Communicable Disease Control ; methods ; trends

Objective: To optimize the warning threshold values of common communicable diseases in Gansu province, and improve the early warning effect. Method: An early warning model was set up for influenza, scarlet fever, other infectious diarrheal diseases, dysentery, typhoid and paratyphoid, viral hepatitis type E and hand foot and mouth disease (HFMD) respectively in Gansu by using the moving percentile method and cumulative sum method. By calculating the sensitivity, specificity, predictive value of positive test, predictive value of negative test, Youden' index and receiver-operating characteristic curve, the optimum early warning threshold values for communicable diseases in Gansu were selected. Results: The optimum early warning boundary values of influenza, scarlet fever, other infectious diarrheal diseases, dysentery, typhoid and paratyphoid, and viral hepatitis type E were P(90), P(80), P(95), P(90), P(80) and P(90) respectively. The optimum early warning parameters of HFMD were k=1.2, H=5σ. Under the optimum early warning boundary values/parameters, the early warning sensitivities of influenza, scarlet fever, other infectious diarrheal diseases, dysentery, typhoid and paratyphoid, viral hepatitis type E and HFMD were 86.67%, 100.00%, 91.67%, 100.00%, 100.00%, 100.00% and 100.00%, the specificities were 86.49%, 62.22%, 75.00%, 100.00%, 97.92%, 89.13% and 74.47%. The predictive values of positive test were 72.22%, 29.17%, 52.38%, 100.00%, 80.00%, 54.55% and 29.41%, and the predictive values of negative test were 94.12%, 100.00%, 96.77%, 100.00%, 100.00%, 100.00% and 100.00%, and the Youden' indexes were 0.73, 0.62, 0.67, 1.00, 0.98,0.89 and 0.74. Receiver-operating characteristic curve showed that the values/parameters of this warning boundary were the points closest to the upper left of the coordinate diagram. Conclusion: The early warning thresholds of influenza, other infectious diarrheal diseases, dysentery and hepatitis E in Gansu may be raised appropriately and the early warning parameters of HFMD need to be adjusted to improve the effectiveness of early warning.
China ; Communicable Disease Control/methods* ; Communicable Diseases/epidemiology* ; Disease Notification ; Disease Outbreaks/prevention & control* ; Humans ; Models, Theoretical ; Population Surveillance/methods*

Communicable Disease Control ; Communicable Diseases ; Disease Notification ; Humans ; Population Surveillance ; methods

OBJECTIVETo investigate the application of prospective space-time scan statistic in the early stage of detecting infectious disease outbreaks.

METHODSThe prospective space-time scan statistic was tested by mimicking daily prospective analyses of bacillary dysentery data of Chengdu city in 2005 (3212 cases in 102 towns and villages). And the results were compared with that of purely temporal scan statistic.

RESULTSThe prospective space-time scan statistic could give specific messages both in spatial and temporal. The results of June indicated that the prospective space-time scan statistic could timely detect the outbreaks that started from the local site, and the early warning message was powerful (P = 0.007). When the merely temporal scan statistic for detecting the outbreak was sent two days later, and the signal was less powerful (P = 0.039).

CONCLUSIONThe prospective space-time scan statistic could make full use of the spatial and temporal information in infectious disease data and could timely and effectively detect the outbreaks that start from the local sites. The prospective space-time scan statistic could be an important tool for local and national CDC to set up early detection surveillance systems.

China ; Communicable Disease Control ; methods ; Communicable Diseases ; epidemiology ; Humans ; Models, Statistical ; Population Surveillance ; methods ; Prospective Studies

OBJECTIVETo analyze and evaluate the application of China Infectious Diseases Automated-alert and Response System(CIDARS)in Zhejiang province.

METHODSData through the monitoring program in 2012 was analyzed descriptively and compared with the incidence data in the same period as well information related to public health emergency events.

RESULTSA total of 14 292 signals were generated on 28 kinds of infectious diseases in the system, in Zhejiang province. 100% of the signals had been responded and the median time to response was 0.81 hours. 123 signals (0.86%)were preliminarily verified as suspected outbreaks and 33 outbreaks were finally confirmed by further field investigation, with a positive ratio of 0.23% . Information related to regional distribution showed significant differences which reflecting a positive correlation between the numbers of diseases and the time of early-warning(r = 0. 97, P < 0.01). Distribution of information related to different types of diseases was also significantly different, showing a positive correlation between the prevalent strength of the disease and the amount of information in a specific area(r = 0.80, P < 0.01).

CONCLUSIONCIDARS had a good performance which could be used to assist the local public health institutions on early detection of possible outbreaks at the early stage. However, the effectiveness was different for different regions and diseases.

China ; epidemiology ; Communicable Disease Control ; methods ; Communicable Diseases ; epidemiology ; Disease Outbreaks ; prevention & control ; Humans ; Incidence ; Population Surveillance ; methods ; Public Health

OBJECTIVEforecast the epidemic trend and to evaluate the effect of outbreak control measures by investigation of a varicella outbreak event with a discrete time delay SEIR model.

METHODSA discrete time delay model was formulated by discretization method based on a continuous SEIR model with the consideration of the time delay effect on latent period and communicable period. The epidemic trend forecast was carried out based on the number of expected cases. The theoretical effect evaluation was assessed by comparing the results from different emergency control measures.

