[Epidemic situation and diagnosis of imported malaria before and after malaria elimination in Nanjing City, Jiangsu Province]

OBJECTIVE

To analyze the epidemiological characteristics and diagnosis of imported malaria before and after malaria elimination in Nanjing City of Jiangsu Province, so as to provide the scientific evidence for formulating the malaria control strategy after malaria elimination.

METHODS

Data pertaining to the epidemic situation and individual investigation of malaria in Nanjing City before (from 2012 to 2016) and after malaria elimination (from 2017 to 2020) were captured from the National Notifiable Communicable Disease Reporting System and the Information System for Parasitic Diseases Control and Prevention and were analyzed statistically.

RESULTS

A total of 178 malaria cases were reported in Nanjing City from 2012 to 2020, and all were imported cases. There were 99 malaria cases reported before malaria elimination in Nanjing City, including 78 cases with Plasmodium falciparum malaria (78.79%), 5 cases with P. vivax malaria (5.05%), 10 cases with P. ovale malaria (10.10%), 3 cases with P. malariae malaria (3.03%) and 3 cases with mixed infections (3.03%), and 79 malaria cases reported after elimination, including 63 cases with P. falciparum malaria (79.75%), 5 cases with P. vivax malaria (6.33%), 9 cases with P. ovale malaria (11.39%), 2 cases with P. malariae malaria (2.53%). There was no significant difference in the proportion of each type of malaria cases in Nanjing City before and after malaria elimination (χ² =2.400, P > 0.05). Malaria cases mainly acquired Plasmodium infections in African regions, and no significant difference was seen in the proportion of malaria cases returning to Nanjing City from African countries before and after malaria elimination (χ² = 0.093, P > 0.05). The number of malaria cases peaked in Nanjing City in January and during the period from May to July before elimination, and there was no apparent seasonal variation in the distribution of malaria cases after elimination. The proportion of malaria cases living in Nanjing City was significantly greater after malaria elimination than before elimination (72.15% vs. 55.56%; χ² = 5.187, P = 0.023). The proportions of businessmen and international students were both 5.05% before malaria elimination, and increased to 15.19% and 13.92% after elimination, respectively (χ² = 5.229 and 4.229, both P values < 0.05). The percentage of definitive diagnosis of malaria at initial diagnosis was 18.75% in county-level hospitals before malaria elimination and increased to 61.11% after elimination (χ² = 6.275, P = 0.012), while the proportion of malaria cases with definitive diagnoses in county-level hospitals was 4.04% before malaria elimination and increased to 13.92% after elimination (χ² = 5.562, P = 0.018). During the period from 2012 to 2020, the proportion of malaria cases with definitive diagnoses within 1 to 3 days post-admission increased from 27.27% in Nanjing City before malaria elimination to 45.57% after elimination (χ² = 6.433, P = 0.011).

CONCLUSIONS

The epidemic situation of imported malaria remains serious in Nanjing City during the post-elimination stage, and malaria parasite infections predominantly occur in African regions. In addition, there are changes in regional and occupational distributions of malaria cases and the diagnostic capability of malaria increases in county-level hospitals in Nanjing City after malaria elimination. Further improvements in the malaria surveillance system and the diagnostic and treatment capability of malaria in medical institutions at each level are required to consolidate malaria elimination achievements in Nanjing City.

[Distribution Characteristics and Source Analysis of Water-soluble Ions in Particulate Matter Under Different Weather Processes in Nanjing]

