Study of the influence of meteorological factors on HFMD and prediction based on the LSTM algorithm in Fuzhou, China.

BACKGROUND: This study adopted complete meteorological indicators, including eight items, to explore their impact on hand, foot, and mouth disease (HFMD) in Fuzhou, and predict the incidence of HFMD through the long short-term memory (LSTM) neural network algorithm of artificial intelligence. METHOD: A distributed lag nonlinear model (DLNM) was used to analyse the influence of meteorological factors on HFMD in Fuzhou from 2010 to 2021. Then, the numbers of HFMD cases in 2019, 2020 and 2021 were predicted using the LSTM model through multifactor single-step and multistep rolling methods. The root mean square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE) and symmetric mean absolute percentage error (SMAPE) were used to evaluate the accuracy of the model predictions. RESULTS: Overall, the effect of daily precipitation on HFMD was not significant. Low (4 hPa) and high (≥ 21 hPa) daily air pressure difference (PRSD) and low (< 7 °C) and high (> 12 °C) daily air temperature difference (TEMD) were risk factors for HFMD. The RMSE, MAE, MAPE and SMAPE of using the weekly multifactor data to predict the cases of HFMD on the following day, from 2019 to 2021, were lower than those of using the daily multifactor data to predict the cases of HFMD on the following day. In particular, the RMSE, MAE, MAPE and SMAPE of using weekly multifactor data to predict the following week's daily average cases of HFMD were much lower, and similar results were also found in urban and rural areas, which indicating that this approach was more accurate. CONCLUSION: This study's LSTM models combined with meteorological factors (excluding PRE) can be used to accurately predict HFMD in Fuzhou, especially the method of predicting the daily average cases of HFMD in the following week using weekly multifactor data.

Study on the influence of meteorological factors on influenza in different regions and predictions based on an LSTM algorithm.

BACKGROUND: Influenza epidemics pose a threat to human health. It has been reported that meteorological factors (MFs) are associated with influenza. This study aimed to explore the similarities and differences between the influences of more comprehensive MFs on influenza in cities with different economic, geographical and climatic characteristics in Fujian Province. Then, the information was used to predict the daily number of cases of influenza in various cities based on MFs to provide bases for early warning systems and outbreak prevention. METHOD: Distributed lag nonlinear models (DLNMs) were used to analyse the influence of MFs on influenza in different regions of Fujian Province from 2010 to 2021. Long short-term memory (LSTM) was used to train and model daily cases of influenza in 2010-2018, 2010-2019, and 2010-2020 based on meteorological daily values. Daily cases of influenza in 2019, 2020 and 2021 were predicted. The root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE) and symmetric mean absolute percentage error (SMAPE) were used to quantify the accuracy of model predictions. RESULTS: The cumulative effect of low and high values of air pressure (PRS), air temperature (TEM), air temperature difference (TEMD) and sunshine duration (SSD) on the risk of influenza was obvious. Low (< 979 hPa), medium (983 to 987 hPa) and high (> 112 hPa) PRS were associated with a higher risk of influenza in women, children aged 0 to 12 years, and rural populations. Low (< 9 °C) and high (> 23 °C) TEM were risk factors for influenza in four cities. Wind speed (WIN) had a more significant effect on the risk of influenza in the ≥ 60-year-old group. Low (< 40%) and high (> 80%) relative humidity (RHU) in Fuzhou and Xiamen had a significant effect on influenza. When PRS was between 1005-1015 hPa, RHU > 60%, PRE was low, TEM was between 10-20 °C, and WIN was low, the interaction between different MFs and influenza was most obvious. The RMSE, MAE, MAPE, and SMAPE evaluation indices of the predictions in 2019, 2020 and 2021 were low, and the prediction accuracy was high. CONCLUSION: All eight MFs studied had an impact on influenza in four cities, but there were similarities and differences. The LSTM model, combined with these eight MFs, was highly accurate in predicting the daily cases of influenza. These MFs and prediction models could be incorporated into the influenza early warning and prediction system of each city and used as a reference to formulate prevention strategies for relevant departments.