RESULTSWithout any control measures, the theoretical attack rate was 30.16% (504/1671). The course of the epidemic lasted for 4 months and the peak epidemic time was 78 days after the onset of the first case. 'Generation' phenomenon had been observed in the course of the epidemic with the interval of two weeks. The actual number of cases was decreased by 89.48% (451/504) compared with the number of expected cases under no control measure scenario. With the rigorous quarantine measure for all cases on their onset day, when the measure was conducted on 0, 14, 28, 42 days after the onset of the first case, the total numbers of expected cases were 22, 59, 127 and 220 respectively. With the quarantine measure conducted on 14 days after the onset of the first case, when the proportion of quarantine was 30%, 50%, 70%, 90%, the total number of expected cases were 485, 457, 386 and 169, respectively. With the emergent vaccination for all persons, when the measure was conducted on 0, 14, 28, 42 days after the onset of the first case, the total numbers of expected cases were 7, 26, 81 and 202 respectively. With the emergent vaccination conducted on 14 days after the onset of the first case, when the immunization coverage rate was 30%, 50%, 70%, 90%, the total numbers of expected cases were 354, 246, 127 and 40, respectively.

CONCLUSIONThe number of expected cases can be regarded as the reference to evaluate the effect of control measures. The simulation results suggest that it will get more benefits to conduct control measures earlier in varicella outbreak events, and the effect of emergent vaccination is better than that of quarantine measure under the same conditions.

Chickenpox ; epidemiology ; prevention & control ; Communicable Disease Control ; methods ; Disease Outbreaks ; prevention & control ; Humans ; Incidence ; Models, Theoretical

OBJECTIVETo analyze the current situation on China Infectious Disease Automated-alert and Response System (CIDARS) in Guangdong province, China.

METHODSEarly-warning signals and response time were analyzed by using three approaches of CIDARS. Positive rates of early-warning signals and error early-warning rates prior and after the adjustment,were compared.

RESULTSTotally, 114 585 early-warning signals appeared, with an average response time of 1.35 hours from April 21, 2008 to December 31, 2012. There were 12,394 early-warning signals in terms of fixed threshold method with a positive rate of 7.96%. 85 727 early-warning signals appeared under the mobile percentile method with a positive rate of 0.85%. There were 16,464 early-warning signals by using accumulation and control chart methods,with a positive rate of 1.82%. Results showed there was a positive correlation between the number of reported cases and the number of early-warning signals (r = 0.924, P < 0.01). The overall positive rate in Guangdong province increased from 1.48% to 2.14%, after the adjustment done by the Chinese Center for Disease Control and Prevention in 2010. The error early-warning rates regarding eight infectious diseases including hepatitis A, bacillary or amebic dysentery, both typhoid and paratyphoid fevers had reduced.

CONCLUSIONThe early-warning signal response appeared timely in CIDARS with good operation. However, despite the improvement on the efficacy of CIDARS, some functions and parameters of the systems still need to be adjusted.

China ; Communicable Disease Control ; methods ; Disease Outbreaks ; prevention & control ; Humans ; Population Surveillance ; methods

China ; epidemiology ; Communicable Disease Control ; methods ; Communicable Diseases ; epidemiology ; Disasters ; Humans

OBJECTIVETo analyze and further improvement the application of the China Infectious Diseases Automated-alert and Response System (CIDARS) in Guangxi Zhuang Autonomous Region.

METHODSResults related to the amount of signal, proportion of signal responded, time to signal response, manner of signal verification and on each signal of Guangxi in CIDARS from 2009 to 2011 were described. Performance was compared between the periods of pre/ post the adjustment of parameters in CIDARS on December 10, 2010.

RESULTSA total of 29 788 signals were generated on 16 infectious diseases in the system in Guangxi. 100% signals had been responded with the median time to response as 1.5 hours. The average amount of signal per county per week was 1.7;with 624 signals(2.09%)verified as suspected outbreaks preliminarily and 191 outbreaks of 9 diseases were finally confirmed by further field investigation. The sensitivity of CIDARS was 89.25% , and the timeliness of detection was 2.8 d. After adjusting the parameter of CIDARS, the number of signals reduced, and the sensitivity and timeliness of detection improved for most of the diseases.

CONCLUSIONThe signals of CIDARS were responded timely, and the performance of CIDARS might be improved by adjusting the parameters of early-warning model, which helped enhance the ability of outbreaks-detection for local public health departments. However the current proportion of false positive signals still seemed to be high, suggesting that both the methods and parameters should be improved, according to the characteristics of different diseases.

China ; epidemiology ; Communicable Disease Control ; methods ; Communicable Diseases ; epidemiology ; Disease Notification ; methods ; Disease Outbreaks ; prevention & control ; Humans ; Models, Theoretical ; Population Surveillance ; methods

China ; epidemiology ; Communicable Disease Control ; methods ; organization & administration ; Communicable Diseases ; epidemiology ; Disease Outbreaks ; prevention & control ; Environmental Monitoring ; methods ; Epidemiologic Methods ; Epidemiological Monitoring ; Humans ; Risk Assessment ; methods ; Risk Factors