China ; Humans ; Infectious Disease Incubation Period ; Pneumoconiosis

BACKGROUND: A sputum culture is the most reliable indicator of the infectiousness of pulmonary tuberculosis (PTB); however, a spontaneous sputum specimen may not be suitable. The aim of this study was to evaluate the infectious period in patients with non–drug-resistant (DR) PTB receiving adequate standard chemotherapy, using induced sputum (IS) specimens. METHODS: We evaluated the duration of infectiousness of PTB using a retrospective cohort design. RESULTS: Among the 35 patients with PTB, 22 were smear-positive. The rates of IS culture positivity from baseline to the sixth week of anti-tuberculosis medication in the smear-positive PTB group were 100%, 100%, 91%, 73%, 36%, and 18%, respectively. For smear-positive PTB cases, the median time of conversion to culture negativity was 35.0 days (range, 28.0–42.0 days). In the smear-negative PTB group (n=13), the weekly rates of positive IS culture were 100%, 77%, 39%, 8%, 0%, and 0%, respectively, and the median time to conversion to culture-negative was 21.0 days (range, 17.5–28.0 days). CONCLUSION: The infectiousness of PTB, under adequate therapy, may persist longer than previously reported, even in patients with non-DR PTB.
Cohort Studies ; Drug Therapy ; Humans ; Infectious Disease Incubation Period ; Mycobacterium tuberculosis ; Retrospective Studies ; Sputum* ; Tuberculosis, Pulmonary*

Animals ; Humans ; Infectious Disease Incubation Period ; Malaria, Vivax ; epidemiology ; parasitology ; Plasmodium vivax ; pathogenicity

OBJECTIVETo 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.

METHODSIndividuals 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).

RESULTSA 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.

CONCLUSIONSARS 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.

China ; epidemiology ; Disease Outbreaks ; Humans ; Infectious Disease Incubation Period ; SARS Virus ; physiology ; Severe Acute Respiratory Syndrome ; epidemiology ; transmission ; virology

Objective: To study the incubation period of the infection with 2019-nCoV Omicron variant BA.5.1.3. Methods: Based on the epidemiological survey data of 315 COVID-19 cases and the characteristics of interval censored data structure, log-normal distribution and Gamma distribution were used to estimate the incubation. Bayes estimation was performed for the parameters of each distribution function using discrete time Markov chain Monte Carlo algorithm. Results: The mean age of the 315 COVID-19 cases was (42.01±16.54) years, and men accounted for 30.16%. A total of 156 cases with mean age of (41.65±16.32) years reported the times when symptoms occurred. The log-normal distribution and Gamma distribution indicated that the M (Q₁, Q₃) of the incubation period from exposure to symptom onset was 2.53 (1.86, 3.44) days and 2.64 (1.91, 3.52) days, respectively, and the M (Q₁, Q₃) of the incubation period from exposure to the first positive nucleic acid detection was 2.45 (1.76, 3.40) days and 2.57 (1.81, 3.52) days, respectively. Conclusions: The incubation period by Bayes estimation based on log-normal distribution and Gamma distribution, respectively, was similar to each other, and the best distribution of incubation period was Gamma distribution, the difference between the incubation period from exposure to the first positive nucleic acid detection and the incubation period from exposure to symptom onset was small. The median of incubation period of infection caused by Omicron variant BA.5.1.3 was shorter than those of previous Omicron variants.
Male ; Humans ; Adult ; Middle Aged ; SARS-CoV-2 ; COVID-19 ; Bayes Theorem ; Infectious Disease Incubation Period ; Nucleic Acids