Differences in the Epidemiology of Human Cases of Avian Influenza A(H7N9) and A(H5N1) Viruses Infection.

BACKGROUND: The pandemic potential of avian influenza viruses A(H5N1) and A(H7N9) remains an unresolved but critically important question. METHODS: We compared the characteristics of sporadic and clustered cases of human H5N1 and H7N9 infection, estimated the relative risk of infection in blood-related contacts, and the reproduction number (R). RESULTS: We assembled and analyzed data on 720 H5N1 cases and 460 H7N9 cases up to 2 November 2014. The severity and average age of sporadic/index cases of H7N9 was greater than secondary cases (71% requiring intensive care unit admission vs 33%, P = .007; median age 59 years vs 31, P < .001). We observed no significant differences in the age and severity between sporadic/index and secondary H5N1 cases. The upper limit of the 95% confidence interval (CI) for R was 0.12 for H5N1 and 0.27 for H7N9. A higher proportion of H5N1 infections occurred in clusters (20%) compared to H7N9 (8%). The relative risk of infection in blood-related contacts of cases compared to unrelated contacts was 8.96 for H5N1 (95% CI, 1.30, 61.86) and 0.80 for H7N9 (95% CI, .32, 1.97). CONCLUSIONS: The results are consistent with an ascertainment bias towards severe and older cases for sporadic H7N9 but not for H5N1. The lack of evidence for ascertainment bias in sporadic H5N1 cases, the more pronounced clustering of cases, and the higher risk of infection in blood-related contacts, support the hypothesis that susceptibility to H5N1 may be limited and familial. This analysis suggests the potential pandemic risk may be greater for H7N9 than H5N1.

Risk factors for influenza A(H7N9) disease--China, 2013.

BACKGROUND: The majority of human cases of novel avian influenza A(H7N9), which emerged in China in spring 2013, include reported exposure to poultry. However, specific host and exposure risk factors for disease are unknown, yet critical to design prevention measures. METHODS: In April-June 2013, we conducted a case-control study in 8 Chinese provinces. Patients with laboratory-confirmed A(H7N9) (n = 89) were matched by age, sex, and neighborhood to controls (n = 339). Subjects completed a questionnaire on medical history and potential exposures, including poultry markets and other poultry exposure. We used conditional logistic regression to calculate matched and adjusted odds ratios (ORs) for the association of A(H7N9) virus infection with potential risk factors. RESULTS: Fifty-five percent of patients compared with 31% of controls reported any contact with poultry (matched OR [mOR], 7.8; 95% confidence interval [CI], 3.3-18.8). Sixty-seven percent of patients compared with 35% of controls visited a live poultry market (mOR, 5.4; CI, 3.0-9.7). Visiting live poultry markets increased risk of infection even after adjusting for poultry contact and other confounders (adjusted OR, 3.4; CI, 1.8-6.7). Backyard poultry were not associated with increased risk; 14% of cases did not report any poultry exposure or market visit. Obesity (mOR, 4.7; CI, 1.8-12.4), chronic obstructive pulmonary disease (mOR, 2.7; CI, 1.1-6.9), and immunosuppressive medications (mOR, 9.0; CI, 1.7-47.2) were associated with A(H7N9) disease. CONCLUSION: Exposures to poultry in markets were associated with A(H7N9) virus infection, even without poultry contact. China should consider permanently closing live poultry markets or aggressively pursuing control measures to prevent spread of this emerging pathogen.

Transmission dynamics of symptom-dependent HIV/AIDS models.

