7.1 Basic Situation

The monitoring scope and items of 2004 was the same as that of 2003, including the urban area of Chongqing, Wanzhou District and Fengdu County of Chongqing Municipality and Yichang City of Hubei Province. The total population covered by this year's monitoring was 486,894, 3,738 less than that of the previous year with the same gender ratio of 1.02:1 between male and female.

In 2004, the total number of health institutions at all levels within the monitoring areas was 310, down by 4 compared with that of 2003. The total number of hospital beds in these institutions was 3,625, a reduction of 91 beds compared with that of the previous year. The total number of public health workers in these institutions was 4,047, down by 260 people against that of 2003, this was mainly due to the migration of the Three Gorges Reservoir area.

7.2 Life Statistics

7.2.1 Birth and death

There were altogether 4,005 babies born within the monitoring areas in 2004, among which 2,098 were male and 1,907 female. The birth rate was 8.23‰, up by 7.16% over the previous year. The total number of death was 2,767, among them, 1,555 were male and 1,212 female. The mortality rate was 5.68‰, 4.45% lower than that of the previous year. The death rate of Chongqing Municipality had a slight rise while that of Yichang, Wanzhou and Fengdu dropped to different extents, all within the normal range. Infant mortality was 12.48‰, lower than the level of the previous year (14.34‰). The life expectancy of all monitoring sites was higher than the national average (71.4 years old in 2000) with that of Fengdu (72.53 years old) close to the national average.

7.2.2 Analysis of death cause

According to the ICD-9 disease classification standard, a comparison among cause of death, gender and mortality of the top 10 causes of death for different gender indicated that malignant tumor was the No. 1 killer for men while circulatory diseases was the No. 1 killer for women. The order of the top 5 causes of death was the same as that of 2003 as: circulatory diseases (28.51%), malignant tumor (24.07%), respiratory diseases (20.20%), injury and poisoning (11.31%) and digestive diseases (3.61%). The death toll resulting from these 5 diseases accounted for 87.70% of the total and they were major killers for dwellers in the Three Gorges Reservoir area. Compared with 2003, the death percentage of circulatory diseases and injury and poisoning had dropped to some extents while that of malignant tumor and respiratory diseases rose to certain degrees.

7.3 Diseases Monitoring

7.3.1 Infectious Diseases Monitoring

In 2004, a total number of 3,455 cases of infectious diseases were reported from all the monitoring sites with the total morbidity of 709.60 per 100,000 people. No death case was reported. Among them, 2,481 cases of 12 types of Class B infectious diseases were reported with the morbidity of 509.56 in every 100,000 people. 974 cases of 5 types were identified as Class C infectious disease, and the incidence was 200.04 in every 100,000 people. There was no report on the case of Class A infectious disease. Respiratory diseases, blood and sexually transmitted diseases, digestive diseases and natural epidemic focus-based diseases took up 38.21%, 36.12%, 24.78% and 0.09% of the total cases respectively. Compared with that of the previous year, respiratory diseases rose to the top position, blood and sexually transmitted diseases rose to the second and digestive diseases dropped to the third. There were only cases of encephalitis B in the category of natural epidemic focus-based diseases with its percentage having no apparent change compared with that of 2003. Regarding the types of all infectious diseases, whooping cough disappeared while HIV Aids was added to the list. The incidences of 4 Class B infectious diseases of dysentery, typhoid fever, measles and scarlet fever saw certain degree of reduction, while the rest rose to different extents.

Compared with 2003, the top 5 types of Class B infectious diseases were somewhat different. They were viral hepatitis (205.18 in every 100,000), TB (187.93 in every 100,000), gonorrhea (53.81 in every 100,000), dysentery (45.80 in every 100,000) and syphilis (9.24 in every 100,000) respectively. The incidence of Class A and Class B infectious diseases grew by 38.74% in contrast to that of the previous year and reached the peak during the past 5 years. However, the reported incidence of Class C infectious diseases dropped by 9.79%. Among Class B infectious diseases, the incidence of hepatitis B and TB increased remarkably to 173.96/100,000 and 187.93/100,000, up by 142.69% and 28.95% respectively compared with that of 2003.

7.3.2 Endemic Diseases Monitoring

The monitoring results of endemic diseases of 2004 showed that the incidence of hypertrophy of the thyroid gland was the highest in Fengdu (11.88%) among the 4 monitoring sites while Yichang was the lowest of 3.33%. The incidence of hypertrophy of the thyroid gland among children aged 8 to 10 in Chongqing and Wanzhou was 9.89% and 6.88%, both lower than the sample survey results at each monitoring site in the same period last year. At all monitoring sites, the average coverage rate of iodized salt was 97.42% with 92.67% iodized salt products meeting national quality standard. And 89.99% of the local population under monitoring consumed qualified iodized salt. The up-to-standard rate and consumption rate of iodized salt of 2004 decreased by 6.03% and 5.95% respectively compared with that of the previous year. However, 50.55% of the subjects in Fengjie County of Chongqing Municipality showed positive testing results in endemic fluorine poisoning tests, a phenomenon deserving the attention of the local authorities.

