Impacts Of Tropical Cyclones On Hand, Foot And Mouth Disease In Guangdong, Fujian And Hainan Provinces, 2008-2013

BackgroundTropical cyclone (TC) is cyclone vortex which usually occurs in tropical and subtropical oceans, and is a powerful and profound tropical weather system. Due to the special geographical location, the coastal areas of China will be more or less affected by typhoon cyclone in summer and autumn. There are about 6.9 tropical cyclones landing in China annually in average. Guangdong Province is most frequently affected by tropical Cyclones, followed by Hainan Province, Taiwan Province and FujianProvince.Tropical cyclone brings about calamities as well as benefits. For example, it brings abundant fresh water for people and maintains a seasonal and climatic balance. However, it is still one of the world’s most serious natural disasters. Today, with global warming, the frequency and intensity of tropical cyclones are increasing accompanying wind speed and precipitation also demonstrates an increasing trend.Tropical cyclone not only can lead to a large number of casualties and economic loss but also can increase the risk of infectious diseases, chronic non-communicable diseases and psychological diseases. Tropical cyclones would change the environment for some microorganisms and insects, resulting in the migration of them thus cause outbreaks of infectious diseases. Researches have found that tropical cyclone will increase the risk of certain infectious diseases such as typhoid and paratyphoid fever, hepatitis, gastroenteritis, measles, leptospirosis, melioidosis, other infectious diarrhea and so on.The first outbreak of hand, foot and mouth disease (HFMD) was in Fuyang City of Anhui Province in 2008. Since then HFMD was reported as "category C" in the National Notifiable Disease Reporting System. HFMD is mainly caused by human enterovirus 71 and Coxsackie 16 virus. In recent years, an outbreak of HFMD caused by Coxsackie virus A6 was found both in China and other countries. HFMD mainly affects children under the age of 5 by causing herpes on hand, foot, mouth and hip. Severe patients may have complications, such as aseptic meningitis, encephalitis, acute flaccid paralysis, respiratory infections and myocarditis. Some patients have rapid progression and can die. There have been many studies about the influencing factors of HFMD, including age, history of exposure, disease severity, meteorological factors and so on. But there are few quantitative studies about the relationship between HFMD and tropical cyclones in China.We choose Guangdong province, Fujian province and Hainan province as the study areas and quantitatively explore the relationship between tropical cyelones and HFMD in landing cities, from 2008 to 2013.Objectives1. To analyze epidemiologic characteristics of hand, foot and mouth diseases in Guangdong, Fujian and Hainan provinces, from 2008 to 2013.2. To quantitatively examine the relationship and lagged effects between tropical cyclones and hand, foot and mouth diseases in landing cities, from 2008 to 2013.Methods1. Data about landfall tropical cyclones were collected from The Year Book of Tropical Cyclone and Chinese Typhoon website (http://112.124.12.97:8080/Typhoon/public/indexhtml) and whereas about hand, foot and mouth diseases from Chinese Center for Disease Control and Prevention from 2008 to 2013. Demographic information about the population in the three procvinces was retrieved from yearbooks and Chinese Center for Disease Control and Prevention. Descriptive analysis including incidence calculation and mapping were conducted to describe the epidemiological characteristics of hand, foot and mouth diseases in these three provinces.2. Symmetric 1:3 bidirectional case-crossover designs were used to quantitatively examine the relationship and delayed effects between different categories of tropical cyclones and hand, foot and mouth diseases. The principal component analysis was used to extract the principal components to solve the problem of multico linearity among meteorological factors. The extracted principal components were included in the regression model. Symmetric 1:3 bidirectional case-crossover design is similar to the matched case control design, so the conditional Logistic regression was used to build the regression model. Because of overlap bias, we took the matched factors as the strata and use the stratified Cox regression model to fit the model. All statistical analyses were performed using ArcGIS 10.2 and SAS 9.2.Results1. There were totally 21,15 and 11 tropical cyclones landing in Guangdong, Fujian and Hainan provinces from 2008 to 2013, respectively and most of them landed from June to August.2. The reported number of HFMD among males was more than that among females in these three provinces. Most cases were under 5 years old, and most of them are scattered children. The number of severe cases increased first and then decreased.3. This study indicates that there were two peaks of HFMD