In this study, we proposed two, symptom-dependent, HIV/AIDS models to investigate the dynamical properties of HIV/AIDS in the Fujian Province. The basic reproduction number was obtained, and the local and global stabilities of the disease-free and endemic equilibrium points were verified to the deterministic HIV/AIDS model. Moreover, the indicators $ R_0/ $ and $ R_0^e $ were derived for the stochastic HIV/AIDS model, and the conditions for stationary distribution and stochastic extinction were investigated. By using the surveillance data from the Fujian Provincial Center for Disease Control and Prevention, some numerical simulations and future predictions on the scale of HIV/AIDS infections in the Fujian Province were conducted.

Protection by face masks against influenza A(H1N1)pdm09 virus on trans-Pacific passenger aircraft, 2009.

In response to several influenza A(H1N1)pdm09 infections that developed in passengers after they traveled on the same 2 flights from New York, New York, USA, to Hong Kong, China, to Fuzhou, China, we assessed transmission of influenza A(H1N1)pdm09 virus on these flights. We defined a case of infection as onset of fever and respiratory symptoms and detection of virus by PCR in a passenger or crew member of either flight. Illness developed only in passengers who traveled on the New York to Hong Kong flight. We compared exposures of 9 case-passengers with those of 32 asymptomatic control-passengers. None of the 9 case-passengers, compared with 47% (15/32) of control-passengers, wore a face mask for the entire flight (odds ratio 0, 95% CI 0-0.71). The source case-passenger was not identified. Wearing a face mask was a protective factor against influenza infection. We recommend a more comprehensive intervention study to accurately estimate this effect.

Simulating potential outbreaks of Delta and Omicron variants based on contact-tracing data: A modelling study in Fujian Province, China.

Although studies have compared the relative severity of Omicron and Delta variants by assessing the relative risks, there are still gaps in the knowledge of the potential COVID-19 burden these variations may cause. And the contact patterns in Fujian Province, China, have not been described. We identified 8969 transmission pairs in Fujian, China, by analyzing a contact-tracing database that recorded a SARS-CoV-2 outbreak in September 2021. We estimated the waning vaccine effectiveness against Delta variant infection, contact patterns, and epidemiology distributions, then simulated potential outbreaks of Delta and Omicron variants using a multi-group mathematical model. For instance, in the contact setting without stringent lockdowns, we estimated that in a potential Omicron wave, only 4.7% of infections would occur in Fujian Province among individuals aged >60 years. In comparison, 58.75% of the death toll would occur in unvaccinated individuals aged >60 years. Compared with no strict lockdowns, combining school or factory closure alone reduced cumulative deaths of Delta and Omicron by 28.5% and 6.1%, respectively. In conclusion, this study validates the need for continuous mass immunization, especially among elderly aged over 60 years old. And it confirms that the effect of lockdowns alone in reducing infections or deaths is minimal. However, these measurements will still contribute to lowering peak daily incidence and delaying the epidemic, easing the healthcare system's burden.

Impact of public health and social measures on contact dynamics during a SARS-CoV-2 Omicron variant outbreak in Quanzhou, China, March to April 2022.

OBJECTIVES: To evaluate the impact of early implementation of public health and social measures (PHSMs) on contact rates over time and explore contact behavior of asymptomatic versus symptomatic cases. METHODS: We used the largest contact tracing data in China thus far to estimate the mean contacts over time by age groups and contact settings. We used bootstrap with replacement to quantify the uncertainty of contact matrixes. The Pearson correlation was performed to demonstrate the number of contacts over time in relation to the evolution of restrictions. In addition, we analyzed the index cases with a high number of contacts and index cases that produced a high number of secondary cases. RESULTS: Rapidly adapted PHSMs can reduce the mean contact rates in public places while increasing the mean contact rates within households. The mean contact rates were 11.81 (95% confidence interval, 11.61-12.01) for asymptomatic (at the time of investigation) cases and 6.70 (95% confidence interval, 6.54-6.87) for symptomatic cases. The percentage of asymptomatic cases (at the time of investigation) meeting >50 close contacts make up more than 65% of the overall cases. The percentage of asymptomatic cases producing >10 secondary cases account for more than 80% of the overall cases. CONCLUSION: PHSMs may increase the contacts within the household, necessitating the need for pertinent prevention strategies at home. Asymptomatic cases can contribute significantly to Omicron transmission. By making asymptomatic people aware that they are already contagious, hence limiting their social contacts, it is possible to lower the transmission risk.

