Using interrupted time series design to analyze changes in hand, foot, and mouth disease incidence during the declining incidence periods of 2008-2010 in China.

OBJECTIVE: To identify patterns of hand, foot and mouth disease (HFMD) incidence in China during declining incidence periods of 2008, 2009, and 2010. METHODS: Reported HFMD cases over a period of 25 months were extracted from the National Disease Reporting System (NDRS) and analyzed. An interrupted time series (ITS) technique was used to detect changes in HFMD incidence rates in terms of level and slope between declining incidence periods of the three years. RESULTS: Over 3.58 million HFMD cases younger than 5 years were reported to the NDRS between May 1, 2008, and May 31, 2011. Males comprised 63.4% of the cases. ITS analyses demonstrated a significant increase in incidence rate level (P<0.0001) when comparing the current period with the previous period. There were significant changes in declining slopes when comparing 2010 to 2009, and 2010 to 2008 (all P<0.005), but not 2009 to 2008. CONCLUSION: Incremental changes in incidence rate level during the declining incidence periods of 2009 and 2010 can potentially be attributed to a few factors. The more steeply declining slope in 2010 compared with previous years could be ascribed to the implementation of more effective interventions and preventive strategies in 2010. Further investigation is required to examine this possibility.

Prenatal exposure to perfluoroalkyl substances is associated with lower hand, foot and mouth disease viruses antibody response in infancy: Findings from the Guangzhou Birth Cohort Study.

BACKGROUND: Perfluoroalkyl substances (PFASs) are synthetic chemicals widely used in industry and for commercial products. Their immunomodulatory effects are a growing health concern in children. Hand, Foot and Mouth Disease (HFMD) is a common childhood viral infection, and increased incidence of which has parallel the rise in PFAS exposure in the Asia-Pacific region. OBJECTIVE: We conducted the first study to assess whether prenatal exposure to PFAS was associated with a reduction in HFMD virus antibodies in infants. METHODS: We enrolled 201 mother-infant pairs from the Guangzhou Birth Cohort Study from July to October 2013. High performance liquid chromatography-mass spectrometry was employed to determine concentrations of specific PFAS isomers in cord blood. Neutralizing antibodies titers were measured against two HFMD viruses, enterovirus 71 (EV71) and coxsackievirus A 16 (CA16), in cord blood serum and blood serum at three months of age. RESULTS: Higher umbilical cord blood PFAS concentrations were associated with lower EV71 and CA16 antibody concentrations. A doubling in the composite sum of cord blood PFASs in three month old infants was associated with significant increase in the risk of HFMD antibody concentration below clinical protection level (≥1:8 titers) for CA16 (odds ratio, OR: 2.74 [95% confidence interval (CI): 1.33, 5.61] and for EV71 (OR = 4.55, 95% CI: 1.45, 4.28). This association was higher in boys at three months of age for CA16. CONCLUSIONS: Our findings suggest that cord blood PFAS exposure is associated with lower HFMD antibody in infancy. Given the widespread nature of PFAS exposures and the high global incidence of HFMD globally, these findings have substantial public health implications and therefore, these associations need to be replicated in a larger study to more definitively address the risk.

[Spatial clustering and changing trend of hand-foot-mouth disease during 2008-2011 in China].

OBJECTIVE: The purpose of this study was to explore the spatial clustering, specific clustering areas, as well as changing trend of clustering areas of hand-foot-mouth disease (HFMD). METHODS: Exploratory spatial data analysis (ESDA) was used to conduct spatial statistical analyses for the HFMD using 2008 - 2011 data at both provincial and county/district levels. RESULTS: The Global Moran's I coefficients appeared to be 0.3336, 0.6074, 0.3372, 0.4620 and 0.4367 for 2008 - 2011 and for the combined 4 years, respectively. The corresponding P-values were 0.002, 0.001, 0.004, 0.001 and 0.001 respectively, when using the Monte Carlo tests with all the P-values less than 0.05. Moran's I coefficients ranged between 0.3 and 0.7, showing the appearance of moderate or higher clustering nature. Based on the results from nationwide analyses on clustering areas at the county/district levels between 2008 and 2011 (Moran's I = 0.5198, P = 0.001), it appeared a moderate clustering nature. When local autocorrelation analysis was applied at the provincial level, 3 hot spot areas in Beijing, Tianjin and Shanghai cities in 2008; 7 hot spot areas in Beijing, Tianjin, Hebei, Shanxi, Shanghai, Jiangsu and Shandong in 2009; four hot spot areas: Beijing, Tianjin, Guangdong and Guangxi; five hot spot areas: Fujian, Jiangxi, Hunan, Guangdong and Guangxi in 2011, were discovered. 390 hot-spot counties/districts were found through local autocorrelation analyses using the three-year data of 2008 to 2010. CONCLUSION: Spatial clustering nature of HFMD incidence between 2008 and 2011 in China appeared to be moderate or high, with the clustered areas a north to south shifting trend. However, further investigation was in need to address this changing trend.