scholarly journals Synergetic measures needed to control infection waves and contain SARS-CoV-2 transmission

2021 ◽  
Author(s):  
Hang Su ◽  
Yafang Cheng ◽  
Ulrich Poeschl
Keyword(s):  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Scientific Discourse ◽  
Protective Measure ◽  
Protective Measures ◽  
Vaccination Rates ◽  
The Public ◽  
Individual Measure ◽  
The Impact ◽  
Pharmaceutical Interventions

The public and scientific discourse on how to mitigate the COVID-19 pandemic is often focused on the impact of individual protective measures, in particular on immunization by vaccination. In view of changing virus variants and conditions, however, it seems not clear if vaccination or any other single protective measure alone may suffice to contain the transmission of SARS-CoV-2. Here, we investigate the effectiveness and synergies of vaccination and different non-pharmaceutical interventions such as universal masking (surgical, N95/FFP2), distancing & ventilation, contact reduction, and testing & isolation as a function of compliance in the population. We find that it would be difficult to contain SARS-CoV-2 transmission by any individual measure as currently available under realistic conditions. Instead, we show how multiple synergetic measures can be and have to be combined to decrease and keep the effective reproduction number (Re) below unity, even for virus variants with increased basic reproduction number (R0). We suggest that the presented approach and results can be used to design and communicate efficient strategies for mitigating the COVID-19 pandemic, depending on R0 as well as the efficacy and compliance achieved with each protective measure. At vaccination rates around 70%, the combination and synergies of universal masking, distancing & ventilation, and testing & isolation with moderate compliances around 30% appear well suited to keep Re below 1 and prevent or suppress infection waves. Higher compliance or additional measures like contact reductions (confinement/lockdown) are required to effectively and swiftly break intense waves of infection. For schools, we find that the transmission of SARS-CoV-2 can be contained by 2-3 tests per week combined with distancing & ventilation and masking.

scholarly journals A deterministic, age-stratified, extended SEIRD model for assessing the effect of non-pharmaceutical interventions on SARS-CoV-2 spread in Belgium

2020 ◽  
Author(s):  
Tijs W. Alleman ◽  
Jenna Vergeynst ◽  
Elena Torfs ◽  
Daniel Illana Gonzalez ◽  
Ingmar Nopens ◽  
...  
Keyword(s):  
Public Health ◽  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Social Contact ◽  
The Elderly ◽  
Public Health Care ◽  
Successful Implementation ◽  
The Public ◽  
Pharmaceutical Interventions ◽  
The Basic Reproduction Number

As a response to the rapidly rising number of SARS-CoV-2 infections, the Belgian governments imposed strict social contact restrictions on March 13th, 2020. After nearly two months, the curve was successfully flattened and social restrictions were gradually relaxed. Unfortunately, pharmaceutical interventions are not yet available so it is expected that preventing COVID-19 outbreaks will depend mostly on the successful implementation of non-pharmaceutical interventions, hence the need for well-informed models. In this study, we built a deterministic, continuous-time, age-stratified-SEIRD model with detailed hospital dynamics. Because the hospitalization data for Belgium are not made publically available by the Belgian Scientific Institute of Public Health (Sciensano), we computed the hospitalization parameters based on data from 370 patients treated in two Ghent (Belgium) hospitals. The basic reproduction number was estimated as R0 = 2.83 in March 2020 and the model fits the hospitalization and ICU admission incidence under lockdown measures well. Despite the relaxation of social restrictions, hospitalizations have been steadily declining. We recomputed the basic reproduction number under lockdown release and found that it had to be as low as R0 = 0.73 to explain the endemic trend. We further found that although the basic reproduction number in the population older than 70 years was smaller than one, this group compromises nearly half of the expected hospitalizations. This indicates that the protection of the elderly may be the most efficient way to reduce strain on the public health care system in case of another SARS-CoV-2 outbreak.

scholarly journals Rapid Impact Analysis of B 1.1.7 Variant on the Spread of SARS-CoV-2 in North Carolina