Inactivated vaccine effectiveness against symptomatic COVID-19 in Fujian, China during the Omicron BA.2 outbreak.

Objective: More than 90% of the Chinese population have completed 2 doses of inactivated COVID-19 vaccines in Mainland China. However, after China government abandoned strict control measures, many breakthrough infections appeared, and vaccine effectiveness against Omicron BA.2 infection was uncertain. This study aims to investigate the real-world effectiveness of widely used inactivated vaccines during the wave of Omicron variants. Methods: Test-negative case-control study was conducted in this study to analyze the vaccine effectiveness against symptomatic disease caused by the Omicron variant (BA.2) in Fujian, China. Conditional logistic regression was selected to estimate the vaccine effectiveness. Results: The study found the vaccine effectiveness against symptomatic COVID-19 is 32.46% (95% CI, 8.08% to 50.37%) at 2 to 8 weeks, and 27.05% (95% CI, 1.23% to 46.12%) at 12 to 24 weeks after receiving booster doses of the inactivated vaccine. Notably, the 3-17 years group had higher vaccine effectiveness after 2 doses than the 18-64 years and over 65 years groups who received booster doses. Conclusion: Inactivated vaccines alone may not offer sufficient protection for all age groups before the summer of 2022. To enhance protection, other types of vaccines or bivalent vaccines should be considered.

Modelling the Emerging COVID-19 Epidemic and Estimating Intervention Effectiveness - Taiwan, China, 2021.

INTRODUCTION: The coronavirus disease 2019 (COVID-19) pandemic recently affected Taiwan, China. This study aimed to calculate the transmissibility of COVID-19 to predict trends and evaluate the effects of interventions. METHODS: The data of reported COVID-19 cases was collected from April 20 to May 26, 2021, which included daily reported data (Scenario I) and reported data after adjustment (Scenario II). A susceptible-exposed-symptomatic-asymptomatic-recovered model was developed to fit the data. The effective reproductive number (Reff ) was used to estimate the transmissibility of COVID-19. RESULTS: A total of 4,854 cases were collected for the modelling. In Scenario I, the intervention has already taken some effects from May 17 to May 26 (the Reff reduced to 2.1). When the Reff was set as 0.1, the epidemic was projected to end on July 4, and a total of 1,997 cases and 855 asymptomatic individuals would have been reported. In Scenario II, the interventions were projected as having been effective from May 24 to May 26 (the Reff reduced to 0.4). When the Reff was set as 0.1, the epidemic was projected to end on July 1, and a total of 1,482 cases and 635 asymptomatic individuals would have been reported. CONCLUSION: The epidemic of COVID-19 was projected to end after at least one month, even if the most effective interventions were applied in Taiwan, China. Although there were some positive effects of intervention in Taiwan, China.

Evaluating the importation of yellow fever cases into China in 2016 and strategies used to prevent and control the spread of the disease.

During the yellow fever epidemic in Angola in 2016, cases of yellow fever were reported in China for the first time. The 11 cases, all Chinese nationals returning from Angola, were identified in March and April 2016, one to two weeks after the peak of the Angolan epidemic. One patient died; the other 10 cases recovered after treatment. This paper reviews the epidemiological characteristics of the 11 yellow fever cases imported into China. It examines case detection and disease control and surveillance, and presents recommendations for further action to prevent additional importation of yellow fever into China.

Infectivity of severe acute respiratory syndrome during its incubation period.