7.4 Biological Medium Monitoring

The indoor mouse density was 1.61% in 2004, a little higher than that of 2003, but much lower than the average level of the 5 years before water impoundment (3.94%). The mouse density in spring was higher than that in autumn. The outdoor mouse density was 2.69%, lower than that of the previous year as well as the average level of the 5 years before water impoundment (4.22%). The outdoor mouse density was higher in autumn than in spring. Mouse density had a dramatic reduction after water impoundment into the Three Gorges Reservoir, which was possibly due to the all-round mice killing campaigns in the area before impoundment.

Sewer rat dominated the indoor mouse species, accounting for 55.71% of the total. Small house mouse (Mus musculus) ranked the second and took up 32.86%. In outdoor environment, small beast of insectivore (mainly short-tailed shrew) still dominated all other species and accounted for 65.67% of the total. Sewer rat (18.41%) was the second and black strip rat (7.96%) the third. There were not many small house mice and buff-breasted mouse, each accounting for less than 4%. Black strip rat was the host animal for epidemic haemorrhagic fever virus and leptospirosis, its percentage dropped from 14.35% of 2003 to 7.96% in 2004, continuously maintaining on a low level. Among all monitoring sites, Wanzhou had the highest indoor mouse density of 4.49% while Chongqing City had the lowest density of 0.86%. As for outdoor mouse density, Fengdu was the highest of 7.80% while Chongqing City was the lowest at 1.91%.

In 2004, all monitoring sites carried out relevant tests on lung (469) and kidney (488) samples of mice to identify the infection situation of epidemic haemorrhagic fever virus and leptospirosis. The findings showed that all samples were negative except two showing positive results on leptospirosis in Chongqing and two positives on epidemic haemorrhagic fever virus in Fengdu.

In the year 2004, the adult mosquito density in livestock pen of all monitoring sites was much higher than that of indoor. The overall adult mosquito density in livestock pen was 132.76/(pen·artificial hour), lower than 148.11/(pen·artificial hour) of 2003 or the average level of the 5 years before impoundment [198.57/(pen·artificial hour)]. The overall indoor adult mosquito density was 36.82/(pen·artificial hour), lower than the level of 43.09/(pen·artificial hour) of the previous year or the average level of the 5 years before impoundment [63.97/(pen·artificial hour)]. The change trend of mosquito density of both residential buildings and livestock pens in every ten days from May to September was the same. The adult mosquito density peak was generally in the trend of moving from the head to the tail of the reservoir. The mosquito density in residential buildings was the highest in Chongqing Municipality and lowest in Yichang. On the contrary, the mosquito density in livestock pens was the highest in Yichang and the lowest in Chongqing. The underlying reasons for the dramatic rise of mosquito density in livestock pens of Yichang in 2004 need further study.

Regarding the composition of mosquito species, Desvoidea obturbans dominated all the species in both residential buildings and livestock pens, accounting for 52.91% and 55.67% of the total number respectively. Similar to the previous year, the No.2 species of mosquito was culex pipiens fatigans, accounting for 23.66% in residential buildings and 17.47% in livestock pens.

7.5 Public Health of the Migration Resettlement Area

In 2004, public health monitoring work was conducted in 15 districts (counties) involving migration resettlement, which were under the administration of Chongqing Municipality. They included Wushan County, Wuxi County, Fengjie County, Yunyang County, Wanzhou District, Kaixian County, Zhongxian County, Shizhu County, Fengdu County, Wulong County, Fuling District, Changshou District, Banan District, Yubei District and Jiangjin City.

7.5.1 Life statistics

The total population in the monitoring area was 2,714,031 (including 1,350,907 in the resettlement area and 1,363,124 in the submerged area) in 2004. Among them, 1,398,424 were male and 1,315,607 female. 553,312 people were aged 0~14 while 243,094 were over 65, accounting for 20.39% and 8.96% of the total respectively.

A total of 22,313 babies were born in 2004 within the monitoring area with the birth rate of 8.22‰, 11,659 of which were male and 10,654 were female. Altogether 12,615 people died with the mortality of 464.81/100,000. Among the dead, 7,137 were male and 5,478 female. The total death in the resettlement area was 5,689 with the mortality of 508.10/100,000. In the submerged area, 6,926 people died with the mortality of 421.12/100,000.

7.5.2 Diseases monitoring

● Infectious diseases monitoring

In 2004, there were 10,466 cases of 16 types of Class B infectious diseases at all the monitoring sites with 1 case of death. The incidence of infectious diseases was 385.63/100,000 with mortality of 0.10‰. There were 2,498 cases of 6 types of Class C infectious diseases with the morbidity of 92.04/100,000. There was no outbreak of any epidemic diseases throughout the whole year. There were 5,921 cases of Class B infectious diseases in the resettlement area with morbidity of 438.30/100,000. In addition, 1,275 cases of Class C infectious diseases were reported with morbidity of 94.38/100,000. In the submerged area, 4,545 cases of Class B infectious diseases occurred with morbidity of 333.43/100,000. 1,223 cases of Class C infectious diseases occurred in 2004 with morbidity of 89.22/100,000.