2021 ◽  
Author(s):  
Michael DeWitt
Keyword(s):  
North Carolina ◽  
Impact Analysis ◽  
Reproduction Number ◽  
Population Level ◽  
Vaccination Rate ◽  
Vaccination Rates ◽  
Current Vaccine ◽  
Spread Of Infection ◽  
The Impact ◽  
Pharmaceutical Interventions

AbstractBackgroundSeveral cases of the B1.1.7 variant of the SARS-CoV-2 virus were identified in North Carolina first on January 23, 2021 in Mecklenburg County and later in Guilford County on January 28, 2021.[1,2] This variant has been associated with higher levels of transmissibility.[3–6] This study examines the potential impact of increased transmissibility as the B1.1.7 variant becomes more predominant given current vaccine distribution plans and existing non-pharmaceutical interventions (NPIs).MethodWe explored the anticipated impact on the effective reproduction number for North Carolina and Guilford County given the date of import of B1.1.7. The approximate growth rate in proportion of B1.1.7 observed in the United Kingdom was fit and used to establish the estimate share of B1.1.7 circulating in North Carolina. Using the nowcasted reproduction numbers, a stochastic discrete compartmental model was fit with the current vaccination rates and B1.1.7 transmissibility to estimate the impact on the effective reproduction number.ResultsWe found that the effective reproduction number for North Carolina and Guilford County may exceed one, indicating a return to accelerating spread of infection in April as the proportion of B1.1.7 increases. The effective reproduction number will likely decrease into March, then increase as the proportion of B1.1.7 increases in circulation in the population.ConclusionsExisting non-pharmaceutical interventions will need to remain in effect through the spring. Given the current vaccination rate and these interventions, it is likely that there will be an increase in SARS-CoV-2 infections. The impact of the variant will likely be heterogeneous across North Carolina given the reproduction number and volume of susceptible persons in each county at the time of introduction of the variant. Age-based vaccinations will likely reduce the overall impact on hospitalizations. This analysis underlines the need for population level genetic surveillance to confirm the proportion of variants circulating.

scholarly journals Accounting for underreporting in mathematical modelling of transmission and control of COVID-19 in Iran

2020 ◽  
Author(s):  
Meead Saberi ◽  
Homayoun Hamedmoghadam ◽  
Kaveh Madani ◽  
Helen M. Dolk ◽  
Andrei S. Morgan ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Estimation Method ◽  
Case Fatality ◽  
Transmission Model ◽  
School Closures ◽  
The Public ◽  
Case Fatality Ratio ◽  
And Control ◽  
The Impact ◽  
Pharmaceutical Interventions

SUMMARYBackgroundIran has been the hardest hit country by the outbreak of SARS-CoV-2 in the Middle East with 74,877 confirmed cases and 4,683 deaths as of 15 April 2020. With a relatively high case fatality ratio and limited testing capacity, the number of confirmed cases reported is suspected to suffer from significant under-reporting. Therefore, understanding the transmission dynamics of COVID-19 and assessing the effectiveness of the interventions that have taken place in Iran while accounting for the uncertain level of underreporting is of critical importance. We use a mathematical epidemic model utilizing official confirmed data and estimates of underreporting to understand how transmission in Iran has been changing between February and April 2020.MethodsWe developed a compartmental transmission model to estimate the effective reproduction number and its fluctuations since the beginning of the outbreak in Iran. We associate the variations in the effective reproduction number with a timeline of interventions and national events. The estimation method also accounts for the underreporting due to low case ascertainment by estimating the percentage of symptomatic cases using delay-adjusted case fatality ratio based on the distribution of the delay from hospitalization-to-death.FindingsOur estimates of the effective reproduction number ranged from 0.66 to 1.73 between February and April 2020, with a median of 1.16. We estimate a reduction in the effective reproduction number during this period, from 1.73 (95% CI 1.60 – 1.87) on 1 March 2020 to 0.69 (95% CI 0.68-0.70) on 15 April 2020, due to various non-pharmaceutical interventions including school closures, a ban on public gatherings including sports and religious events, and full or partial closure of non-essential businesses. Based on these estimates and given that a near complete containment is no longer feasible, it is likely that the outbreak may continue until the end of the 2020 if the current level of physical distancing and interventions continue and no effective vaccination or therapeutic are developed and made widely available.InterpretationThe series of non-pharmaceutical interventions and the public compliance that took place in Iran are found to be effective in slowing down the speed of the spread of COVID-19 within the studied time period. However, we argue that if the impact of underreporting is overlooked, the estimated transmission and control dynamics could mislead the public health decisions, policy makers, and general public especially in the earlier stages of the outbreak.FundingNil.