From November 16 to 28 2018, water-soluble ions in particulate matter and some trace gases in Nanjing City were observed using the online gas composition and aerosol monitoring system MARGA ADI 2080. Combined with meteorological elements and sounding data, the distribution characteristics and day-night differences of pollutants and water-soluble ions during haze, fog, clear, and precipitation processes were analyzed. The results show that the average concentration of PM_2.5 varied from 26.9μg·m^-3 (precipitation) to 96.4μg·m^-3 (haze) while total water-soluble ions varied between 23.7μg·m^-3 (precipitation) and 89.7μg·m^-3 (haze). The ranked order of ion concentrations was NO₃^- > NH₄⁺ > SO₄^2- > Cl^- > K⁺ > Ca²⁺ > Na⁺ > Mg²⁺ during haze and fog events, and NO₃^- > SO₄^2- > NH₄⁺ > Cl^- > Ca²⁺ > K⁺ > Na⁺ > Mg²⁺ during clear weather and precipitation period. The diurnal distributions of water-soluble ions were quite different under the four conditions, although SO₄^2-, NO₃^-, and NH₄⁺(SNA) were ranked haze > fog > clear > precipitation for both day and night periods. According to the PMF source analysis, secondary sources were the main factors affecting haze; secondary sources, sea salt, and combustion sources were the main pollution sources to foggy conditions; and the removal effect of precipitation on coal-fired sources and secondary sources was more notable than during clear conditions.

[Effect of integrated schistosomiasis control measures on Oncomelania snails in river channels connecting the Yangtze River in Nanjing City]

OBJECTIVE

To evaluate the effectiveness of Oncomelania snails control following the implementation of integrated schistosomiasis control measures in river channels connecting the Yangtze River in endemic areas of Nanjing City.

METHODS

The river channels connecting the Yangtze River with snails in Nanjing City were selected as the study pilots. The integrated schistosomiasis control measures implemented in the study pilots were investigated by means of retrospective analyses and field surveys from 1998 to 2019, and the effectiveness of snail control was evaluated.

RESULTS

Integrated control measures with emphases on environmental improvements including water resource projects for schistosomiasis control were implemented in the study pilots during the period from 1998 to 2019, including river bank concretion with 84.51 km in length, marshland cutting and dredging with 50.41 km in length, building 2 sluices and 3 overflow dams, digging one floodway and snail control with chemical treatment that covered an area of 3 370.80 hm². No Schistosoma japonicum infection had been detected in snails since the completion of the integrated control measures. In addition, snails had been eliminated in 6 river channels connecting the Yangtze River until 2019, with the snail habitats reducing from 214.33 hm² to 52.22 hm² in 10 river channels connecting the Yangtze River and the snail density reducing to below 0.1 snails/0.1 m² in snail-breeding river channels connecting the Yangtze River.

CONCLUSIONS

The integrated schistosomiasis control measures with emphases on environmental improvements may effectively control snail breeding and spread in rivers connecting the Yangtze River in endemic areas of schistosomiasis; however, the maintenance of the project and snail surveillance and control should be intensified following the completion of the integrated schistosomiasis control measures.

[Investigation of Toxoplasma gondii infection among special populations in Nanjing City, Jiangsu Province]

OBJECTIVE

To understand the prevalence of Toxoplasma gondii infection among special populations in Nanjing City, so as to provide the reference for formulating the interventions for the prevention and control of T. gondii infections in this population.

METHODS

The HIV/AIDS patients, tumor patients, pregnant women, and people with livestock and poultry breeding or processing works were selected as the study subjects from September to November 2015. The venous blood samples were collected from each participant for detecting IgG and IgM antibodies against T. gondii by ELISA.

RESULTS

The overall prevalence of T. gondii infection was 10.2% in the study subjects in Nanjing City. The T. gondii infection rates were 12.2%, 11.3%, 4.0%, and 13.0% among the HIV/AIDS patients, tumor patients, pregnant women, and people with livestock and poultry breeding or processing works, respectively, and there was no statistically significant difference among the four groups (χ² = 5.668, P = 0.130). The prevalence of T. gondii infection was higher in men than in women (15.3% vs. 5.8%; χ² = 10.213, P = 0.001), and there were significant differences in the prevalence of T. gondii infection in terms of gender (χ² = 9.501, P = 0.023), education levels (χ² = 9.850, P = 0.043) or occupations (χ² = 8.983, P = 0.062).

