On the study of full transmission dynamics of COVID-19 in Wuhan

Abstract The current outbreak of coronavirus disease 2019 (COVID-19) has quickly spread across countries and become a global crisis. Understanding the transmission mechanism and effects of interventions is critical to the prevention and control of the COVID-19 pandemic. A recent study by Hao et al (2020) provided an interesting perspective on the transmission dynamics of COVID-19 in Wuhan and inferred that 87% of the infections before 8 March 2020 were not laboratory-confirmed. However we believe that there are a few major issues due to the vagueness in the definitions of compartments and inconsistence in the settings of parameters. In this paper, we clarify the definitions of the model compartments and raise questions in regard to the underlying homogenous assumption within compartments and settings of the parameters in the dynamic model by Hao et al (2020), and furthermore offer a modified model to resolve these potential limitations. Compared with the model in Hao et al (2020), the active virus carriers were predicted to persist for a longer period in our model which is well consistent with the active virus carriers detected in Wuhan in mid-May. Our model suggests that control measures cannot be easily lifted while continuous efforts are needed to contain the spread of the pandemic; a universal PT-PCR screening is essential to detect hidden cases before lifting control measure. In addition, we also provide a possible solution to solve the problem of heterogeneity transmission rate in disease courses.

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Indices of Land Degradation and Control Measures in Selected Urban Communities of Abeokuta, Ogun State, Nigeria

International Journal of Social Ecology and Sustainable Development ◽

10.4018/ijsesd.2015100104 ◽

2015 ◽

Vol 6 (4) ◽

pp. 54-66

Author(s):

O. A. Lawal-Adebowle ◽

A. K. Aromolaran

Keyword(s):

Urban Communities ◽

Land Degradation ◽

Urban Areas ◽

Control Measure ◽

Drainage System ◽

Control Measures ◽

Causal Factors ◽

Ogun State ◽

And Control ◽

Observational Techniques

The study assessed the causal factors of land degradation in urban areas of Abeokuta and the employed control measures by residents of the communities. A qualitative approach, which encompasses observational techniques – participant/field observation, interactive discussion and photographic capturing, was used for collection of data on land degradation in the study area. Analysis of collected data showed land gradients, rainfall and run-offs, erosion, entrenched foot paths, sand scraping/mining, poor/absence of drainage system and land covers as causal factors of land degradation in the study area. The study though observed that control measures such as filling of drenches with sand bags, wood logs, bricks and stones were employed by residents in the study area, construction of good drainage system was presumed to be the most appropriate and sustainable control measure of water erosion in the study area.

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Measles outbreak: preliminary report on a case series of the first 8,070 suspected cases, Manaus, Amazonas state, Brazil, February to November 2018

Eurosurveillance ◽

10.2807/1560-7917.es.2019.24.2.1800663 ◽

2019 ◽

Vol 24 (2) ◽

Cited By ~ 6

Author(s):

Guilherme Almeida Elidio ◽

Giovanny Vinícius Araújo de França ◽

Flávia Caselli Pacheco ◽

Marinélia Martins Ferreira ◽

Jair dos Santos Pinheiro ◽

...

Keyword(s):

Measles Virus ◽

Vaccine Coverage ◽

Case Series ◽

Control Measures ◽

Measles Outbreak ◽

Current Scenario ◽

Current Outbreak ◽

Prevention And Control Measures ◽

Amazonas State ◽

And Control

We report an ongoing measles outbreak in Manaus, Amazonas state, Brazil. As at 3 November 2018, 1,631 cases were confirmed corresponding to an incidence of 75.3 per 100,000 inhabitants; all five sanitary districts presented confirmed cases. Reintroduction of measles virus in Manaus is likely related to the current outbreak in Venezuela and due to recent decline in measles vaccine coverage. Given the current scenario, prevention and control measures should target individuals aged 15–29 years.