scholarly journals The effects of non-pharmaceutical interventions on SARS-CoV-2 transmission in different socioeconomic populations in Kuwait: a modeling study

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Fatima Khadadah ◽  
Abdullah A. Al-Shammari ◽  
Ahmad Alhashemi ◽  
Dari Alhuwail ◽  
Bader Al-Saif ◽  
...  
Keyword(s):  
Disease Transmission ◽  
Reproduction Number ◽  
Transmission Model ◽  
Socioeconomic Groups ◽  
Before And After ◽  
Cross Transmission ◽  
Community Transmission ◽  
The Impact ◽  
Pharmaceutical Interventions ◽  
The Basic Reproduction Number

Abstract Background Aggressive non-pharmaceutical interventions (NPIs) may reduce transmission of SARS-CoV-2. The extent to which these interventions are successful in stopping the spread have not been characterized in countries with distinct socioeconomic groups. We compared the effects of a partial lockdown on disease transmission among Kuwaitis (P1) and non-Kuwaitis (P2) living in Kuwait. Methods We fit a modified metapopulation SEIR transmission model to reported cases stratified by two groups to estimate the impact of a partial lockdown on the effective reproduction number ($$ {\mathcal{R}}_e $$ R e ). We estimated the basic reproduction number ($$ {\mathcal{R}}_0 $$ R 0 ) for the transmission in each group and simulated the potential trajectories of an outbreak from the first recorded case of community transmission until 12 days after the partial lockdown. We estimated $$ {\mathcal{R}}_e $$ R e values of both groups before and after the partial curfew, simulated the effect of these values on the epidemic curves and explored a range of cross-transmission scenarios. Results We estimate $$ {\mathcal{R}}_e $$ R e at 1·08 (95% CI: 1·00–1·26) for P1 and 2·36 (2·03–2·71) for P2. On March 22nd, $$ {\mathcal{R}}_e $$ R e for P1 and P2 are estimated at 1·19 (1·04–1·34) and 1·75 (1·26–2·11) respectively. After the partial curfew had taken effect, $$ {\mathcal{R}}_e $$ R e for P1 dropped modestly to 1·05 (0·82–1·26) but almost doubled for P2 to 2·89 (2·30–3·70). Our simulated epidemic trajectories show that the partial curfew measure greatly reduced and delayed the height of the peak in P1, yet significantly elevated and hastened the peak in P2. Modest cross-transmission between P1 and P2 greatly elevated the height of the peak in P1 and brought it forward in time closer to the peak of P2. Conclusion Our results indicate and quantify how the same lockdown intervention can accentuate disease transmission in some subpopulations while potentially controlling it in others. Any such control may further become compromised in the presence of cross-transmission between subpopulations. Future interventions and policies need to be sensitive to socioeconomic and health disparities.

scholarly journals Threshold Dynamics of a Huanglongbing Model with Logistic Growth in Periodic Environments

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jianping Wang ◽  
Shujing Gao ◽  
Yueli Luo ◽  
Dehui Xie
Keyword(s):  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Logistic Growth ◽  
Threshold Dynamics ◽  
Global Dynamics ◽  
Globally Asymptotically Stable ◽  
Linear Integral ◽  
The Impact ◽  
Disease Free ◽  
The Basic Reproduction Number

We analyze the impact of seasonal activity of psyllid on the dynamics of Huanglongbing (HLB) infection. A new model about HLB transmission with Logistic growth in psyllid insect vectors and periodic coefficients has been investigated. It is shown that the global dynamics are determined by the basic reproduction numberR0which is defined through the spectral radius of a linear integral operator. IfR0< 1, then the disease-free periodic solution is globally asymptotically stable and ifR0> 1, then the disease persists. Numerical values of parameters of the model are evaluated taken from the literatures. Furthermore, numerical simulations support our analytical conclusions and the sensitive analysis on the basic reproduction number to the changes of average and amplitude values of the recruitment function of citrus are shown. Finally, some useful comments on controlling the transmission of HLB are given.