in these three provinces between 2008 and 2013. One peak was usually from April to July and the other one was from September to October. The declining point was usually in August. The main peak was in April to July in Guangdong and Fujian province, and September to October in Hainan province.4. The incidence of hand, foot and mouth diseases is mainly concentrated in the Pearl River Delta region of Guangdong Province. It is mainly concentrated in Ningde city, Fuzhou city, Quanzhou city and Zhangzhou city of Fujian province. The high-prevalence areas were in accordance with tropical cyclones landing cities in Fujian province. The high-prevalence areas were distributed in northeast and south Hainan province, and the low-prevalence areas were in the center of Hainan province.5. The landfall of Tropical storm could increase the risk of HFMD in different groups in Guangdong, Fujian and Hainan Province. The largest HR was on lag 7,10, 2 day in all groups of Guangdong, Fujian and Hainan province respectively. The impact of tropical storm on high-risk population was higher than total population in these three provinces and boys under 5 years old was higher than girls under 5 years old in both Guangdong and Hainan province. The impact was opposite in Fujian province.6. Severe tropical storm also increased the risk of HFMD in different groups in these three provinces. The largest HR was on lag 7 day in all groups of Guangdong and Fujian province. Severe tropical storm had the largest impact on lag 0,0,0,1 day in total population, high-risk population, boys under 5 years old and girls under 5 years old. The impact of severe tropical storm on high-risk population was higher than total population and boys under 5 years old higher than girls under 5 years old in these three provinces.7. Typhoon increased the risk of HFMD in different groups in Guangdong and Hainan province. The largest HR was on lag 7,7,7 and 0 day in total population, high-risk population, boys under 5 years old and girls under 5 years old in Guangdong province. The largest HR was all on lag 2 day in different groups in Hainan province. Typhoon increased the risk of HFMD on lag 0-3 days and decreased on lag 4-10 days. The largest decrease was on lag 10 day. The impact of typhoon on high-risk population was higher than total population and boys under 5 years old lower than girls under 5 years old in these three provinces.8. Severe typhoon could increase the risk of HFMD in different groups in Guangdong province. The largest HR was all on lag 7 day. The impact of severe typhoon on high-risk population was higher than total population and boys under 5 years old lower than girls under 5 years old in Guangdong province. Severe typhoon may decrease the risk of HFMD in different groups in Fujian province. But there were no statistical significance on most lag days. So this study could not make sure the impact of severe typhoon in Fujian province. Severe typhoon increased the risk of HFMD on lag 0-4 days and decreased on lag 5-10 days. The largest decrease was on lag 10 day.9. In Guangdong province, the impact of different grades of tropical cyclones on HFMD among total population, high-risk population and girls under 5 years old were different:tropical storm had higher impact than severe typhoon, followed by severe tropical storm and typhoon. For boys under 5 years old, the rank was:tropical storm, severe tropical storm, severe typhoon and typhoon. In Fujian province, the impact of different grades of tropical cyclones on HFMD among total population and high-risk population were also different:severe tropical storm had larger impact than typhoon, tropical storm and severe typhoon. For boys under 5 years old, the rank was: severe tropical storm, tropical storm, typhoon and severe typhoon. For girls under 5 years old, the rank was:severe tropical storm, tropical storm, severe typhoon and typhoon. In Hainan province, the rank of the impact of different grades of tropical cyclones on HFMD among all population was severe tropical storm, tropical storm, severe typhoon and typhoon.Conclusions1. The epidemiologic characters of HFMD were diverse among different areas. Therefore, the prevention and control measures should be taken according to local conditions.2. The landing of tropical cyclones increased the risk of hand, foot and mouth disease. So in the tropical cyclones landing, health education and health intervention should be done in daily life.3. The incidence rate of HFMD showed an increasing trend in Guangdong, Fujian, and Hainan provinces. Hand, foot and mouth diseases peaked annually in the late spring and early summer as well as late autumn and early winter. High risk groups were children under five years old. Scattered children accounted for the majority of reported cases.4. The influence and lagged effects of different grades of tropical cyclones on hand, foot and mouth disease were different among different regions. The influences on high-risk groups were higher than total population.