OBJECTIVE: To evaluate the infectivity of severe acute respiratory syndrome (SARS) during its incubation period by investigating chains of transmission and individuals isolated for medical observation with a view to providing scientific evidence for updating protocols of medical isolation. METHODS: Individuals related with the two SARS chains of transmission in Beijing in 2003 and a group of individuals isolated for medical observation in Haidian district of Beijing during the SARS outbreak were selected as subjects of study. Contactors with SARS patients and those with symptom development following the contacts were investigated via questionnaire. Serum samples were collected from super transmitters and tested for SARS-CoV antibody by neutralization test and enzyme linked immunosorbent assay (ELISA). RESULTS: A total of 1112 contactors were investigated in three surveys. Of them, 669 had a history of close contact with symptomatic SARS patients, 101 developed symptoms with a rate of 15.1%, 363 had a history of close contact with patients in their incubation period, none of whom developed symptoms (0%). Serum samples were collected from 32 highly-exposed individuals, of whom 13 developing SARS symptoms after contact had serum samples positive for SARS-CoV antibody. Samples collected from the asymptomatic contactors were all negative for SARS-CoV antibody. CONCLUSION: SARS cases are infectious only during their symptomatic period and are non-infectious during the incubation period. Isolation for medical observation should be placed for individuals who are in close contact with symptomatic SARS patients. The results of our study are of decisive significance for the Ministry of Health to the definition of SARS close contactor.

A cluster-randomized controlled trial evaluating the effect of a handwashing-promotion program in Chinese primary schools.

Intensive handwashing promotion can reduce diarrheal and respiratory disease incidence. To determine whether less intensive, more scalable interventions can improve health, we evaluated a school-based handwashing program. We randomized 87 Chinese schools to usual practices: standard intervention (handwashing program) or expanded intervention (handwashing program, soap for school sinks, and peer hygiene monitors). We compared student absence rates, adjusting for cluster design. In control schools, children experienced a median 2.0 episodes (median 2.6 days) of absence per 100 student-weeks. In standard intervention schools, there were a median 1.2 episodes (P = 0.08) and 1.9 days (P = 0.14) of absence per 100 student-weeks. Children in expanded intervention schools experienced a median 1.2 episodes (P = 0.03) and 1.2 days (P = 0.03) of absence per 100 student-weeks. Provision of a large-scale handwashing promotion program and soap was associated with significantly reduced absenteeism. Similar programs could improve the health of children worldwide.

Epidemiological, clinical, and virologic features of two family clusters of avian influenza A (H7N9) virus infections in Southeast China.

This study aimed to investigate the epidemiological, clinical, and virologic characteristics of avian influenza A (H7N9) confirmed cases from two family clusters in Southeast China. Epidemiological data of the H7N9 confirmed cases and their close contacts were obtained through interviews and reviews of medical records. Of the four patients in these two family clusters, two cases had mild symptoms, one had severe symptoms, and one died. Three of the four patients had a history of exposure to live poultry or contaminated environments. The complete genome sequences of the H7N9 viruses from the same family cluster were highly homologous, and the four isolated viruses from the two family clusters exhibited the virologic features of the H7N9 virus, in terms of transmissibility, pathogenicity, host adaptation, and antiviral drug resistance. In addition, our findings indicated that the A/Fujian/18/2015 viral strain contained an additional hemagglutinin G225D substitution, which preferentially binds α2,6-linked sialic acids. The results of this study demonstrate that one family cluster was infected through common exposure to live poultry or contaminated environments, and the other was more likely to be infected through the human-to-human route.

Epidemiology of avian influenza A H7N9 virus in human beings across five epidemics in mainland China, 2013-17: an epidemiological study of laboratory-confirmed case series.

