On the study of the dynamic model 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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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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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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Research about the optimal strategies for prevention and control of varicella outbreak in a school in a central city of China: based on an SEIR dynamic model

Epidemiology and Infection ◽

10.1017/s0950268819002188 ◽

2020 ◽

Vol 148 ◽

Cited By ~ 8

Author(s):

Wen-ting Zha ◽

Feng-rui Pang ◽

Nan Zhou ◽

Bin Wu ◽

Ying Liu ◽

...

Keyword(s):

Dynamic Model ◽

Prevention And Control ◽

Model Simulation ◽

Central City ◽

Control Measures ◽

Peak Time ◽

Cumulative Number ◽

And Control ◽

Epidemiological Characteristics ◽

Combined Interventions

Abstract Varicella is an acute respiratory infectious diseases, with high transmissibility and quick dissemination. In this study, an SEIR (susceptible-exposed-infected-recovered) dynamic model was established to explore the optimal prevention and control measures according to the epidemiological characteristics about varicella outbreak in a school in a central city of China. Berkeley Madonna 8.3.18 and Microsoft Office Excel 2010 software were employed for the model simulation and data management, respectively. The result showed that the simulated result of SEIR model agreed well with the reported data when β (infected rate) equal to 0.067. Models showed that the cumulative number of cases was only 13 when isolation adopted when the infected individuals were identified (assuming isolation rate was up to 100%); the cumulative number of cases was only two and the TAR (total attack rate) was 0.56% when the vaccination coefficient reached 50%. The cumulative number of cases did not change significantly with the change of efficiency of ventilation and disinfection, but the peak time was delayed; when δ (vaccination coefficient) = 0.1, m (ventilation efficiency) = 0.7 or δ = 0.2, m = 0.5 or δ = 0.3, m = 0.1 or δ = 0.4 and above, the cumulative number of cases would reduce to one case and TAR would reduce to 0.28% with combined interventions. Varicella outbreak in school could be controlled through strict isolation or vaccination singly; combined interventions have been adopted when the vaccination coefficient was low.

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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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Prediction of the COVID-19 outbreak in China based on a new stochastic dynamic model

Scientific Reports ◽

10.1038/s41598-020-76630-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Yuan Zhang ◽

Chong You ◽

Zhenhao Cai ◽

Jiarui Sun ◽

Wenjie Hu ◽

...

Keyword(s):

Dynamic Models ◽

Transmission Rate ◽

Mainland China ◽

Control Measures ◽

Stochastic Dynamic ◽

Epidemic Outbreak ◽

Intervention Measures ◽

Control And Prevention ◽

Current Outbreak ◽

Virus Carrier

AbstractThe current outbreak of coronavirus disease 2019 (COVID-19) has become a global crisis due to its quick and wide spread over the world. A good understanding of the dynamic of the disease would greatly enhance the control and prevention of COVID19. However, to the best of our knowledge, the unique features of the outbreak have limited the applications of all existing dynamic models. In this paper, a novel stochastic model was proposed aiming to account for the unique transmission dynamics of COVID-19 and capture the effects of intervention measures implemented in Mainland China. We found that: (1) instead of aberration, there was a remarkable amount of asymptomatic virus carriers, (2) a virus carrier with symptoms was approximately twice more likely to pass the disease to others than that of an asymptomatic virus carrier, (3) the transmission rate reduced significantly since the implementation of control measures in Mainland China, and (4) it was expected that the epidemic outbreak would be contained by early March in the selected provinces and cities in China.

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An evaluation of electrofishing as a control measure for an invasive tilapia (Oreochromis mossambicus) population in northern Australia

Marine and Freshwater Research ◽

10.1071/mf10057 ◽

2011 ◽

Vol 62 (2) ◽

pp. 110 ◽

Cited By ~ 10

Author(s):

P. A. Thuesen ◽

D. J. Russell ◽

F. E. Thomson ◽

M. G. Pearce ◽

T. D. Vallance ◽

...

Keyword(s):

Control Measure ◽

Oreochromis Mossambicus ◽

Control Measures ◽

Invasive Fish ◽

Catch Per Unit Effort ◽

Eastern Australia ◽

Stock Recruitment ◽

High Conservation ◽

Mature Fish ◽

And Control

Combating the spread of invasive fish is problematic, with eradication rarely possible and control options varying enormously in their effectiveness. In two small impoundments in north-eastern Australia, an electrofishing removal program was conducted to control an invasive tilapia population. We hypothesised that electrofishing would reduce the population density of Oreochromis mossambicus (Mozambique tilapia), to limit the risk of downstream spread into areas of high conservation value. We sampled by electrofishing monthly for 33 months. Over this period, there was an 87% decline in catch per unit effort (CPUE) of mature fish, coupled with a corresponding increase of 366% in the number of juveniles, suggesting a density-dependent response in the stock–recruitment relationship for the population. Temperature was inversely related to CPUE (r = 0.43, lag = 10 days), implying greater electrofishing efficiency in cooler months. The reduction in breeding stock is likely to reduce the risk of spread and render the population vulnerable to other control measures such as netting and/or biological control. Importantly, the current study suggests routine electrofishing may be a useful control tool for invasive fish in small impoundments when the use of more destructive techniques, such as piscicides, is untenable.

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Incidence of dengue fever and risk of its transmission to the Afghan travelers to tropical regions: A discussion paper

Journal of Inventions in Biomedical and Pharmaceutical Sciences ◽

10.26452/jibps.v5i3.1438 ◽

2020 ◽

Vol 5 (3) ◽

pp. 27-30

Author(s):

Tafseera Hashemi

Keyword(s):

Dengue Fever ◽

Control Measure ◽

Control Measures ◽

Discussion Paper ◽

Media Campaigns ◽

Tropical Regions ◽

Asian Tiger ◽

Tropical Areas ◽

And Migration ◽

And Control

This review article discusses the transmission or importation of dengue fever to Afghanistan by travelers from tropical countries. The dengue fever, transmit by aedes mosquito (Asian tiger) to humans. The Asian tiger is found in tropical parts of world especially in east parts of Asia like Malaysia, India and Pakistan. The disease spreads or transmit through a bite by mosquito and from infected person to mosquito and thus to others. Millions of Afghans are travelling around the globe each year, especially to Pakistan, India and Iran, where the dengue virus found. Living in tropical areas, climate changes, global warming and urbanizations leads to the transmission and migration of the disease from one person to another. The aim of this paper was to know the mood of transmission, existence of dengue fever in Afghanistan and its control measures. Therefore, travelers must be advised, prior to travelling to dengue prone areas. Mass media campaigns, awareness workshops and control measure must be adapted by the Ministry of Public Health about dengue fever.

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