addition, mainland China has been suffering from a huge burden caused by HFMD due to its large population base. The incidence of HFMD in 2014 was 203.16/100,000 and the mortality was 18.03/100,000, exceeding those in most East Asian countries (Zhuang et al., 2015). Hence, identification of the risk factors for HFMD and establishment of a targeted early warning system are crucial to the control of HFMD outbreak and reduction of the burden caused by this disease common among children.