BACKGROUND: Current studies on the COVID-19 depicted a general incubation period distribution and did not examine whether the incubation period distribution varies across patients living in different geographical locations with varying environmental attributes. Profiling the incubation distributions geographically help to determine the appropriate quarantine duration for different regions. METHODS: This retrospective study mainly applied big data analytics and methodology, using the publicly accessible clinical report for patients (n = 543) confirmed as infected in Shenzhen and Hefei, China. Based on 217 patients on whom the incubation period could be identified by the epidemiological method. Statistical and econometric methods were employed to investigate how the incubation distributions varied between infected cases reported in Shenzhen and Hefei. RESULTS: The median incubation period of the COVID-19 for all the 217 infected patients was 8 days (95% CI 7 to 9), while median values were 9 days in Shenzhen and 4 days in Hefei. The incubation period probably has an inverse U-shaped association with the meteorological temperature. The warmer condition in the winter of Shenzhen, average environmental temperature between 10 °C to 15 °C, may decrease viral virulence and result in more extended incubation periods. CONCLUSION Case studies of the COVID-19 outbreak in Shenzhen and Hefei indicated that the incubation period of COVID-19 had exhibited evident geographical disparities, although the pathological causality between meteorological conditions and incubation period deserves further investigation. Methodologies based on big data released by local public health authorities are applicable for identifying incubation period and relevant epidemiological research.
Adolescent ; Adult ; Aged ; COVID-19/prevention & control* ; Child ; China/epidemiology* ; Female ; Geography ; Humans ; Infectious Disease Incubation Period ; Male ; Middle Aged ; Quarantine ; Retrospective Studies ; SARS-CoV-2 ; Young Adult

Objective: To estimate the latent period and incubation period of Omicron variant infections and analyze associated factors. Methods: From January 1 to June 30, 2022, 467 infections and 335 symptomatic infections in five local Omicron variant outbreaks in China were selected as the study subjects. The latent period and incubation period were estimated by using log-normal distribution and gamma distribution models, and the associated factors were analyzed by using the accelerated failure time model (AFT). Results: The median (Q₁, Q₃) age of 467 Omicron infections including 253 males (54.18%) was 26 (20, 39) years old. There were 132 asymptomatic infections (28.27%) and 335 (71.73%) symptomatic infections. The mean latent period of 467 Omicron infections was 2.65 (95%CI: 2.53-2.78) days, and 98% of infections were positive for nucleic acid test within 6.37 (95%CI: 5.86-6.82) days after infection. The mean incubation period of 335 symptomatic infections was 3.40 (95%CI: 3.25-3.57) days, and 97% of them developed clinical symptoms within 6.80 (95%CI: 6.34-7.22) days after infection. The results of the AFT model analysis showed that compared with the group aged 18-49 years old, the latent period [exp(β)=1.36 (95%CI: 1.16-1.60), P<0.001] and incubation period [exp(β)=1.24 (95%CI: 1.07-1.45), P=0.006] of infections aged 0-17 years old were prolonged. The latent period [exp(β)=1.38 (95%CI: 1.17-1.63), P<0.001] and the incubation period [exp(β)=1.26 (95%CI: 1.06-1.48), P=0.007] of infections aged 50 years old and above were also prolonged. Conclusion: The latent period and incubation period of most Omicron infections are within 7 days, and age may be a influencing factor of the latent period and incubation period.
Male ; Humans ; Adult ; Adolescent ; Young Adult ; Middle Aged ; Infant, Newborn ; Infant ; Child, Preschool ; Child ; COVID-19 ; SARS-CoV-2 ; Infectious Disease Incubation Period ; Asymptomatic Infections

OBJECTIVETo develop a new transmission tracking analysis technique during incubation period of respiratory infectious diseases, and to discuss its practical value in the field survey of infectious diseases.

METHODSThe classical epidemiological theory was integrated with geographic information system. The transmission tracking analysis technique was established based on the modeling platform ArcGIS Engine Developer Kit 9.3, using the techniques of address matching, shortest path analysis and buffer analysis, and programming by Visual C++. Eight serious sever acute respiratory syndrome (SARS) cases in Shanghai in year 2003 were then chose as prototype to set up the test cases A-H. The electronic map and population density data were separately collected from Institute of Surveying and Mapping in Shanghai and Shanghai statistical yearbook 2003, to calculate and explore the parameters as length of transmission path, area of buffer zone and key departments by single and multi case analysis module.

RESULTSThe single case transmission tracking analysis showed that the length of transmission track of case A was 129.89 km during April 25th to 29th in 2003, including 12 tracing point and 108 intimate contacts, and the total area of buffer zone was 7.11 km(2) including 81 important institutes, naming 72 schools, 6 kindergartens and 3 gerocomiums. The multi-case transmission tracking analysis showed that the 8 cases shared 5 tracks without any temporal communication. However, there was a spatial communication whose length was 1.42 km and area was 0.60 km(2). There were no important institutes found in this communication area.