scholarly journals A retrospective study of a pre-travel consultation in the Lisbon Metropolitan Area, Portugal

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
D Galhano Lopes ◽  
M Bragança Pereira ◽  
M Machado Gil ◽  
S Duarte ◽  
A Moreira ◽  
...  
Keyword(s):  
Individual Characteristics ◽  
Yellow Fever Vaccine ◽  
Medical Community ◽  
Therapeutic Drug ◽  
Protective Measures ◽  
The Public ◽  
Related Risk ◽  
Medical Referral ◽  
The Impact

Abstract Background Travel from Portugal to other countries has increased in the past 5 years. A pre-travel health consultation is advised to all travellers to raise awareness and reduce travel-related risk. We describe the experience of a pre-travel consultation centre in the public health service. Methods A retrospective observational study about consultations in an international vaccination centre between 2014-2018. Variables included were: sex, age, destination, purpose, referral, and prescriptions. Descriptive analyses were performed for all variables. Results Between 2014 and 2018, there were 1,546 consultations. Regarding individual characteristics, 54% were female, and 80% had between 15 and 64 years of age. There was no referral in 66% of the consultations, followed by 16% from general practitioners in the Primary Care Centres Group. The leading destination was Africa (54%), in a downward trend (74% in 2015 and 32% in 2018) followed by Asia (18%) with an upward trend (12% to 28% in the same period). The primary purpose was tourism (83%), followed by work (9%). In total, 3,287 vaccines were prescribed with typhoid fever vaccine accounting for 26%, hepatitis A vaccine 22%, and yellow fever vaccine 15%. Mefloquine was the primary therapeutic drug prescribed for destinations with risk for malaria (41%). Regarding destinations with low risk for malaria, in 42% of the consultations, personal protective measures were the only recommendation. Conclusions Our data show that pre-travel consultations seem to be valued and actively asked for by travellers, but medical referral is still insufficient. Regarding health promotion and prevention of diseases, tracking trends in the most common destinations allows to optimize the information provided in the consultation, effectively capacitating the traveller to recognize and act on the most common travel-related health risks. In further studies, a post-travel follow-up should be carried out to determine the impact of the consultation. Key messages Pre-travel consultation is an actively sought-after service by the community, but awareness should be promoted in the medical community. Pre-travel consultation can have an important role in the health literacy of travellers.

A THEORETICAL ASSESSMENT OF THE EFFECTS OF DISTRIBUTED DELAY ON THE TRANSMISSION DYNAMICS OF HEPATITIS B

2015 ◽  
Vol 23 (03) ◽  
pp. 423-455
Author(s):  
P. MOUOFO TCHINDA ◽  
JEAN JULES TEWA ◽  
BOULECHARD MEWOLI ◽  
SAMUEL BOWONG
Keyword(s):  
Drug Therapy ◽  
Hepatitis B ◽  
Basic Reproduction Number ◽  
Disease Transmission ◽  
Time Delays ◽  
Reproduction Number ◽  
Distributed Delay ◽  
Global Dynamics ◽  
The Impact ◽  
The Basic Reproduction Number

In this paper, we investigate the global dynamics of a system of delay differential equations which describes the interaction of hepatitis B virus (HBV) with both liver and blood cells. The model has two distributed time delays describing the time needed for infection of cell and virus replication. We also include the efficiency of drug therapy in inhibiting viral production and the efficiency of drug therapy in blocking new infection. We compute the basic reproduction number and find that increasing delays will decrease the value of the basic reproduction number. We study the sensitivity analysis on the key parameters that drive the disease dynamics in order to determine their relative importance to disease transmission and prevalence. Our analysis reveals that the model exhibits the phenomenon of backward bifurcation (where a stable disease-free equilibrium (DFE) co-exists with a stable endemic equilibrium when the basic reproduction number is less than unity). Numerical simulations are presented to evaluate the impact of time-delays on the prevalence of the disease.