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Modeling the Novel Coronavirus (SARS-CoV-2) Outbreak in Sicily, Italy

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17144964 ◽

2020 ◽

Vol 17 (14) ◽

pp. 4964 ◽

Cited By ~ 5

Author(s):

Andrea Maugeri ◽

Martina Barchitta ◽

Sebastiano Battiato ◽

Antonella Agodi

Keyword(s):

Transmission Rate ◽

Control Measures ◽

Transmission Dynamics ◽

The Novel ◽

Epidemic Spread ◽

Transmission Rates ◽

Contact Precautions ◽

Travel Restrictions ◽

Novel Coronavirus ◽

Reported Data

Italy was the first country in Europe which imposed control measures of travel restrictions, quarantine and contact precautions to tackle the epidemic spread of the novel coronavirus (SARS-CoV-2) in all its regions. While such efforts are still ongoing, uncertainties regarding SARS-CoV-2 transmissibility and ascertainment of cases make it difficult to evaluate the effectiveness of restrictions. Here, we employed a Susceptible-Exposed-Infectious-Recovered-Dead (SEIRD) model to assess SARS-CoV-2 transmission dynamics, working on the number of reported patients in intensive care unit (ICU) and deaths in Sicily (Italy), from 24 February to 13 April. Overall, we obtained a good fit between estimated and reported data, with a fraction of unreported SARS-CoV-2 cases (18.4%; 95%CI = 0–34.0%) before 10 March lockdown. Interestingly, we estimated that transmission rate in the community was reduced by 32% (95%CI = 23–42%) after the first set of restrictions, and by 80% (95%CI = 70–89%) after those adopted on 23 March. Thus, our estimates delineated the characteristics of SARS-CoV2 epidemic before restrictions taking into account unreported data. Moreover, our findings suggested that transmission rates were reduced after the adoption of control measures. However, we cannot evaluate whether part of this reduction might be attributable to other unmeasured factors, and hence further research and more accurate data are needed to understand the extent to which restrictions contributed to the epidemic control.

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A STUDY OF SCHISTOSOME TRANSMISSION DYNAMICS AND ITS CONTROL

Journal of Biological System ◽

10.1142/s0218339006001799 ◽

2006 ◽

Vol 14 (02) ◽

pp. 295-302 ◽

Cited By ~ 2

Author(s):

PRASENJIT DAS ◽

DEBASIS MUKHERJEE ◽

A. K. SARKAR

Keyword(s):

Numerical Simulations ◽

Mathematical Analysis ◽

Control Measure ◽

Model Analysis ◽

Unstable Equilibrium ◽

Control Measures ◽

Transmission Dynamics ◽

Delay Effect

This article concentrates on the study of delay effect on a model of schistosomiasis transmission with control measures such as predation or harvesting and chemotherapy. In the presence of predation or harvesting and chemotherapy, system admits multiple endemic equilibria. Mathematical analysis shows that they are opposite in nature regarding stability. One may observe switching phenomena for the unstable equilibrium by incorporating delay. The disease may be highly endemic if there is no control measure, which is obvious from the model analysis. Results obtained in this paper are also verified through numerical simulations.

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The Spatial-Temporal Distribution and Control Measures Evaluation of Droplets and Aerosol Cloud in Dental Procedures

10.21203/rs.3.rs-641159/v1 ◽

2021 ◽

Author(s):

Chao Yuan ◽

Hongtao Yang ◽

Siyuan Zheng ◽

Xiangyu Sun ◽

Xiaochi Chen ◽

...

Keyword(s):

