7.1 Basic Situatio

The monitoring scope and the layout of monitoring stations of 2005 was the same as that of the previous year, including the urban area of Chongqing, Wanzhou District and Fengdu County of Chongqing Municipality and Yichang City of Hubei Province. The total population under the monitoring program this year was 508,896, an increase of 22,002 people compared with that of the previous year with the gender ratio of 1.03:1 between male and female.

In 2005, the total number of health institutions at all levels within the monitoring areas was 303, down by 7 compared with that of the previous year. The total number of hospital beds in these institutions was 4,071, up by 446 beds compared with that of the previous year. The total number of public health workers in these institutions was 3,703, down by 344 people against that of 2004, this was mainly due to the population migration of the Three Gorges Reservoir area.

7.2 Life Statistics

7.2.1 Birth and death

There were altogether 3,907 babies born within the monitoring areas in 2005 with the birth rate of 7.68‰, down by 6.68% compared with that of the previous year. Among all the new babies 2,064 were male and 1,843 female. The total number of death was 3,016, among them, 1,741 were male and 1,275 female. The mortality rate was 5.93‰, up by 4.40% compared with that of the previous year. The death rate was 6.74‰ for male and 5.09‰ for female. The death rate of Chongqing Municipality, Fengdu, Wanzhou and Yichang monitoring stations was 4.23‰, 7.25‰, 5.85‰ and 7.11‰ respectively. Compared with that of the previous year, the death rate had a slight reduction in Chongqing but some rise in Yichang, Wanzhou and Fengdu. There were 50 cases of baby death, 28 male and 22 female. The infant mortality was 12.80‰, slightly higher than the level of the previous year but significantly lower than the national average (21.50‰ in 2004).

7.2.2 Analysis of death cause

In 2005, the comparison among cause of death, gender and mortality of the top 5 causes of death for different gender indicated that circulatory diseases was the No. 1 killer for both men and women. The order of the top 5 causes of death were: circulatory diseases, malignant tumor, respiratory diseases, injury and poisoning and acatalepsia diseases. The death toll resulting from these 5 diseases accounted for 88.00% of the total, indicating that they were major killers for dwellers in the Three Gorges Reservoir areas. Compared with 2004, the No.5 killer was acatalepsia diseases replacing digestive diseases. The death percentages of circulatory diseases and malignant tumor had some rise, while that of respiratory diseases and injury and poisoning dropped to some extents.

7.3 Disease Monitoring

7.3.1 Infectious Diseases Monitoring

In 2005, a total number of 3,811 cases of infectious diseases were reported from all the monitoring sites with the total morbidity of 748.88 per 100,000 people. Two death cases were reported with total death rate of 0.39 per 100,000 people. There was no report on the case of Class A infectious diseases. However, 3,037 cases of 12 types of Class B infectious diseases were reported with morbidity of 596.78 in every 100,000 people. A total of 774 cases of 5 types of Class C infectious disease were reported with the morbidity of 152.09 per 100,000 people. Compared with that of the previous year, the incidence of Class B infectious diseases went up by 17.12% and the incidence of Class C infectious diseases went down by 23.97%. For Class B infectious diseases Fengdu had the highest incidence (1036.16/100,000 people) but Yichang had the lowest incidence (238.81/100,000 people). The incidence of Class C infectious diseases was the highest in Wanzhou (263.81/100,000 people) and lowest in Yichang (67.23/100,000 people). The top 5 types of Class B infectious diseases were viral hepatitis (301.83 in every 100,000), TB (197.09 in every 100,000), dysentery (47.75 in every 100,000), gonorrhea (33.60 in every 100,000) and syphilis (10.61 in every 100,000). Dysentery took the place of gonorrhea compared with that of last year.

For the structure of the infectious diseases under national monitoring program, blood and sexually transmitted diseases, respiratory diseases, digestive diseases and natural epidemic focus-based diseases took up 43.27%, 32.01%, 24.30% and 0.13% of the total respectively. Compared with that of the previous year, blood and sexually transmitted diseases rose to the top position while respiratory diseases went down to the second place. Whooping cough moved out of the list but haemorrhagic fever was added into the type list of infectious diseases. The incidences of hepatitis A and typhoid fever relevant to the impoundment due to water as their transmission medium and that of natural epidemic focus-based diseases haemorrhagic fever and encephalitis B relevant to biological media were at relatively low level.

7.3.2 Endemic Diseases Monitoring

In 2005, the monitoring stations at Chongqing, Wanzhou and Fengdu took random investigations on iodine deficiency of 773 children aged 8-12. Among them, 94 had Io thyroid enlargement with the enlargement rate of 12.16%, up by 3.45 percentage points compared with that of the previous year but falling into the slight prevalence. Thyroid enlargement rate was 14.05% in Wanzhou, 12.50% in Fengdu and 7.77% in Chongqing, up by 7.17 percentage points in Wanzhou and 0.62 percentage points in Fengdu and down by 2.12 percentage points in Chongqing compared with that of 2004. The findings of salt consumption of 1,417 households showed that 1,351 households consumed iodized salt with the coverage of 95.34%, down by 2.08 percentage points compared with that of 2004. Among the 1,351 household, 1,290 consumed the iodine-added salt that was qualified with the salt qualification rate of 95.48% and the consumption rate of such salt being 91.04%, up by 2.81 and 1.05 percentage points compared with that of the previous year.

