Quantifying the relative effects of environmental and direct transmission of norovirus

Norovirus is a common cause of outbreaks of acute gastroenteritis in health- and child-care settings, with serial outbreaks also frequently observed aboard cruise ships. The relative contributions of environmental and direct person-to-person transmission of norovirus have hitherto not been quantified. We employ a novel mathematical model of norovirus transmission, and fit the model to daily incidence data from a major norovirus outbreak on a cruise ship, and examine the relative efficacy of potential control strategies aimed at reducing environmental and/or direct transmission. The reproduction number for environmental and direct transmission combined is R 0 tot = 7.2 [6.1,9.5], and of environmental transmission alone is R 0 environ = 1.6 [0.9,2.6]. Direct transmission is overwhelmingly due to passenger-to-passenger contacts, but crew can act as a reservoir of infection from cruise to cruise. This is the first quantification of the relative roles of environmental and direct transmission of norovirus. While environmental transmission has the potential to maintain a sustained series of outbreaks aboard a cruise ship in the absence of strict sanitation practices, direct transmission dominates. We find that intensive promotion of good hand washing practices may prevent outbreaks. Isolation of ill passengers and cleaning are beneficial, but appear to be less efficacious at outbreak control.

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Global convergence of COVID-19 basic reproduction number and estimation from early-time SIR dynamics

10.1101/2020.04.10.20060954 ◽

2020 ◽

Cited By ~ 3

Author(s):

Gabriel G. Katul ◽

Assaad Mrad ◽

Sara Bonetti ◽

Gabriele Manoli ◽

Anthony J. Parolari

Keyword(s):

Global Convergence ◽

Basic Reproduction Number ◽

Reproduction Number ◽

Control Strategies ◽

Early Period ◽

Early Time ◽

World Health ◽

Potential Control ◽

The Usa ◽

Early Phases

AbstractThe SIR (‘susceptible-infectious-recovered’) formulation is used to uncover the generic spread mechanisms observed by COVID-19 dynamics globally, especially in the early phases of infectious spread. During this early period, potential controls were not effectively put in place or enforced in many countries. Hence, the early phases of COVID-19 spread in countries where controls were weak offer a unique perspective on the ensemble-behavior of COVID-19 basic reproduction number Ro. The work here shows that there is global convergence (i.e. across many nations) to an uncontrolled Ro = 4.5 that describes the early time spread of COVID-19. This value is in agreement with independent estimates from other sources reviewed here and adds to the growing consensus that the early estimate of Ro = 2.2 adopted by the World Health Organization is low. A reconciliation between power-law and exponential growth predictions is also featured within the confines of the SIR formulation. Implications for evaluating potential control strategies from this uncontrolled Ro are briefly discussed in the context of the maximum possible infected fraction of the population (needed for assessing health care capacity) and mortality (especially in the USA given diverging projections). Model results indicate that if intervention measures still result in Ro> 2.7 within 49 days after first infection, intervention is unlikely to be effective in general for COVID-19. Current optimistic projections place mortality figures in the USA in the range of 100,000 fatalities. For fatalities to be confined to 100,000 requires a reduction in Ro from 4.5 to 2.7 within 17 days of first infection assuming a mortality rate of 3.4%.

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Analysis of the COVID-19 Pandemic Spreading in India by an Epidemiological Model and Fractional Differential Operator

10.20944/preprints202005.0266.v1 ◽

2020 ◽

Cited By ~ 3

Author(s):

Amjad S. Shaikh ◽

Vikas S. Jadhav ◽

Munir G. Timol ◽

Kottakkaran S. Nisar ◽

I. Khan

Keyword(s):

Differential Operator ◽

Reproduction Number ◽

Control Strategies ◽

Approximate Solutions ◽

Transform Method ◽

Potential Control ◽

Fractional Differential Operator ◽

Fractional Differential ◽

Sensitive Parameters ◽

Future Outbreak

Fractional differential mathematical model unfolding the dynamics of the COVID-19 pandemic in India is presented and explored in this paper. The purpose of this study is to estimate the future outbreak of disease and potential control strategies using mathematical models in India as a whole country as well as in some of the states of the country. This model is calibrated based on reported cases of infections over the month of April 2020 in India. We have used iterative fractional complex transform method to find approximate solutions of the model having modified Riemann Liouville fractional differential operator. We have also carried out a comparative analysis between actual and estimated cumulative cases graphically, moreover, most sensitive parameters for basic reproduction number$(R_0)$ are computed and their effect on transmission dynamics of COVID-19 pandemic is investigated in detail.