scholarly journals The effect of heterogeneous infectious period and contagiousness on the dynamics ofSalmonellatransmission in dairy cattle

2008 ◽  
Vol 136 (11) ◽  
pp. 1496-1510 ◽  
Author(s):  
C. LANZAS ◽  
S. BRIEN ◽  
R. IVANEK ◽  
Y. LO ◽  
P. P. CHAPAGAIN ◽  
...  
Keyword(s):  
Dairy Cattle ◽  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Transmission Dynamics ◽  
Infectious Period ◽  
Specific Group ◽  
Infection Transmission ◽  
Force Of Infection ◽  
The Impact

SUMMARYThe objective of this study was to address the impact of heterogeneity of infectious period and contagiousness onSalmonellatransmission dynamics in dairy cattle populations. We developed three deterministic SIR-type models with two basic infected stages (clinically and subclinically infected). In addition, model 2 included long-term shedders, which were defined as individuals with low contagiousness but long infectious period, and model 3 included super-shedders (individuals with high contagiousness and long infectious period). The simulated dynamics, basic reproduction number (R0) and critical vaccination threshold were studied. Clinically infected individuals were the main force of infection transmission for models 1 and 2. Long-term shedders had a small impact on the transmission of the infection and on the estimated vaccination thresholds. The presence of super-shedders increasesR0and decreases the effectiveness of population-wise strategies to reduce infection, making necessary the application of strategies that target this specific group.

scholarly journals Seasonality Impact on the Transmission Dynamics of Tuberculosis

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Yali Yang ◽  
Chenping Guo ◽  
Luju Liu ◽  
Tianhua Zhang ◽  
Weiping Liu
Keyword(s):  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Autonomous Systems ◽  
Positive Periodic Solution ◽  
Transmission Dynamics ◽  
Uniform Persistence ◽  
Globally Asymptotically Stable ◽  
The Impact ◽  
Disease Free ◽  
The Basic Reproduction Number

The statistical data of monthly pulmonary tuberculosis (TB) incidence cases from January 2004 to December 2012 show the seasonality fluctuations in Shaanxi of China. A seasonality TB epidemic model with periodic varying contact rate, reactivation rate, and disease-induced death rate is proposed to explore the impact of seasonality on the transmission dynamics of TB. Simulations show that the basic reproduction number of time-averaged autonomous systems may underestimate or overestimate infection risks in some cases, which may be up to the value of period. The basic reproduction number of the seasonality model is appropriately given, which determines the extinction and uniform persistence of TB disease. If it is less than one, then the disease-free equilibrium is globally asymptotically stable; if it is greater than one, the system at least has a positive periodic solution and the disease will persist. Moreover, numerical simulations demonstrate these theorem results.

Impact-Resistant Performance Analysis of Composite Laminates for Reinforced Concrete Beam Fixed and Hinged at Different Ends

2013 ◽  
Vol 482 ◽  
pp. 30-33
Author(s):  
Run Lin Yang ◽  
Li Zhao ◽  
Juan Hua Zhou
Keyword(s):  
Reinforced Concrete ◽  
Composite Laminates ◽  
Concrete Beam ◽  
Impact Load ◽  
Reinforced Concrete Beam ◽  
Protective Measure ◽  
Protective Effects ◽  
Structural Members ◽  
Protective Measures ◽  
The Impact

Structural members are vulnerable to be damaged under the impact loads. According to traditional design methods, the impact load is seldomly considered. However, recently this situation is changed gradually. In view of this, impact-resistant performance of a new composite protective device was analyzed. A reinforced concrete beam with composite laminates, which was fixed at one end and hinged at the other end, was studied. Totally, the four cases including the unprotected, the rigid, the flexible and the composite protective measures were considered. The protective effects of the different measures can be compared by observing the strain, the displacement, the acceleration and the impact force of the target beam. Simulation results show that the composite protective measure can improve the impact-resistant effect of the target beam significantly and its dynamic response is suppressed effectively.

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