High Speed ◽

Control Measure ◽

Operation Mode ◽

Temporal Distribution ◽

High Volume ◽

Control Measures ◽

Aerosol Cloud ◽

Dental Procedures ◽

Air Purifier ◽

And Control

Abstract Background: Droplets and aerosol cloud generating procedures in dentistry can increase the risk of airborne transmission of diseases such as COVID-19. To gain insight into the diffusion of spatters and possible preventive measures, we measured the particle spatial-temporal distribution characteristic and evaluated the effectiveness of the control measures.Methods: We conducted an experiment to observe the emitted spatters obtained during the simulated dental preparation by using high-speed videography. We measured the particle size distributions by laser diffraction and preliminarily estimated its velocity. We qualitatively and quantitatively described the spatial-temporal distributions of spatters and their control measure effects. Results: Majority of the dental spatters were small droplets (diameter less than 50 μm). A large number of smallest droplets (diameter less than 10 μm) were generated by high-speed air turbine handpiece. At the oral outlet, the speed of large droplets could exceed 2.63 m/s, and the speed of aerosol clouds ranged from 0.31–2.37 m/s. The evolution of the spatters showed that the more fully developed the state, the greater the number of spatters and the wider the contamination range. When the operation mode was moved from the central incisor to the first molar, the spatter direction became increasingly concentrated, and the velocities were enhanced. Larger droplets randomly moved along trajectories and rapidly settled. The aerosol cloud tended to float as a mass that interacted with the surrounding air. The high-volume evacuation could effectively clear away most of the dental spatters. The suction air purifier could change the diffusion direction of the spatters, compress the contamination range, and control aerosol escape into surrounding air. Conclusions: Our view is that we should combine the ‘point’ control measure (high-volume evacuation) and ‘area’ control measure (suction air purifier) to reduce the scope of pollution and prevent the aerosol escape into the surroundings. The study contributes to devising more accurate infection control guidelines, establishing appropriate interventions for different oral treatments, and minimizing the spread of respiratory diseases so that we can reduce cost and achieve the best results when medical resources are limited.

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Assessing coughing-induced influenza droplet transmission and implications for infection risk control

Epidemiology and Infection ◽

10.1017/s0950268815001739 ◽

2015 ◽

Vol 144 (2) ◽

pp. 333-345 ◽

Cited By ~ 7

Author(s):

Y.-H. CHENG ◽

C.-H. WANG ◽

S.-H. YOU ◽

N.-H. HSIEH ◽

W.-Y. CHEN ◽

...

Keyword(s):

Respiratory Tract ◽

Risk Model ◽

Control Measure ◽

Influenza Infection ◽

Infection Risk ◽

Transmission Dynamics ◽

Human Respiratory Tract ◽

Host Interactions ◽

And Control ◽

Respiratory Droplets

SUMMARYIndoor transmission of respiratory droplets bearing influenza within humans poses high risks to respiratory function deterioration and death. Therefore, we aimed to develop a framework for quantifying the influenza infection risk based on the relationships between inhaled/exhaled respiratory droplets and airborne transmission dynamics in a ventilated airspace. An experiment was conducted to measure the size distribution of influenza-containing droplets produced by coughing for a better understanding of potential influenza spread. Here we integrated influenza population transmission dynamics, a human respiratory tract model, and a control measure approach to examine the indoor environment–virus–host interactions. A probabilistic risk model was implemented to assess size-specific infection risk for potentially transmissible influenza droplets indoors. Our results found that there was a 50% probability of the basic reproduction number (R0) exceeding 1 for small-size influenza droplets of 0·3–0·4 µm, implicating a potentially high indoor infection risk to humans. However, a combination of public health interventions with enhanced ventilation could substantially contain indoor influenza infection. Moreover, the present dynamic simulation and control measure assessment provide insights into why indoor transmissible influenza droplet-induced infection is occurring not only in upper lung regions but also in the lower respiratory tract, not normally considered at infection risk.

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Effectiveness of environmental decontamination as an infection control measure

Epidemiology and Infection ◽

10.1017/s0950268811000604 ◽

2011 ◽

Vol 140 (3) ◽

pp. 542-553 ◽

Cited By ~ 11

Author(s):

M. BANI-YAGHOUB ◽

R. GAUTAM ◽

D. DÖPFER ◽

C. W. KASPAR ◽

R. IVANEK

Keyword(s):

Infectious Diseases ◽

Infection Control ◽

Transmission Rate ◽

Control Measure ◽

Infection Control Measure ◽

Endemic Equilibrium ◽

Control Measures ◽

Duration Of Infection ◽

Environmental Decontamination ◽

Disease Free

SUMMARYThe effectiveness of environmental decontamination (ED) as a measure in the control of infectious diseases is controversial. This work quantifies the effectiveness of ED by analysing the transmission of pathogens from the environment to susceptible hosts in a Susceptible–Infected–Susceptible model. Analysis of the model shows that ED can render a population disease-free only when the duration of infection (D) is within a certain range. As host-to-host transmission rate is increased,Dfalls outside this range and the higher levels of ED have a diminishing return in reducing the number of infected hosts at endemic equilibrium. To avoid this, ED can be combined with other control measures, such as treating infected individuals to push the duration of infection into the specified range. We propose decision criteria and minimum ED efforts required for control policies to be effective.