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COVID-19 outbreak on the Diamond Princess cruise ship: estimating the epidemic potential and effectiveness of public health countermeasures

Journal of Travel Medicine ◽

10.1093/jtm/taaa030 ◽

2020 ◽

Vol 27 (3) ◽

Cited By ~ 149

Author(s):

J Rocklöv ◽

H Sjödin ◽

A Wilder-Smith

Keyword(s):

Public Health ◽

Initial Period ◽

Reproduction Rate ◽

Cruise Ship ◽

Incidence Data ◽

Health Measures ◽

Basic Reproduction Rate ◽

Cruise Ships ◽

Time Period ◽

The Impact

Abstract Background Cruise ships carry a large number of people in confined spaces with relative homogeneous mixing. On 3 February, 2020, an outbreak of COVID-19 on cruise ship Diamond Princess was reported with 10 initial cases, following an index case on board around 21-25th January. By 4th February, public health measures such as removal and isolation of ill passengers and quarantine of non-ill passengers were implemented. By 20th February, 619 of 3700 passengers and crew (17%) were tested positive. Methods We estimated the basic reproduction number from the initial period of the outbreak using SEIR models. We calibrated the models with transient functions of countermeasures to incidence data. We additionally estimated a counterfactual scenario in absence of countermeasures, and established a model stratified by crew and guests to study the impact of differential contact rates among the groups. We also compared scenarios of an earlier versus later evacuation of the ship. Results The basic reproduction rate was initially 4 times higher on-board compared to the ${R}_0$ in the epicentre in Wuhan, but the countermeasures lowered it substantially. Based on the modeled initial ${R}_0$ of 14.8, we estimated that without any interventions within the time period of 21 January to 19 February, 2920 out of the 3700 (79%) would have been infected. Isolation and quarantine therefore prevented 2307 cases, and lowered the ${R}_0$ to 1.78. We showed that an early evacuation of all passengers on 3 February would have been associated with 76 infected persons in their incubation time. Conclusions The cruise ship conditions clearly amplified an already highly transmissible disease. The public health measures prevented more than 2000 additional cases compared to no interventions. However, evacuating all passengers and crew early on in the outbreak would have prevented many more passengers and crew from infection.

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An Adaptive, Interacting, Cluster-Based Model Accurately Predicts the Transmission Dynamics of COVID-19

10.1101/2020.04.21.20074211 ◽

2020 ◽

Cited By ~ 1

Author(s):

R. Ravinder ◽

Sourabh Singh ◽

Suresh Bishnoi ◽

Amreen Jan ◽

Abhinav Sinha ◽

...

Keyword(s):

Temporal Variation ◽

United States Of America ◽

Reproduction Number ◽

Control Strategies ◽

Management Strategies ◽

The United States ◽

Mitigation Measures ◽

Spatial And Temporal Variation ◽

Incidence Data ◽

Efficient Resource

AbstractThe SARS-CoV-2 driven disease, COVID-19, is presently a pandemic with increasing human and monetary costs. COVID-19 has put an unexpected and inordinate degree of pressure on healthcare systems of strong and fragile countries alike. In order to launch both containment and mitigation measures, each country requires accurate estimates of COVID-19 incidence as such preparedness allows agencies to plan efficient resource allocation and design control strategies. Here, we have developed a new adaptive, interacting, and cluster-based mathematical model to predict the granular trajectory COVID-19. We have analyzed incidence data from three currently afflicted countries of Italy, the United States of America, and India, and show that our approach predicts state-wise COVID-19 spread for each country with high accuracy. We show that R0 as the basic reproduction number exhibits significant spatial and temporal variation in these countries. However, by including a new function for temporal variation of R0 in an adaptive fashion, the predictive model provides highly reliable estimates of asymptomatic and undetected COVID-19 patients, both of which are key players in COVID-19 transmission. Our dynamic modeling approach can be applied widely and will provide a new fillip to infectious disease management strategies worldwide.

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Transmission dynamics of the COVID-19 epidemic in India and modelling optimal lockdown exit strategies

10.1101/2020.05.13.20096826 ◽

2020 ◽

Cited By ~ 7

Author(s):

Mohak Gupta ◽

Saptarshi Soham Mohanta ◽

Aditi Rao ◽

Giridara Gopal Parameswaran ◽

Mudit Agarwal ◽

...

Keyword(s):