CONCLUSIONTransmission tracking technique is practicable and efficient to trace the source of infection, analyze the transmission tracks, establish the isolation buffer area and explore the important geographic positions in epidemiological investigation.

Contact Tracing ; methods ; Disease Transmission, Infectious ; statistics & numerical data ; Epidemiological Monitoring ; Geographic Information Systems ; Humans ; Infectious Disease Incubation Period ; Respiratory Tract Infections ; transmission ; Severe Acute Respiratory Syndrome ; transmission ; Software

OBJECTIVEDiscussing the natural history and the influencing factors of HIV infection among former commercial blood and plasma donors engaged in unsafe blood donation practices in China.

METHODSUsing ambispective cohort study, with data obtained from ten counties (districts) from six provinces in the National AIDS Control Demonstration Area. HIV/AIDS cases were found and confirmed prior to July 24, 2006 being former commercial blood. Plasma donors were selected and data regarding infection, incidence, death, and influencing factors was collected. Analysis was performed using SPSS 12.0 statistical analysis software.

RESULTS(1) In 7551 cases of HIV infection, there were 6533 typical progressors (86.52%, 4757 cases of AIDS), 108 rapid progressors (1.43%), 910 long-term non-progressors (12.05%) with 4865 cases progressed to AIDS (64.43%). The median incubation period for HIV progression to AIDS was nine years (95% CI:8.96-9.04). (2) According to data, from a total of 1157 AIDS cases without ARV therapy (23.78% of total AIDS cases), there were 283 confirmed AIDS-related deaths, of which the median survival time was 6 months (95% CI:4-7) and the two and three year fatality rates were 95% and 99%, respectively. (3) The duration of HIV incubation period was irrespective to gender and age at the time of HIV infection (P > 0.05). Length of survival for untreated AIDS showed correlation to gender (P < 0.05) but no correlation with culture, marital status or age at the time of diagnosis of AIDS (P > 0.05).

CONCLUSIONCompared with the UNAIDS theory regarding slow disease progressors among adults, our study showed a longer AIDS incubation period and shorter outlook for untreated survival, but a similar incubation period for other routes of HIV infection.

Acquired Immunodeficiency Syndrome ; epidemiology ; mortality ; Adolescent ; Adult ; Aged ; Blood Donors ; statistics & numerical data ; China ; Female ; HIV Infections ; epidemiology ; mortality ; Humans ; Infectious Disease Incubation Period ; Male ; Middle Aged ; Young Adult

Through literature review and group discussion, Special Expert Group for Control of the Epidemic of Novel Coronavirus Pneumonia of the Chinese Preventive Medicine Association formulated an update on the epidemiological characteristics of novel coronavirus pneumonia (NCP). The initial source of the 2019 novel coronavirus (2019-nCoV) was the Huanan seafood market in Wuhan, Hubei province, China, with pangolins as a potential animal host. Currently the main source of infection is NCP patients, and asymptomatic carriers may also be infectious. The virus is believed transmitted mostly via droplets or contact. People are all generally susceptible to the virus. The average incubation period was 5.2 days, and the basic reproductive number R(0) was 2.2 at the onset of the outbreak. Most NCP patients were clinically mild cases. The case fatality rate was 2.38%, and elderly men with underlying diseases were at a higher risk of death. Strategies for prevention and control of NCP include improving epidemic surveillance, quarantining the source of infection, speeding up the diagnosis of suspected cases, optimizing the management of close contacts, tightening prevention and control of cluster outbreaks and hospital infection, preventing possible rebound of the epidemic after people return to work from the Chinese Spring Festival holiday, and strengthening community prevention and control.
Aged ; Animals ; Asymptomatic Diseases/epidemiology* ; Betacoronavirus ; COVID-19 ; China/epidemiology* ; Contact Tracing ; Coronavirus ; Coronavirus Infections/epidemiology* ; Humans ; Infectious Disease Incubation Period ; Male ; Pandemics ; Pneumonia, Viral/epidemiology* ; Public Health Surveillance/methods* ; Quarantine ; SARS-CoV-2