Factors influencing Hand-Foot-Mouth disease in the Mekong Delta Region in the Context of Climate Change and Potential Strategies to Improve Prevention and Control

Climate-sensitive infectious diseases such as hand-foot-mouth disease (HFMD) are expected to increase with the changing climate, leading to a greater burden on population health. The extent to which the changes in climate can or will affect population health varies across regions, depending on specific climate characteristics and variability, and on the specific socio-economic and health infrastructure of each region. Hence, local regional-specific climate change adaptation measures needed to be based on an understanding of the health impacts at the regional level. This is particularly relevant when dealing with the hand-foot-mouth disease (HFMD). HFMD, caused by a group of enteroviruses, mainly EV71 and CVA16, is an emerging and increasingly wide spread climate-sensitive infectious disease. It has become endemic over recent decades in many countries, especially in the Western Pacific Region including China, Japan, Singapore and Vietnam. Millions of children suffer from this disease every year, and in severe cases, it is fatal. Research has focused on clinical diagnosis, testing, and treatment in order to reduce mortality. Few studies have investigated prevention and control of HFMD. Recent studies have begun to examine the relationship between HFMD and climate factors such as temperature, humidity, and rainfall. These studies also report that there are regional variations associated with differences in socio-economic characteristics, geographic and climate zones. Thus, regional research is needed to better understand the specific climate-HFMD associations, especially in the “high-risk” regions vulnerable to climate change such as the Mekong Delta Region (MDR) in southern Vietnam. The MDR has been a focus of climate change research over the past decade. While studies have identified many climate change related issues such as increases in temperature and number of hot days, sea level rises and floods. However, only a few have examined the impacts of climate change on human health and none on prevention and control measures or climate change adaptation. In fact, health is not even included by Vietnam’s national climate change adaptation plan. Thus, research into climate change-sensitive infectious diseases such as the HFMD to demonstrate its increasing spread and adverse impacts and provide evidence-based recommendations for prevention and control is urgently needed. This study aimed to examine the influence of climate, socio-economic, and health-related factors on the distribution of HFMD, and to suggest strategies to improve HFMD prevention and control with a focus on the MDR. It used mixed methods to explore the status of HFMD in the MDR, investigated the multiple factors influencing it, its high-risk locations, and current methods to prevent and control it. It used quantitative methods, consisting of temporal analysis (time-series analysis) and spatial and space-time analysis, to examine the climate factors influencing HFMD, and to detect high-risk clusters of it in time and space. This was followed by the use of spatial autoregressive models to determine the potential influences of ten socio-economic and health-related factors on its distributions across all provinces of the MDR. Qualitative methods, including extensive literature and document reviews and in-depth interviews with 17 health staff at both provincial and national level, were used to understand their perspectives on the current situation of HFMD, existing prevention and control measures, and the support required by health staff in order to improve prevention and control, especially in the context of climate change. The study examined the associations between three climate factors, temperature, humidity, and rainfall, and the incidence of HFMD in the MDR for both daily and weekly analyses. The finding demonstrated statistically significant associations, especially for temperature and humidity. Specifically, a one-degree increase in temperature was associated with a 1.7% (95%CI, 0.1-3.3%) increase of HFMD at lag 0 day, and a one-percent increase in humidity was associated with a 0.3% (95%CI, 0.1-0.5%) increase in HFMD at lag 3 day. Furthermore, the strength of temperature-HFMD associations and humidity-HFMD associations both increase with week lags. Consequently, following increases in temperature projected for the MDR as a result of the changing climate, the number of HFMD cases is expected to increase in the region. Regarding spatial distribution of HFMD, this study identified four provinces with relatively higher risks: Long An, Dong Thap, Vinh Long, and Ben Tre provinces. They all share borders in the north of the MDR. Quantitative analysis also revealed high-risk time-space clusters, implying that for the high-risk time of year in the high-risk provinces, more attention should be paid to HFMD prevention and control. This study also found that two out of the ten socio-economic and health-related factors examined had strong modifying effects on the distribution of HFMD across the 13 provinces: the percentage of children under one year old having full vaccination (-7.13%; 95%CI, -12.9 - -1.33%) and the percentage of houses with access to safe water (-3.69%; 95%CI, -7.11- -0.27%). Further analysis of the modification effects of these two factors on climate-HFMD associations found different levels of association between the groups with higher/lower immunisation or higher/lower access to safe water. These findings provide evidence that socio-economic and health-related factors influence the incidence of HFMD. This suggests that future studies should focus on a comprehensive analysis of such factors in order to develop predictive models of HFMD. Through qualitative methods, this research has gained a better understanding of the current situation of HFMD and its prevention and control from the perspective of health staff at both the provincial and national levels, including their existing difficulties in implementing and sustaining prevention and control measures in their communities. The key challenges that health staff face include issues related to health risk communication with community members, the frequent overloading in hospitals in particular times and locations, the change in seasonal patterns of common infectious diseases, the lack of knowledge and awareness of climate change and its potential impacts on health in the region, and the weak collaboration between the health sector and the environmental sector in general. The key recommendation of this study are (1) the national climate change adaptation plan should include health sectors and strategies to reduce adverse climate change impacts on health, (2) the prevention and control plan of HFMD should focus more strongly on the identified high-risk areas and set up surveillance and information sharing across provinces (3) health authority should establish inter-provinces collaboration and health notification system to promptly notify other provinces of outbreak in order to prevent potential spread of HFMD , and (4) health staff should be provided with more information about how climate change affects health to enable them to develop more effective communication with community members and develop better plan for HFMD prevention and control. This study contributes to the scientific evidence base of the associations between HFMD and climate, and socio-economic factors with a focus on the MDR. It also presents the perspectives of health staff dealing with HFMD and their support needs in order to improve prevention and control. The study itself has already helped to raise health staff awareness of the potential impacts of climate change on health, in particular, infectious disease. The methods used in this study can be applied by other regions dealing with infectious diseases to provide convincing evidence of the relationship between climate change and health. Future studies should focus on translating research evidence into policies and practices to prevent and control HFMD tailored to address local/regional conditions, and to integrate health into climate change adaptation activities in Vietnam.