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Exponential Damping: The Key to Successful Containment of COVID-19

Frontiers in Public Health ◽

10.3389/fpubh.2020.580619 ◽

2021 ◽

Vol 8 ◽

Author(s):

Feng Zhang ◽

Jinmei Zhang ◽

Menglan Cao ◽

Yong Zhang ◽

Cang Hui

Keyword(s):

Transmission Rate ◽

Public Health Emergency ◽

Control Measures ◽

Time Varying ◽

Global Public Health ◽

Damping Rate ◽

Negative Damping ◽

Entire World ◽

And Control ◽

Existing Data

Due to its excessive capacity for human-to-human transmission, the 2019 coronavirus disease (COVID-19) has now been declared a global public health emergency. Here we propose a simple model based on exponential infectious growth, but with a time-varying, largely damping, transmission rate. This model provides an excellent fit to the existing data for 46 countries with 10,000+ cases by 16 May 2020, five continents and the entire world. Hence, the model has largely captured the transmission patterns of the COVID-19 outbreak under a variety of intervention and control measures. The damping rate ranged from −0.0228 to 0.1669 d−1 globally (a negative damping rate represents acceleration in spread) and can greatly affect the duration of the outbreak and the eventual number of infections. Our model suggests that it is possible to defeat the COVID-19 pandemic by the end of 2020 through achieving a high damping rate (0.0615 d−1). However, the global damping rate is rather low (0.0504 d−1 before 26 April) and has dropped even further since late April (0.0168 d−1). Easing currently implemented control measures in countries with weak or no damping in transmission could lead to an exponential rebound of COVID-19 spread.

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Transmission Dynamics of Corynebacterium spp. Within Two Danish Dairy Cattle Herds

Frontiers in Veterinary Science ◽

10.3389/fvets.2021.735345 ◽

2021 ◽

Vol 8 ◽

Author(s):

Carsten Kirkeby ◽

Tariq Halasa ◽

Michael Farre ◽

Galal Nazih Chehabi ◽

Kaare Græsbøll

Keyword(s):

Dairy Cattle ◽

Transmission Rate ◽

Cost Effective ◽

Control Measures ◽

Transmission Dynamics ◽

Effective Control ◽

Indirect Transmission ◽

The Mean ◽

Cattle Herds ◽

Danish Dairy

Intramammary infections (IMI) can cause mastitis, a prevalent and costly infectious disease in dairy cattle worldwide. The IMI is caused by a range of bacteria, including Corynebacterium spp. Knowledge of the transmission dynamics of pathogens is generally sparse but essential to support decision-making; such as input to bioeconomic models. In this observational study, we explored the transmission dynamics of Corynebacterium spp. in two different Danish dairy cattle herds by testing monthly quarter-level milk samples of all lactating cows for 1 year. We estimated the prevalence for herd 1 and 2 to 24 and 11.7%, respectively, and the mean quarter-level incidence to be 8 and 6.5% per month, respectively. We compared a model for indirect transmission via the environment with a model with the direct contagious transmission and found that the latter model best explained the data. We estimated the daily mean quarter-level transmission rate to be 0.016 and 0.018 cases/quarter-day for herd 1 and 2, respectively. The mean recovery rate was 0.012 and 0.016 for herd 1 and 2, respectively. Consequently, the basic reproduction number for herd 1 and 2 was 1.27 and 1.10, respectively. This study highlights that Corynebacterium spp. can be prevalent within a herd and transmit directly between cows. Thus, future studies should investigate cost-effective control measures against Corynebacterium spp.

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