The investigation on endemic fluorine diseases in Fengjie County of Chongqing and Zigui County of Yichang showed that 36 of the 195 people under the investigation suffered from endemic fluorine disease, accounting for 18.46%.

The IHA testing result on serum antibody for schistosomiasis at Wanzhou monitoring site showed 3 positive cases among the 503 tested people, accounting for 0.60%. Among the 89 local ship workers and other workers having frequent visit to the schistosomiasis prevalent region, 3 cases showed positive, taking up 3.37%. There were also 3 positive cases among the 105 people from the prevalent region who did business in Wanzhou, accounting for 2.86%. In addition, no egg of schistosome was detected from the stool samples of 450 local residents.

The test results on serum antibody of leptospirosis of healthy population of each monitoring   site showed 55 positive cases among 1,324 samples with positive case rate of 4.15%. The monitoring site of Chongqing had the highest rate of 8.80%, while no positive case occurred at the monitoring site of Yichang.

7.4 Biological Media Monitoring

7.4.1 Mouse Monitoring

The indoor mouse density was 4.08% in 2005, up by 2.41 percentage points compared with that of 2004 but similar to the average level of the 5 years before second-stage impoundment (3.94%). The mouse density in spring was lower than that in autumn. The outdoor mouse density was 3.90%, lower than the average level of the 5 years before second-stage impoundment (4.22%) but 1.21 percentage points higher than that of the previous year. The outdoor mouse density was higher in spring than in autumn. In spring, outdoor mouse density (4.50%) was higher than the indoor density（2.58%）and vice versa in autumn. This is mainly because that there are no small insect eating animals (e.g. muskrat and small mouse) in houses in spring but many in outdoor environment.

Sewer rat dominated the indoor mouse species, accounting for 82.35% of the total. Buff-breasted mouse ranked the second and took up 11.76%. In outdoor environment, small beast of insectivore (mainly short-tailed shrew) still dominated all other species and accounted for 85.71% of the total. Sewer rat (9.52%) was the second and the amount of both black strip rat and buff-breasted mouse was relatively small, less than 3%. Black strip rat (Apodemus agrarius) was the host animal for epidemic haemorrhagic fever virus and leptospirosis, its percentage dropped from 7.96% of 2004 to 2.38% in 2005, continuously maintaining a low level. Among all monitoring sites, Fengdu had the highest indoor mouse density at 4.08% while Yichang had the lowest of 1.20%. As for outdoor mouse density, Fengdu was the highest at 3.90% while Wanzhou was the lowest at 0.33%.

In 2005, all monitoring sites carried out relevant tests on the lung (286) and kidney (325) samples of mice or rats to identify the infection causes of epidemic haemorrhagic fever virus and leptospirosis. The findings showed 2 positive cases on leptospirosis. The positive rate of epidemic haemorrhagic fever virus was 0.68% in Chongqing, 4.00% in Fengdu and 8.89% in Wanzhou. However, there were few such patients. And no positive case occurred in Yichang.

7.4.2 Mosquitoes Monitoring

In the year 2005, the overall adult mosquito density in livestock pen of all monitoring sites was 113.74/(pen·artificial hour), lower than 132.76/(pen·artificial hour) of 2004 or the average level of the 5 years before second-stage impoundment [198.57/(pen·artificial hour)]. The overall indoor adult mosquito density was 32.76/(pen·artificial hour), lower than the level of 36.82/(pen·artificial hour) of the previous year or the average level of the 5 years before second-stage impoundment [63.97/(pen·artificial hour)]. Compared with that of the previous year, the adult mosquito density of livestock pen of all monitoring sites enjoyed some reduction with most significant decrease in Fengdu monitoring site. Except in Wanzhou, the indoor adult mosquito density of the other monitoring sites also enjoyed reduction at different degree.

The change of both indoor adult mosquito density and livestock-pen adult mosquito density showed the same 10-day trend between May and September. 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 [46.15/(pen·artificial hour)] and lowest in Yichang [10.04/(pen·artificial hour)]. At the same time, the mosquito density in livestock pens was the highest in Wanzhou [163.56/(pen·artificial hour)] and the lowest in Fengdu [78.84/(pen·artificial hour)].

Regarding the composition of mosquito species, Desvoidea obturbans dominated both residential buildings and livestock pens, accounting for 59.71% and 59.29% of the total number respectively. Similar to the previous year, the No.2 species of mosquito was culex pipiens fatigans, it accounted for 20.41% in residential buildings. No.3 was Anopheles sinensis，taking up 14.06%.