| BackgroundTropical cyclone usually generates in tropical or subtropical oceans, often accompanied by high winds, heavy rain and storm surge, which is a destructive extreme weather event. According to the Chinese national standard, tropical cyclones are categorized as tropical depression, tropical storm, severe tropical storm, typhoon, severe typhoon and super typhoon. China is one of the countries most affected by tropical cyclones in the world, about 7 tropical cyclones land in coastal areas in China every year. Among its coastal areas, Guangdong province is the most vulnerable to tropical cyclones with an average of three occurances each year. Under the background of global warming, the frequency and intensity of tropical cyclones is expected to increase, accompanied by high velocity and heavy precipitation.Not only are large number of casualties and economic losses associated with tropical cyclones landings, but also it has adverse effects on infectious diseases, chronic non-communicable diseases and psychological diseases. Tropical cyclone itself does not cause infectious diseases, but it increases the exposure to adverse environment, which then increases infection risk. Many prior researches indicated that tropical cyclones increased cases of some respiratory, gastrointestinal and vector-borne infectious diseases.In recent years, more and more national studies have been conducted about the impacts of climate change on human health, but very few of these studies focus on estimating the relationship between extreme weather events (such as flooding, drought and tropical cyclones) and infectious diseases.So far, there are 39 notifiable infectious diseases in China, consisting of:2 ’category A’infectious diseases,26’category B’infectious diseases and 11’category C infectious diseases. The morbidity of some infectious diseases and its’epidemiology areas increased, moreover, the frequency and intensity of tropical cyclones is expected to increase, therefore it is urgent to conduct studies on relationship between tropical cyclones and infectious diseases. Though varicella is not the national notifiable infectious disease, its morbidity in Guangdong province showed linear increase trend, In order to identify the sensitive infectious diseases of tropical cyclones and analyze its epidemiologic characteristics, our study selected Guangdong province as the study area and organized the surveillance case report data of 39 notifiable infectious diseases and varicella, which were obtained from the National Notifiable Disease Surveillance System (NDSS) of the Chinese Centers for Disease Control and Prevention (CDC). This analysis will be an important tool in providing basis for quantitative study about impacts of tropical cyclones and meteorological factors on sensitive infectious diseases.Objectives1. Identify sensitive infectious diseases of tropical cyclones from thirty-nine notifiable infectious diseases and varicella.2. Analyze epidemiologic characteristics of sensitive infectious diseases during typhoon period in landfall areas of tropical cyclones of Guangdong province.3. Quantitatively study the impacts of different categories of tropical cyclones and its’delay effects on sensitive infectious diseases in landfall areas of Guangdong province.MethodsOrganize the weekly data of 39 notifiable infectious diseases and varicella five weeks before and after tropical cyclones landed in Guangdong province during 2005-2011, and identify the sensitive infectious diseases of tropical cyclones in Guangdong province, tropical cyclones affected areas and landfall areas using Mann-Whitney U test. Description epidemiology method and drawing diseases grade distribution figure were applied to analyze the epidemiological characteristics of sensitive infectious diseases.1:1 uni-directional retrospective case-crossover designs were used to quantitatively estimate the relationship and delayed effects between different categories of tropical cyclones and sensitive infectious diseases in landfall areas. Software used in the statistical analysis included SPSS 21.0, ArcGIS 10.2.2 and SAS 9.2.Results1. Nineteen tropical cyclones landed in Guangdong province from 2005 to 2011, three tropical depressions, seven tropical storms, three severe tropical storms, five typhoons and one severe typhoon were included. Among them, there nine landed in the west, seven in the middle and three tropical cyclones, landed in the eastern coastal areas of Guangdong province, respectively. Most of these tropical cyclones landed from June to August.2. No new cases of category A infectious diseases were reported during typhoon period in Guangdong from 2005-2011, incidence of category B infectious diseases showed linear downward trend (Z=-20.59, P<0.001), incidence of category C infectious diseases yielded a linear upward trend (Z=635.54, P<0.001) and