Symptom Onset ◽

Reproduction Number ◽

Control Strategies ◽

Tertiary Care ◽

Time Lag ◽

Control Measures ◽

Surveillance Systems ◽

Care Hospital ◽

Incidence Data ◽

Second Wave

Background: The coronavirus disease 2019 (COVID-19) has caused over 3 200 000 cases and 230 000 deaths as on 2 May 2020, and has quickly become an unprecedented global health threat. India, with its unique challenges in fighting this pandemic, imposed one of the worlds strictest and largest population-wide lockdown on 25 March 2020. Here, we estimated key epidemiological parameters and evaluated the effect of control measures on the COVID-19 epidemic in India. Through a modelling approach, we explored various strategies to exit the lockdown. Methods: We obtained data from 140 confirmed COVID-19 patients at a tertiary care hospital in India to estimate the delay from symptom onset to confirmation and the proportion of cases without symptoms. We estimated the basic reproduction number (R0) and time-varying effective reproduction number (Rt) after adjusting for imported cases and reporting lag, using incidence data from 4 March to 25 April 2020 for India. We built upon the SEIR model to account for underreporting, reporting delays, and varying asymptomatic proportion and infectivity. Using this model, we simulated lockdown relaxation under various scenarios to evaluate its effect on the second wave, and also modelled increased detection through testing. We hypothesised that increased testing after lockdown relaxation will decrease the epidemic growth enough to allow for a greater resumption of normal social mixing thus minimising the social and economic fallout. Findings: The median delay from symptom onset to confirmation (reporting lag) was estimated to be 2·68 days (95% CI 2·00−3·00) with an IQR of 2·03 days (95% CI 1·00−3·00). 60·7% of confirmed COVID-19 cases (n=140) were found to be asymptomatic. The R0 for India was estimated to be 2·083 (95% CI 2·044−2·122 ; R2 = 0·972), while the Rt gradually down trended from 1·665 (95%CI 1·539−1·789) on 30 March to 1·159 (95% CI 1·128−1·189) on 22 April. In the modelling, we observed that the time lag from date of lockdown relaxation to start of second wave increases as lockdown is extended farther after the first wave peak. This benefit was greater for a gradual relaxation as compared to a sudden lifting of lockdown. We found that increased detection through testing decreases the number of total infections and symptomatic cases, and the benefit of detecting each extra case was higher when prevailing transmission rates were higher (as when restrictions are relaxed). Lower levels of social restrictions when coupled with increased testing, could achieve similar outcomes as an aggressive social distancing regime where testing was not increased. Interpretation: The aggressive control measures in India since 25 March have produced measurable reductions in transmission, although suppression needs to be maintained to achieve sub-threshold Rt. Additional benefits for mitigating the second wave can be achieved if lockdown can be feasibly extended farther after the peak of active cases has passed. Aggressive measures like lockdowns may inherently be enough to suppress the epidemic, however other measures need to be scaled up as lockdowns are relaxed. Expanded testing is expected to play a pivotal role in the lockdown exit strategy and will determine the degree of return to normalcy that will be possible. Increased testing coverage will also ensure rapid feedback from surveillance systems regarding any resurgence in cases, so that geo-temporally targeted measures can be instituted at the earliest. Considering that asymptomatics play an undeniable role in transmission of COVID-19, it may be prudent to reduce the dependence on presence of symptoms for implementing control strategies, behavioral changes and testing.

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Eco-Environmental Aspects of COVID-19 Pandemic and Potential Control Strategies

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18073488 ◽

2021 ◽

Vol 18 (7) ◽

pp. 3488

Author(s):

Rashid Nazir ◽

Jawad Ali ◽

Ijaz Rasul ◽

Emilie Widemann ◽

Sarfraz Shafiq

Keyword(s):

Control Strategies ◽

Public Awareness ◽

Noise Pollution ◽

Environmental Aspects ◽

Potential Control ◽

Health Infrastructure ◽

The People ◽

Slum Dwellers ◽

Hospital Wastes ◽

Future Outbreak

A new coronavirus-strain from a zoonotic reservoir (probably bat)—termed as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)—has recently claimed more than two million deaths worldwide. Consequently, a burst of scientific reports on epidemiology, symptoms, and diagnosis came out. However, a comprehensive understanding of eco-environmental aspects that may contribute to coronavirus disease 2019 (COVID-19) spread is still missing, and we therefore aim to focus here on these aspects. In addition to human–human direct SARS-CoV-2 transmission, eco-environmental sources, such as air aerosols, different public use objects, hospital wastes, livestock/pet animals, municipal wastes, ventilation facilities, soil and groundwater potentially contribute to SARS-CoV-2 transmission. Further, high temperature and humidity were found to limit the spread of COVID-19. Although the COVID-19 pandemic led to decrease air and noise pollution during the period of lockdown, increased use of masks and gloves is threatening the environment by water and soil pollutions. COVID-19 badly impacted all the socio-economic groups in different capacities, where women, slum dwellers, and the people lacking social protections are the most vulnerable. Finally, sustainable strategies, waste management, biodiversity reclaim, eco-friendly lifestyle, improved health infrastructure and public awareness, were proposed to minimize the COVID-19 impact on our society and environment. These strategies will seemingly be equally effective against any future outbreak.

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Evaluation of an Hygienic Intervention in Child Day-Care Centers

PEDIATRICS ◽

10.1542/peds.94.6.991 ◽

1994 ◽

Vol 94 (6) ◽

pp. 991-994

Author(s):

Jonathan B. Kotch ◽

Ann H. Faircloth ◽

Kristen A. Weigle ◽

David J. Weber ◽

Richard M. Clifford ◽

...