CONCLUSIONS

The infection rate of T. gondii among the special population in Nanjing City is high. Therefore, the health education intervention should be strengthened in the follow-up work for the special population.

[Pollution Levels and Risk Assessment of Heavy Metals from Atmospheric Deposition in Nanjing]

In order to evaluate the pollution levels of and risk from heavy metals in the atmospheric deposition of different functional urban districts, dust samples were collected from 20 sampling sites in typical industrial, traffic, residential, and educational districts of Nanjing. The concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti, V, and Zn were analyzed. The potential ecological risk and health risk were evaluated using the potential ecological risk index and U.S. EPA's health risk assessment models. Enrichment factors, correlation analysis, and principal component analysis were used to analyze the sources of heavy metals. Results showed that the concentrations of As, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn were the highest in the industrial district and the concentrations of Ba, Ni, Ti, and V were the highest in the traffic district. The value of the potential ecological risk index was the highest in the industrial district and lowest in the educational district. Meanwhile, the ecological risk of Cr was the highest, achieving a moderate ecological hazard level. None of the studied heavy metals had noncarcinogenic risk or carcinogenic risk, according to the results of health risk assessment. Source analysis indicated that heavy metals in the atmospheric deposition from the study areas were mainly from traffic and industrial activities, coal combustion, natural process and life sources.

[Assessment of the potential for urban facade greening in Xinjiekou District, Nanjing, China.]

Green facade is an important strategy to improve the urban eco-environment and reduce the negative effects of human activities in central districts of cities which are land-scarce and lack green spaces. We first summarized the limiting factors for the construction of green facades locally and internationally. Then, we used the Xinjiekou District of Nanjing City in China as a case study area, and selected the wind environment, solar environment, and physical build environment that might impact the potential development of green facades as key factors to quantitatively analyze singlely by geographic information systems (GIS) and computational fluid dynamics (CFD). Finally, the potential area to develop green facades was assessed through a multi-factor overlay analysis. The results showed that 17726 m² of wall spaces in the Xinjiekou District had a high potential for facade greening, accounting for 30.8% of all exterior wall space under a height of 12 m and 17.3% of the entire study area. Sunlight was a key limiting factor in determining whether a green facade should be developed. Irrigation was identified as another important factor that might strongly affect the growth of vertical vegetation in urban environment. The spatial distribution of walls suitable for facade greening was uneven, with an "inner-high and south-high" spatial pattern. Our results would help to guide the design and development of green facades in Xinjiekou, and also provide a reference for planning and utilizing green wall space projects in other built and dense urban areas.

[Cryptosporidium infection in Nanjing City from 2015 to 2016]

OBJECTIVE

To investigate the status of Cryptosporidium infection in the population in Nanjing City so as to provide the evidence for the prevention and control of cryptosporidiosis.

METHODS

A total of 100 fecal samples were collected from each of three districts (Liuhe, Qixia and Gaochun) and one hospital (Nanjing Zhongda Hospital) in 2015 and 2016 respectively. The fecal samples were detected for Cryptosporidium with microscopy (by using the gold amine phenol-modified acid-fast staining) and the positive samples were detected again for the molecular biology confirming by using the fluorescence quantitative PCR.

RESULTS

During the two years, 581 cases of normal population who lived in the city were surveyed and no Cryptosporidium infection was found. Among 202 cases of outpatients with chronic diarrhea, there were 9 Cryptosporidium positive cases with the microscope scanning method (4.46%), and among the 9 cases, 7 cases showed obvious logarithmic amplification curves showing positive Cryptosporidium nucleic acid, but 2 cases without the obvious logarithmic amplification curves, and the Cryptosporidium nucleic acid positive rate was 3.47%.

CONCLUSIONS

Cryptosporidium infection is not found in the normal population of Nanjing City, but the Cryptosporidium infection is found in the chronic diarrhea patients. The results imply that we should strengthen the detection of Cryptosporidium in the chronic diarrhea patients, so as to provide the evidence for improving the diagnosis and treatment of cryptosporidiosis.

