A Case-Control Study to Identify Environmental Risk Factors for Hand, Foot, and Mouth Disease Outbreaks in Beijing

Abstract

SUMMARY: A matched case-control study was conducted in Beijing to identify the relative importance of major environmental risk factors for outbreaks of hand, foot, and mouth disease (HFMD). A case was defined as a kindergarten class with at least 1 HFMD outbreak. As a control, a kindergarten class that did not experience an HFMD outbreak was used. To identify potential transmission factors, the control group was divided into 2 subgroups: a sporadic group and an HFMD-negative group. We collected data for 8 environmental factors and basic information of each class. The correlations between the suspected environmental factors and HFMD outbreaks were analyzed. Thirty outbreak classes, 19 sporadic classes, and 30 HFMD-negative classes were enrolled. Class grade, indoor solar radiation, and ultraviolet (UV) radiation revealed significant differences among the 3 groups. After controlling for other factors, UV radiation (adjusted b ＝ -0.42) and class grade (adjusted b ＝ -0.46) as protective factors and temperature (adjusted b ＝ 0.31) as a risk factor were significantly associated with the attack rate by multiple linear regression analysis. Logistic regression analysis showed that the probability of an HFMD outbreak in the lower grade was 6-fold greater than that in the higher grade ( P ＝ 0.0380, odds ratio ＝ 0.157, 95z confidence interval ＝ 0.027-0.903). We identified UV radiation and class grade as protective factors that were associated with the epidemic intensity in Beijing. However, more data is needed to evaluate the relationship between these factors and HFMD outbreaks.

Hand, Foot and Mouth Disease in Hong Kong: A Time-Series Analysis on Its Relationship with Weather

“…Several proposed factors, including pathogen infectivity outside the host, human behavior, and immune function fluctuations, are involved in the seasonal patterns of infectious diseases [ 31 ], and these factors could also be responsible for the relationship between meteorological variations and HFMD. Our findings are generally in line with studies from different regions of Asia [ 15 – 17 , 21 – 28 ]. Our study found a positive association between temperature and HFMD, with increasing trends for mean temperatures between 8°C and 20°C and above 25°C and a plateau between 20°C and 25°C.…”

“…Some vaccine-preventable infectious diseases, including Japanese encephalitis, yellow fever, influenza, rotavirus infection, hepatitis A virus infection and hepatitis B virus infection, were also found to be differentially influenced by ultraviolet radiation from the sun through modulating vector reproduction [ 40 ]. In addition, a preventive effect of indoor solar radiation on HFMD was presumed [ 21 ]. One plausible reason is that higher solar radiation could also cause temperatures at ground level in urban areas to be higher than temperatures measured at weather stations.…”

“…Several time series studies have found associations between HFMD and weather, but the results have been inconsistent [ 15 – 17 , 20 – 28 ]. For example, studies from Singapore, Hong Kong, Japan and Guangdong, Henan, Shandong and Beijing in China have reported a positive association between temperature and HFMD [ 15 – 17 , 21 , 22 , 27 , 28 ], whereas a negative association has also been found [ 24 ]. In addition, disparity in the strongest effect of temperature was revealed as well, with an inverse-U relationship by one study, with 23°C (74°F) as the temperature with the maximum morbidity [ 23 ], while another study from Southern China reported more HFMD cases were associated with both high and low same-day temperature [ 25 ].…”

Effects of Meteorological Parameters and PM10 on the Incidence of Hand, Foot, and Mouth Disease in Children in China

“…Several limitations of this study should be acknowledged. First, some major risk factors for HFMD disease including season, suburban, ultraviolet (UV) radiation, childhood aggregation, socio-economic status [ 34 ], as well as environmental factors such as temperature, PM 10 , and PM 2.5 should be considered together to adjust them in the models. We adjusted only the meteorological parameters and PM 10 in the model, which may have led to outcome bias, thus, the next step is to improve the statistical methods.…”

Epidemiological Research on Hand, Foot, and Mouth Disease in Mainland China

“…Several researchers found that the incidence of HFMD might be associated with some environmental factors [ 14 , 24 , 31 , 51 , 52 , 53 , 54 , 55 , 56 ]. After analysis of the epidemiological features of HFMD in Mainland China during 2008–2012, Xin et al [ 14 ] indicated that evident geographical differences existed in the seasonal patterns of the incidence of HFMD between northern and southern China, and these differences were in weak associations with some climatic factors.…”