The Seasonal Drivers of Hand, Foot, and Mouth Disease in ......The Seasonal Drivers of Hand, Foot,...
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The Seasonal Drivers of Hand, Foot, and Mouth Disease in Thailand Nathan Warriner, Kevin Bakker Abstract In recent years, Hand, Foot, and Mouth Disease (HFMD) has emerged as a serious public health issue in Thailand with nearly 80,000 cases in 2016 alone (1). This is nearly double the number of cases seen in the previous year. HFMD continues to be transmitted throughout Thailand without a conclusive explanation for its seasonal pattern. The main purpose of this study is to understand the seasonal dynamics of HFMD in Thailand, which will provide further insight into the epidemiology of the disease. Time series analyses indicated that HFMD exhibits a strong seasonal pattern across the entire country, with a significant peak in cases in July. Age structure analyses revealed that on average, 89.2% of cases occurred in children under 5 years and 57% of HFMD cases were found in children aged 1-2. Incidence rates from across the country demonstrated an increasing trend of HFMD in Thailand, with an extremely large number of cases reported in the last few years. References 1) Thai-Government. (2016) National Disease Surveillance.http://www.boe.moph.go.th/. Accessed June 12, 2016. 2) World Health Organization. (2011). A Guide to Clinical Management and Public Health Response for Hand, Foot and Mouth Disease (HFMD). Retrieved from http://www.wpro.who.int/emerging_diseases/documents/HFMDGuidance/en/ 3) Chen, Chun, Hualiang Lin, Xiaoquan Li, Lingling Lang, Xincai Xiao, Peng Ding, Peng He, Ying Zhang, Ming Wang, and Qiyong Liu. Short-term effects of meteorological factors on children hand, foot and mouth disease in Guangzhou, China. International Journal of Biometeorology. 2014; 58(7):1605- 1614. 4) Samphutthanon R, Tripathi NK, Ninsawat S, Duboz R. Spatio-Temporal Distribution and Hotspots of Hand, Foot and Mouth Disease (HFMD) in Northern Thailand. International Journal of Environmental Research and Public Health. 2014; 11(1):312-336. 5) Wang, Jin-feng and Guo, Yan-Sha and Christakos, George and Yang, Wei-Zhong and Liao, Yi-Lan and LI, Zhong-Jie and LI, Xiao-Zhou and Lai, Sheng-Jie and Chen, Hong-Yan. Hand, foot and mouth disease: spatiotemporal transmission and climate. International Journal of Health Geographics. 2011; 10(1):25. Next Steps Now that we have a full understanding of HFMD dynamics in Thailand, our next steps will link HFMD seasonality to environmental (temperature, rainfall, and humidity) and social (term-time forcing) covariates. Finally, we will build mechanistic models to fit current, and forecast future, cases of HFMD in Thailand. This work will identify which, if any, covariate is the primary driver of HFMD seasonality in Thailand. Background HFMD is particularly concerning because no available vaccine exists, most cases are seen in children under five years, and infection can cause permanent cardiac or neurological damage. Following several years of outbreaks, international meetings were held to develop surveillance systems and strategies for combating HFMD in Southeastern Asia and the Western Pacific (2). Previous studies have reported that positive correlations exist between the incidence of HMFD and environmental variables such as temperature, humidity (3,4), and rainfall (5). Methods Monthly HFMD cases and annual age structure data were digitized from the Thailand Ministry of Public Health website from the years 2003-2015 (1). The 76 Thai provinces of were divided into 19 zones (0-18, Fig. 1), with Bangkok representing zone 0. The 19 zones were further separated into one of four regions: Central, Southern, Northeast, and Northern, indicated by the red lines. Time series, general additive models, and incidence rates were created for each zone, region, and the entire country. GAM plots were constructed using data from 2010-2015, when cases became abundant. Age distribution was calculated for ages under 1 year, 1-2 years, 2-3 years, 3-4 years, 4-5 years, and over 5 years from 2003-2015. 