BACKGROUND: The avian influenza A H7N9 virus has caused infections in human beings in China since 2013. A large epidemic in 2016-17 prompted concerns that the epidemiology of the virus might have changed, increasing the threat of a pandemic. We aimed to describe the epidemiological characteristics, clinical severity, and time-to-event distributions of patients infected with A H7N9 in the 2016-17 epidemic compared with previous epidemics. METHODS: In this epidemiological study, we obtained information about all laboratory-confirmed human cases of A H7N9 virus infection reported in mainland China as of Feb 23, 2017, from an integrated electronic database managed by the China Center for Disease Control and Prevention (CDC) and provincial CDCs. Every identified human case of A H7N9 virus infection was required to be reported to China CDC within 24 h via a national surveillance system for notifiable infectious diseases. We described the epidemiological characteristics across epidemics, and estimated the risk of death, mechanical ventilation, and admission to the intensive care unit for patients admitted to hospital for routine clinical practice rather than for isolation purpose. We estimated the incubation periods, and time delays from illness onset to hospital admission, illness onset to initiation of antiviral treatment, and hospital admission to death or discharge using survival analysis techniques. FINDINGS: Between Feb 19, 2013, and Feb 23, 2017, 1220 laboratory-confirmed human infections with A H7N9 virus were reported in mainland China, with 134 cases reported in the spring of 2013, 306 in 2013-14, 219 in 2014-15, 114 in 2015-16, and 447 in 2016-17. The 2016-17 A H7N9 epidemic began earlier, spread to more districts and counties in affected provinces, and had more confirmed cases than previous epidemics. The proportion of cases in middle-aged adults increased steadily from 41% (55 of 134) to 57% (254 of 447) from the first epidemic to the 2016-17 epidemic. Proportions of cases in semi-urban and rural residents in the 2015-16 and 2016-17 epidemics (63% [72 of 114] and 61% [274 of 447], respectively) were higher than those in the first three epidemics (39% [52 of 134], 55% [169 of 306], and 56% [122 of 219], respectively). The clinical severity of individuals admitted to hospital in the 2016-17 epidemic was similar to that in the previous epidemics. INTERPRETATION: Age distribution and case sources have changed gradually across epidemics since 2013, while clinical severity has not changed substantially. Continued vigilance and sustained intensive control efforts are needed to minimise the risk of human infection with A H7N9 virus. FUNDING: The National Science Fund for Distinguished Young Scholars.

Protective Effect of Hand-Washing and Good Hygienic Habits Against Seasonal Influenza: A Case-Control Study.

Previous observational studies have reported protective effects of hand-washing in reducing upper respiratory infections, little is known about the associations between hand-washing and good hygienic habits and seasonal influenza infection. We conducted a case-control study to test whether the risk of influenza transmission associated with self-reported hand-washing and unhealthy hygienic habits among residents in Fujian Province, southeastern China.Laboratory confirmed seasonal influenza cases were consecutively included in the study as case-patients (n = 100). For each case, we selected 1 control person matched for age and city of residence. Telephone interview was used to collect information on hand-washing and hygienic habits. The associations were analyzed using conditional logistic regression. Compared with the poorest hand-washing score of 0 to 3, odds ratios of influenza infection decreased progressively from 0.26 to 0.029 as hand-washing score increased from 4 to the maximum of 9 (P < 0.001). Compared with the poorest hygienic habit score of 0 to 2, odds ratios of influenza infection decreased from 0.10 to 0.015 with improving score of hygienic habits (P < 0.001). Independent protective factors against influenza infection included good hygienic habits, higher hand-washing score, providing soap or hand cleaner beside the hand-washing basin, and receiving influenza vaccine. Regular hand-washing and good hygienic habits were associated with a reduced risk of influenza infection. These findings support the general recommendation for nonpharmaceutical interventions against influenza.

[Role of syndromic surveillance program in the practice of early detection on disease outbreak].