its’ incidence were higher than category B infectious diseases after 2009. Incidences of viral hepatitis, tuberculosis, sexually transmitted diseases, typhoid, paratyphoid, dysentery and measles among category B and influenza, mumps, other infectious diarrhea and hand-foot-mouth disease among category C were higher than others. Morbidity of varicella showed linear increase in Guangdong province.3. Study results of Mann-Whitney U test showed that measles, rubella, mumps, epidemic encephalitis B, hand-foot-mouth disease, other infectious diarrhea and varicella were sensitive infectious diseases in Guangdong province and other tropical cyclone affected areas. Among them, other infectious diarrhea and hand-foot-mouth disease were also sensitive infectious diseases in landfall areas of tropical cyclones.4. The incidence of other infectious diarrhea was on the rise with peak in October during typhoon season in Guangdong from 2005-2011. Morbidity in males was higher than in females, and lower age group especially 0-5 years old group was the high-risk population of other infectious diarrhea. Cases were reported in each of the 21 cities of Guangdong province, presented with distribution trend expanding from pearl-river delta region to other region of Guangdong, and the incidence of Jiangmen city was the highest.5. The incidence of hand-foot-mouth disease significantly increased during typhoon season in Guangdong province from 2008-2011, with a high wave shown in May to July. Similar with other infectious diarrhea, male incidence was also higher than that of female and lower than five years old were also its’high risk population. The spatial distribution of HFMD incidence expanded rapidly during the four years presented with higher incidence in Zhaoqing, Guangzhou, Foshan, Zhongshan and Zhuhai and gradually decreased toward other surrounding cities.6. Each grade of tropical cyclones could increase the risk of other infectious diarrhea among total population and high-risk population in landfall areas of Guangdong province during 2005-2011. The largest impacts of tropical depression, tropical storm, severe tropical storm and typhoon on other infectious diarrhea among total population were 1.95(5%CI:1.22-3.12) on lag 1 days,2.16(95%CI:1.69-2.76), 2.43 (95%CI:1.65-3.58) and 2.21 (95% CI:1.65-2.96) on lag 0 day, respectively. Among high-risk population, the largest OR and 95% CI of different grades tropical cyclones on other infectious diarrhea were all shown on lag 0 day with 2.67(1.10-6.48), 2.49(1.80-3.44),4.18(2.37-7.37) and 3.18(2.10-4.81), respectively.7. During 2008-2011, there was no statistical significance for the impacts of tropical depression on HFMD on lag 0-7 days among total population and high-risk population. Tropical storms had the largest impacts on HFMD among total population and high-risk population with OR=1.87 (95%CI:1.56-2.24) on lag 0 day and OR=2.46 (95%CI:2.13-2.84) on lag 7 days, respectively. The impacts of severe tropical storms and higher grade of tropical cyclones on HFMD were shown the largest OR (95%CI) on lagO (OR=2.54,95%:1.85-3.49) and lag 3 days (OR=2.52,95%:2.04-3.13), respectively.Conclusions 1. The onset of infectious diseases were related to tropical cyclones landfall, and sensitive infectious diseases of tropical cyclones included measles, rubella, mump, other infectious diarrhea, hand-foot-mouth disease and varicella. Hence, prevention and control work for these infectious diseases should be well done before tropical cyclones landfall in order to reduce corresponding disease burden.2. Incidences of other infectious diarrhea and HFMD in typhoon season were on the rise during 2005-2011 in Guangdong province, and their peaks were shown in October and May to July, respectively.0-5 years old were their high risk population and spatial distribution of the two infectious diseases showed expanding trend.3. Each grade of tropical cyclones could increase the onset risk of other infectious diarrhea; especially the impacts of severe tropical storm.. The impacts on high-at-risk population higher than that on general population. So making policies on prevention and control measures for post-disaster infectious diseases should be more target population oriented.4. Tropical depression had no effect on HFMD, the impacts of severe tropical storms and higher grade were larger than tropical storms. Tropical storms had larger effects on HFMD high-at-risk populations than that of total population, severe tropical storm and higher grade of tropical cyclones had lagged effects on high risk population.5. Except for tropical cyclones influences on the onset of other infectious diarrhea and HFMD; heavy precipitation, strong velocity, high humidity and vapor pressure, low pressure and short sunshine were also important risk factors. |
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