15 16 17 10 11 18 4 2 14 12 13 3 9 1 5 0 7 6 8 Zones: 0-5, 9 = Central 6-8 = Southern 10-14 = Northeast 15-18 = Northern Thailand Results 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Age Distribution of HFMD in Thailand Year Percent of Infections 0.0 0.2 0.4 0.6 0.8 1.0 U1 1−2 2−3 3−4 4−5 O5 −400 −200 0 200 400 600 Month Variation from Mean Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec −400 −200 0 200 400 600 HFMD Seasonal Distribution: Zone 0−18 (2010−2015) Zone.0 Zone.1 Zone.2 Zone.3 Zone.4 Zone.5 Zone.6 Zone.7 Zone.8 Zone.9 Zone.10 Zone.11 Zone.12 Zone.13 Zone.14 Zone.15 Zone.16 Zone.17 Zone.18 0 500 1000 1500 2000 2500 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 0 500 1000 1500 2000 2500 Cases of HFMD in Thailand: Zone 0 − Zone 18 Year Cases (N) t 0 2000 4000 6000 8000 10000 12000 14000 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 0 2000 4000 6000 8000 10000 12000 14000 Total Cases of HFMD in Thailand Year Cases (N) 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 0 2 4 6 8 10 12 HFMD Incidence Rates in Thailand Year Rate per 10,000 General additive model (GAM) demonstrating the seasonality of HFMD in each zone. The number of cases seen in July is significantly different than other months. Zone 0 (Bangkok) is the blue curve exhibiting a strong seasonal pattern. HFMD time series of Thailand and each of the 19 zones. HFMD exhibits an increasing trend in cases and an annual peak midway through the year. HFMD incidence rates in all 19 zones. Zone 0, city of Bangkok and most populated zone, has the highest incidence rate of HFMD. Zone 14 is the second most populated zone and it displays the second highest incidence rate. Incidence rates of HFMD in Thailand from 2003-2015. The figure shows an overall rise in incidence rate of HFMD for the time period. Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Zone 0 Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9 Zone 10 Zone 11 Zone 12 Zone 13 Zone 14 Zone 15 Zone 16 Zone 17 Zone 18 0 2 4 6 8 10 HFMD Incidence Rates: Zone 0−18 (2010−2015) Location Rate per 10,000 Figure 6. Figure 7. Age distribution of HFMD in Thailand form 2003-2015. On average, 89.2% of all HFMD cases presented in children under the age of 5. The majority cases (57%) occurred in children aged 1-2.
Transcript of The Seasonal Drivers of Hand, Foot, and Mouth Disease in ......The Seasonal Drivers of Hand, Foot,...
The Seasonal Drivers of Hand, Foot, and Mouth Disease in ThailandNathan Warriner, Kevin Bakker
AbstractIn recent years, Hand, Foot, and Mouth Disease (HFMD) has emerged as a serious public health issue in Thailand with nearly 80,000 cases in 2016 alone (1). This is nearly double the number of cases seen in the previous year. HFMD continues to be transmitted throughout Thailand without a conclusive explanation for its seasonal pattern. The main purpose of this study is to understand the seasonal dynamics of HFMD in Thailand, which will provide further insight into the epidemiology of the disease. Time series analyses indicated that HFMD exhibits a strong seasonal pattern across the entire country, with a significant peak in cases in July. Age structure analyses revealed that on average, 89.2% of cases occurred in children under 5 years and 57% of HFMD cases were found in children aged 1-2. Incidence rates from across the country demonstrated an increasing trend of HFMD in Thailand, with an extremely large number of cases reported in the last few years.
References1) Thai-Government. (2016) National Disease Surveillance.http://www.boe.moph.go.th/. Accessed June 12, 2016.2) World Health Organization. (2011). A Guide to Clinical Management and Public Health Response for Hand, Foot and Mouth Disease (HFMD). Retrieved from http://www.wpro.who.int/emerging_diseases/documents/HFMDGuidance/en/3) Chen, Chun, Hualiang Lin, Xiaoquan Li, Lingling Lang, Xincai Xiao, Peng Ding, Peng He, Ying Zhang, Ming Wang, and Qiyong Liu. Short-term effects of meteorological factors on children hand, foot and mouth disease in Guangzhou, China. International Journal of Biometeorology. 2014; 58(7):1605-1614.4) Samphutthanon R, Tripathi NK, Ninsawat S, Duboz R. Spatio-Temporal Distribution and Hotspots of Hand, Foot and Mouth Disease (HFMD) in Northern Thailand. International Journal of Environmental Research and Public Health. 2014; 11(1):312-336.5) Wang, Jin-feng and Guo, Yan-Sha and Christakos, George and Yang, Wei-Zhong and Liao, Yi-Lan and LI, Zhong-Jie and LI, Xiao-Zhou and Lai, Sheng-Jie and Chen, Hong-Yan. Hand, foot and mouth disease: spatiotemporal transmission and climate. International Journal of Health Geographics. 2011; 10(1):25.