[Analysis of human intestinal nematode infections in Nanjing City from 2006 to 2015]

OBJECTIVE

To analyze the epidemiological situation of human intestinal nematode infections in Nanjing City from 2006 to 2015, so as to provide the reference for formulating prevention and control measures.

METHODS

The surveillance data of human intestinal nematode infections in Nanjing City from 2006 to 2015 were collected and analyzed statistically.

RESULTS

From 2006 to 2015, 98 804 person-times of residents were surveyed in Nanjing City, and 465 person-times of residents were detected with intestinal nematode infections. The highest infection rate was in 2006 (1.97%), and the lowest in 2013 and 2015 (both 0.05%). Moreover, the positive rate of human intestinal nematode infections showed a significantly declining trend in total ( χ² = 552.19, P < 0.001). Meanwhile, the numbers of Ascaris lumbricoides, hookworm and Trichuris trichura cases were 329, 98 and 25 respectively, and the infection rates were 0.33%, 0.10% and 0.03% respectively. Among them, 443 cases had mild infection intensity (98.66%). There were 462 cases of single-infection (99.35%), and 3 of co-infection of two parasites (0.65%). From 2006 to 2015, 92 539 person-times of children under 12 years old were surveyed for Enterobius vermicularis infection and 352 cases were detected with E. vermicularis infection. Moreover, the positive rate showed a significantly decreasing trend in total (χ² = 147.94, P <0.001).

CONCLUSIONS

The control effect of human intestinal nematode infections in Nanjing City is remarkable. However, the surveillance and health education in key groups still should be strengthened, and the prevention and control programs should be adjusted promptly to further consolidating the effectiveness of intestinal nematode disease prevention and control.

[Interactive Effects of the Influencing Factors on the Changes of PM2.5 Concentration Based on GAM Model]

In this paper,the generalized additive model (GAM) was introduced to analyze the interactive effects of the influencing factors on the change of PM_2.5 concentration during 2013-2015 in Nanjing city.The results showed as follows:PM_2.5 and its influencing factors appeared to follow normal distribution.There were strong correlations among the influencing factors,especially among the temperature (TEM),pressure (PRS) and water vapor pressure (VAP).For the single influencing factor GAM models of PM_2.5 concentration,all influencing factors passed the significance test.Moreover,the equation fitting degrees of SO₂,CO,and NO₂ were much higher.In the multiple influencing factors GAM models of PM_2.5 concentration,the contribution of the SO₂,CO,NO₂,O₃,precipitation (PRE),wind and relative humidity (RHU) to the change of PM_2.5 concentration was 73.9% with significant impacts on the change of PM_2.5 concentration.Based on the diagnostic analysis of the effect of multi factors on the change of PM_2.5 concentration,there were linear relationship between PM_2.5 and SO₂,NO₂ and wind,and non-linear relationship between PM_2.5 and CO,O₃,PRE and RHU.The GAM models,which considered the interaction of SO₂ respectively with CO,PRE and RHU,the interaction of CO respectively with NO₂,O₃,PRE,Wind and RHU,and the interaction of NO₂ respectively with Wind、PRE and RHU,all passed the significance test (P<0.01 or P<0.05).The interaction of SO₂,CO and NO₂ respectively with other factors such as meteorological factors had the most important influence on the change of PM_2.5 concentration.At last,through the visualized three-dimensional map of the GAM models considering the interaction of the influencing factors on the PM_2.5 concentration,the interactive effects of the influencing factors on PM_2.5 concentration were quantitatively modeled.Our results demonstrated that GAM could be used to quantitatively analyze the interactive effect of the influencing factors on the change of PM_2.5 concentration.Therefore,the research method is innovative and important for PM_2.5 pollution and control.