In all kinds of infectious diseases, the order was as the followings: there were 1,397 cases of intestinal infectious disease, accounting for 13.35% with morbidity of 51.47/100,000; 4,086 cases of respiratory infectious diseases accounting for 39.04% with morbidity of 150.55/100,000; 4,927 cases of blood and sexually transmitted diseases accounting for 47.08% with morbidity of 181.54/100,000; 53 cases of insect-borne and natural epidemic focus-based (including 5 cases of haemorrhagic fever, 47 cases of encephalitis B and 1 case of diarrhea) diseases accounting for 0.50% with the incidence of 1.95 in every 100,000; and 3 cases of tetanus in newly-born babies accounting for 0.03% with the incidence of 0.11/100,000.

The monthly incidence of 30~40/100,000 for Class B infectious diseases occurred from May to September and from November to December. In January to April, the monthly morbidity of Class B infectious diseases was 20~30/100,000. For Class C infectious diseases, only March saw the monthly incidence of over 10/100,000 while all other months had monthly morbidity under 10/100,000.

There were 18 occupations reported cases of disease in 2004. The top 5 groups of people in terms of the largest number of cases were: farmer (4,752 cases, accounting for 36.66%), student (2,121 cases, accounting for 16.36%), worker (1,227 cases, accounting for 9.46%), people dealing with housework or unemployed (928 cases, accounting for 7.16%) and children living in scattered areas (651 cases, accounting for 5.02%).

● Endemic diseases monitoring

The monitoring work of endemic diseases included endemic fluorine poisoning, iodine-deficiency, endemic hypertrophy of the thyroid gland, malaria and paragonimiasis. Three districts (counties) of Wushan, Shizhu and Fuling carried out the investigation of endemic fluorine poisoning with 36,195 people having been tested and 7 were positive, the positive rate was 0.02%. As for iodine-deficiency, 1,161 people in 5 districts (counties) of Fengjie, Wanzhou, Zhongxian, Fengdu and Wulong were tested and 145 were reported positive with the rate of 12.49%. With regards to endemic hypertrophy of the thyroid gland, 37,100 people in 4 districts (counties) of Wushan, Kaixian, Shizhu and Fuling were tested and 59 were reported positive with the rate of 0.16%. As for malaria, 10,164 people from 10 districts (counties) including Wushan, Fengjie, Yunyang, Kaixian, Zhongxian, Wanzhou, Fengdu, Wulong, Fuling and Ba’nan were tested, and 1 was reported positive with the rate of 0.01%. For paragonimiasis, 36,504 people from 2 districts (counties) including Shizhu and Fuling were tested with no positive cases found.

7.5.3 Biological medium monitoring

● Mouse density and plague monitoring

In 2004, mouse density was monitored in 12 districts (counties) such as Wushan, Fengjie, Yunyang, Kaixian, Wanzhou, Zhongxian, Shizhu, Wulong, Fengdu, Fuling, Yubei and Banan. A total of 73,854 rattraps were deployed with 70,621 in function. As a result, 1,365 mice were caught with the mouse density of 1.93%. To be specific, the indoor mouse density was 2.11% while the outdoor density was 1.80%.

Another work was carried out in 8 districts (counties) including Wushan, Fengjie, Yunyang, Kaixian, Wanzhou, Zhongxian, Fengdu and Fuling to monitor the plague situation. As a result, 3,427 live mice were caught, accomplishing 84.41% of the target. Mouse fleas were found in 102 mice. Blood serum tests on plague antibody were carried out on 3,019 mice and all the results showed negative.

● Mosquito density monitoring

The mosquito density of 9 districts (counties) including Wushan, Fengjie, Yunyang, Kaixian, Wanzhou, Zhongxian, Fengdu, Fuling and Yubei was monitored. 112,750 mosquitoes were caught in 4,640 houses or livestock pen/time with the density of 97.20/artificial?hour. In specific, the mosquito density of residential buildings was 47.19/ artificial?hour while that in the livestock pen was 147.21/ artificial hour.

Desvoidea obturbans dominated all the mosquito species, accounting for 77.22% of the total. Culex pipiens fatigans took the second place, taking up 12.49%, followed by Anopheles sinensis accounting for 7.45%, Culex tritaeniorhynchus accounting for 2.04%, Culex pipiens pallens accounting for 0.23%, Aedes albopictus accounting for 0.06% and other mosquitoes accounting for 0.51%. The mosquito density reached its peak in late July at 62.86/artificial·hour in residential buildings and 143.57/ artificial·hour in livestock pens. The mosquito density hit its bottom in early May at 26.38/ artificial hour in residential buildings and 58.22/ artificial hour in livestock pens.