OBJECTIVE: A Dengue outbreak was reported in Dongfen town Jianou county, Fujian province on September 19, 2014. The goal of this project was to explore the role of syndromic surveillance program in the practice of early detection on disease outbreak through the case mentioned above. METHODS: The authors retrospectively collected data related to Outpatient log and Pharmacy drug use in Dongfen township hospital through the electronic information system of the hospital from August to November, 2014. All the abnormal events were recorded, according to related data on fever and drug use. Description of fever, syndromic characteristics, correlation and Linear regression analyses were conducted, using the surveillance data on fever syndrome and drug use from the pharmacy. RESULTS: A total of 1 102 cases with fever and 2 437 fever-related clinic visits were reported which showing an increased number of 19.6, 10.2 times respectively, when compared to the same period of the previous year in which men accounted for 45.3% (499/1 102) and female accounted for 54.7% (603/1 102). Age groups presented an atypical type " M" type. 5 and 10 year olds groups formed the largest proportion, accounted for 11.5% (127/1 102) of the total number os the patients. The correlation coefficient ranged from 0.85 to 0.97 (P<0.05). Data from the syndromic surveillance program showed an " outbreak" was occured in August 23, 2014. CONCLUSIONS: Compared to routine surveillance program, the syndromic surveillance program could detect the appearence of an outbreak, a month or even more earlier. The role of syndromic surveillance program needs to be further explored.

Risk Factors for Influenza A(H7N9) Disease in China, a Matched Case Control Study, October 2014 to April 2015.

Background. Human infections with avian influenza A(H7N9) virus have been associated with exposure to poultry and live poultry markets (LPMs). We conducted a case-control study to identify additional and more specific risk factors. Methods. Cases were laboratory-confirmed A(H7N9) infections in persons in China reported from October 1, 2014 to April 30, 2015. Poultry workers, those with insufficient data, and those refusing participation were excluded. We matched up to 4 controls per case by sex, age, and residential community. Using conditional logistic regression, we examined associations between A(H7N9) infection and potential risk factors. Results. Eighty-five cases and 334 controls were enrolled with similar demographic characteristics. Increased risk of A(H7N9) infection was associated with the following: visiting LPMs (adjusted odds ratio [aOR], 6.3; 95% confidence interval [CI], 2.6-15.3), direct contact with live poultry in LPMs (aOR, 4.1; 95% CI, 1.1-15.6), stopping at a live poultry stall when visiting LPMs (aOR, 2.7; 95% CI, 1.1-6.9), raising backyard poultry at home (aOR, 7.7; 95% CI, 2.0-30.5), direct contact with backyard poultry (aOR, 4.9; 95% CI, 1.1-22.1), and having ≥1 chronic disease (aOR, 3.1; 95% CI, 1.5-6.5). Conclusions. Our study identified raising backyard poultry at home as a risk factor for illness with A(H7N9), suggesting the need for enhanced avian influenza surveillance in rural areas.

[Epidemiological study of the transmission chain of a severe acute respiratory syndrome outbreak].

OBJECTIVE: To investigate the process of SARS transmission and to evaluate infectivity of SARS patients in different periods of disease development. METHODS: A case of SARS outbreak beginning from a male, 74-year-old patient in Beijing. Two hundred and seventy five primary, secondary and tertiary contacts, including family members relatives, colleagues, and others exposed to him, were traced by field investigation and telephone interview using a standardized questionnaire. The transmission process and infectivity of disease were analyzed with transmission chain diagram and contact history diagram. RESULTS: Among the 275 contacts of the index case, 41 fell ill of SARS with an attack rate of 14.9% and 5 deaths with a fatality rate of 12.2%. The transmission chain of this outbreak could be clearly delineated, and all the 41 cases had close contacts with their infectors, SARS cases of the previous generation within the symptomatic period thereof. All of the 114 contacts that contacted their infectors, SARS cases of the previous generation during the incubation period thereof remained healthy. The incubation period of 27 cases that had contacted their infectors only once was 1 - 10 days with a median of 3 days. The highest risk of being infected was caring the patients unprotectedly, followed by living together with patient, visiting patient, and handling patient without protection. CONCLUSION: All the secondary cases have the history of close contact with their symptomatic infectors of previous generation. It cannot be proved at all that SARS is infective during the incubation period. The infectivity of SARS is related to the degree of closeness of contact with the patient.