Keyword(s):

Day Care ◽

Significant Rise ◽

Hand Washing ◽

Day Care Centers ◽

Incidence Data ◽

Child Day Care ◽

Care Givers ◽

Child Day Care Centers ◽

The Cost ◽

The Impact

The growing use of child day-care centers (CDCCs) has produced a significant rise in morbidity due to infectious diseases which carry such consequences as discomfort, disability, and parental anxiety.1,2 Haskins conservatively estimated the cost of day-care illnesses among children to be $1.8 billion.3 To this must be added the cost of parents' and care givers' excess illness attributable to CDCCs. No published study describes a successful intervention to reduce the risk of upper respiratory disease in CDCCs. Although many research groups have advocated hand washing and diapering hygiene as a means of reducing the spread of enteric disease in CDCCs,4-11 there are only two controlled studies in the literature. In their pioneering work, Black et al showed the incidence of diarrhea in CDCCs following a rigorously monitored hand-washing program to be nearly twice that in intervention centers.12 Bartlett et al monitored the impact of hand washing in randomly assigned CDCCs and found no intervention effect. However, rates of diarrhea were significantly lower among children in the actively monitored centers regardless of intervention status.13 These studies share several limitations: the sources of incidence data were not blinded to center intervention status, the analyses did not statistically control for potential confounders, and non-independence of multiple diarrhea episodes in the same child were not accounted for. The purposes of our study were to develop a feasible, multicomponent hygienic intervention and to carefully measure its impact while controlling for sources of bias. Use of trade names is for identification only and does not constitute endorsement by the Public Health Service, the Centers for Disease Control and Prevention, or any of the other co-sponsors of this conference.

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Farmer attitudes to injurious pecking in laying hens and to potential control strategies

Animal Welfare ◽

10.7120/09627286.25.1.029 ◽

2016 ◽

Vol 25 (1) ◽

pp. 29-38 ◽

Cited By ~ 10

Author(s):

LJ Palczynski ◽

H Buller ◽

SL Lambton ◽

CA Weeks

Keyword(s):

Laying Hens ◽

Control Strategies ◽

Farmer Attitudes ◽

Potential Control

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Transmission potential of COVID-19 in South Korea

10.1101/2020.02.27.20028829 ◽

2020 ◽

Cited By ~ 23

Author(s):

Eunha Shim ◽

Amna Tariq ◽

Wongyeong Choi ◽

Yiseul Lee ◽

Gerardo Chowell

Keyword(s):

South Korea ◽

Reproduction Number ◽

Social Distancing ◽

Transmission Potential ◽

Incidence Data ◽

Novel Coronavirus

AbstractSince the first identified individual of 2019 novel coronavirus (COVID-19) infection on Jan 20, 2020 in South Korea, the number of confirmed cases rapidly increased. As of Feb 26, 2020, 1,261 cases of COVID-19 including 12 deaths were confirmed in South Korea. Using the incidence data of COVID-19, we estimate the reproduction number at 1.5 (95% CI: 1.4-1.6), which indicates sustained transmission and support the implementation of social distancing measures to rapidly control the outbreak.

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Optimal Control of a Dengue-Dengvaxia Model: Comparison Between Vaccination and Vector Control

Computational and Mathematical Biophysics ◽

10.1515/cmb-2020-0124 ◽

2021 ◽

Vol 9 (1) ◽

pp. 198-212

Author(s):

Cheryl Q. Mentuda

Keyword(s):

Optimal Control ◽

Vector Control ◽

Basic Reproduction Number ◽

Human Population ◽

Model Comparison ◽

Reproduction Number ◽

Control Strategies ◽

Minimum Principle ◽

Transmitted Disease ◽

The Basic Reproduction Number

Abstract Dengue is the most common mosquito-borne viral infection transmitted disease. It is due to the four types of viruses (DENV-1, DENV-2, DENV-3, DENV-4), which transmit through the bite of infected Aedes aegypti and Aedes albopictus female mosquitoes during the daytime. The first globally commercialized vaccine is Dengvaxia, also known as the CYD-TDV vaccine, manufactured by Sanofi Pasteur. This paper presents a Ross-type epidemic model to describe the vaccine interaction between humans and mosquitoes using an entomological mosquito growth population and constant human population. After establishing the basic reproduction number ℛ0, we present three control strategies: vaccination, vector control, and the combination of vaccination and vector control. We use Pontryagin’s minimum principle to characterize optimal control and apply numerical simulations to determine which strategies best suit each compartment. Results show that vector control requires shorter time applications in minimizing mosquito populations. Whereas vaccinating the primary susceptible human population requires a shorter time compared to the secondary susceptible human.

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