Next StepsNow that we have a full understanding of HFMD dynamics in Thailand, our next steps will link HFMD seasonality to environmental (temperature, rainfall, and humidity) and social (term-time forcing) covariates. Finally, we will build mechanistic models to fit current, and forecast future, cases of HFMD in Thailand. This work will identify which, if any, covariate is the primary driver of HFMD seasonality in Thailand.
BackgroundHFMD is particularly concerning because no available vaccine exists, most cases are seen in children under five years, and infection can cause permanent cardiac or neurological damage. Following several years of outbreaks, international meetings were held to develop surveillance systems and strategies for combating HFMD in Southeastern Asia and the Western Pacific (2). Previous studies have reported that positive correlations exist between the incidence of HMFD and environmental variables such as temperature, humidity (3,4), and rainfall (5).
MethodsMonthly HFMD cases and annual age structure data were digitized from the Thailand Ministry of Public Health website from the years 2003-2015 (1). The 76 Thai provinces of were divided into 19 zones (0-18, Fig. 1), with Bangkok representing zone 0. The 19 zones were further separated into one of four regions: Central, Southern, Northeast, and Northern, indicated by the red lines. Time series, general additive models, and incidence rates were created for each zone, region, and the entire country. GAM plots were constructed using data from 2010-2015, when cases became abundant. Age distribution was calculated for ages under 1 year, 1-2 years, 2-3 years, 3-4 years, 4-5 years, and over 5 years from 2003-2015.
15
16
17 10 11
18
4 2 14
12
13
3
9
1
5 0
7 6
8
Zones: 0-5, 9 = Central 6-8 = Southern 10-14 = Northeast 15-18 = Northern
Thailand
Results
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Age Distribution of HFMD in Thailand
Year
Perc
ent o
f Inf
ectio
ns
0.0
0.2
0.4
0.6
0.8
1.0
U11−22−33−44−5O5
−400
−200
020
040
060
0
Month
Varia
tion
from
Mea
n
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
−400
−200
020
040
060
0
HFMD Seasonal Distribution: Zone 0−18 (2010−2015)
Zone.0Zone.1Zone.2Zone.3Zone.4Zone.5Zone.6Zone.7Zone.8Zone.9
Zone.10Zone.11Zone.12Zone.13Zone.14Zone.15Zone.16Zone.17Zone.18
050
010
0015
0020
0025
00
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
050
010
0015
0020
0025
00
Cases of HFMD in Thailand: Zone 0 − Zone 18
Year
Cas
es (N
)
t
020
0040
0060
0080
0010
000
1200
014
000
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
020
0040
0060
0080
0010
000
1200
014
000
Total Cases of HFMD in Thailand
Year
Cas
es (N
)
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
02
46
810
12
HFMD Incidence Rates in Thailand
Year
Rat
e pe
r 10,
000
General additive model (GAM) demonstrating the seasonality of HFMD in each zone. The number of cases seen in July is significantly different than other months. Zone 0 (Bangkok) is the blue curve exhibiting a strong seasonal pattern.
HFMD time series of Thailand and each of the 19 zones. HFMD exhibits an increasing trend in cases and an annual peak midway through the year.
HFMD incidence rates in all 19 zones. Zone 0, city of Bangkok and most populated zone, has the highest incidence rate of HFMD. Zone 14 is the second most populated zone and it displays the second highest incidence rate.
Incidence rates of HFMD in Thailand from 2003-2015. The figure shows an overall rise in incidence rate of HFMD for the time period.
Figure 1.
Figure 2. Figure 3.
Figure 4.
Figure 5.
Zone 0 Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9 Zone 10 Zone 11 Zone 12 Zone 13 Zone 14 Zone 15 Zone 16 Zone 17 Zone 18
02
46
810
HFMD Incidence Rates: Zone 0−18 (2010−2015)
Location
Rat
e pe
r 10,
000
Figure 6.
Figure 7.
Age distribution of HFMD in Thailand form 2003-2015. On average, 89.2% of all HFMD cases presented in children under the age of 5. The majority cases (57%) occurred in children aged 1-2.