[Endemic situation of schistosomiasis at national surveillance sites in Nanjing City, 2015]

OBJECTIVE

To understand the dynamic endemic situation of schistosomiasis in Nanjing City, 2015, so as to provide evidences for policy-making of schistosomiasis control.

METHODS

According to The National Scheme of Schistosomiasis Surveillance (2014), the endemic situation of schistosomiasis was monitored in 11 national surveillance sites in Nanjing.

RESULTS

The positive rates of serological (IHA) and stool examinations were 2.97% (97/3 269) and 0 for local residents, and 0.52％ (12/2 298) and 0 for migrant people, respectively. No schistosome-infected livestock was found. Totally 147.295 3 hm² area with Oncomelania hupensis snails were found, but no schistosome-infected snails were discovered.

CONCLUSIONS

The endemic situation of schistosomiasis declines greatly in Nanjing City in 2015. However, the control work still should be strengthened to consolidate the achievements of schistosomiasis control.

[Epidemiological analysis of malaria prevalence in Nanjing City from 2010 to 2015]

OBJECTIVE

To analyze the epidemiological characteristics of malaria in Nanjing City, so as to provide the evidence for further formulating and adjusting the malaria prevention and control strategy.

METHODS

The data of malaria situation, malaria cases and epidemiological investigations were collected from the Internet Reporting System in Nanjing City from 2010 to 2015 and analyzed statistically.

RESULTS

A total of 137 confirmed malaria cases were reported in Nanjing City from 2010 to 2015, including 102 falciparum malaria cases (74.45%), 33 vivax malaria cases (24.09%), one ovale malaria case (0.73%) and one quartan malaria case (0.73%). Among the 137 malaria cases, 126 cases (91.97%) were imported from foreign countries, 2 cases (1.46%) were infected locally, and nine cases (6.57%) were imported from other provinces in China. Among the 126 overseas imported cases, 117 cases were imported from African countries and 9 from Asian countries. These malaria cases were majorly young men working as migrant workers, laborers and technical persons. About 19.30% of the cases went to hospital on onset day, and 55.65% were confirmed by medical institutions as malaria in the same day. The majority of diagnosis institutions were municipal hospitals (74.45%).

CONCLUSIONS

The number of malaria cases in Nanjing City is declining year by year. The local infections are eliminating gradually. However, the situation of imported malaria from overseas is still serious. Therefore, the surveillance work and health education still should be strengthened, so as to reduce the risk of imported malaria.

[Scale effect of Nanjing urban green infrastructure network pattern and connectivity analysis.]

Based on ArcGIS, Erdas, GuidosToolbox, Conefor and other software platforms, using morphological spatial pattern analysis (MSPA) and landscape connectivity analysis methods, this paper quantitatively analysed the scale effect, edge effect and distance effect of the Nanjing urban green infrastructure network pattern in 2013 by setting different pixel sizes (P) and edge widths in MSPA analysis, and setting different dispersal distance thresholds in landscape connectivity analysis. The results showed that the type of landscape acquired based on the MSPA had a clear scale effect and edge effect, and scale effects only slightly affected landscape types, whereas edge effects were more obvious. Different dispersal distances had a great impact on the landscape connectivity, 2 km or 2.5 km dispersal distance was a critical threshold for Nanjing. When selecting the pixel size 30 m of the input data and the edge wide 30 m used in the morphological model, we could get more detailed landscape information of Nanjing UGI network. Based on MSPA and landscape connectivity, analysis of the scale effect, edge effect, and distance effect on the landscape types of the urban green infrastructure (UGI) network was helpful for selecting the appropriate size, edge width, and dispersal distance when developing these networks, and for better understanding the spatial pattern of UGI networks and the effects of scale and distance on the ecology of a UGI network. This would facilitate a more scientifically valid set of design parameters for UGI network spatiotemporal pattern analysis. The results of this study provided an important reference for Nanjing UGI networks and a basis for the analysis of the spatial and temporal patterns of medium-scale UGI landscape networks in other regions.