scholarly journals Decline in global transmission rates of COVID-19

Author(s):  
Ethan Romero-Severson ◽  
Nick Hengartner ◽  
Grant Meadors ◽  
Ruian Ke

AbstractOur method uses a hybrid deterministic and stochastic formalism that allows for time variable transmission rates and detection probabilities. The model was fit using iterated particle filtering to case count and death count time series from 51 countries. We found evidence for a declining transmission rate in 42 of the 51 examined countries. Of those 42 countries 34 have significant evidence for subcritical transmission rates, although the decline in new cases are relatively slow compared to the initial growth rates. This suggests that global scale social distancing efforts to slow the spread of COVID-19 are effective although they need to be strengthened in many regions and maintained in others to avoid further resurgence of COVID-19. The slow decline also suggests alternative strategies to control the virus are needed before social distancing efforts are partially relaxed.


2021 ◽  
Author(s):  
Paul Tupper ◽  
Shraddha Pai ◽  
Caroline Colijn ◽  

The role of schools in the spread of the COVID-19 pandemic is controversial, with some claiming they are an important driver of the pandemic and others arguing that transmission in schools is negligible. School cluster reports that have been collected in various jurisdictions are a source of data about transmission in schools. These reports consist of the name of a school, a date, and the number of students known to be infected. We provide a simple model for the frequency and size of clusters in this data, based on random arrivals of index cases at schools who then infect their classmates with a highly variable rate, fitting the overdispersion evident in the data. We fit our model to reports for several jurisdictions in the US and Canada, providing estimates of mean and dispersion for cluster size, whilst factoring in imperfect ascertainment. Our parameter estimates are robust to variations in ascertainment fraction. We use these estimates in three ways: i) to explore how uneven the distribution of cases is among different clusters in different jurisdictions (that is, what fraction of cases are in the 20% largest clusters), ii) to estimate how long it will be until we see a cluster a given size in jurisdiction, and iii) to determine the distribution of instantaneous transmission rate β among different index case. We show how these latter distribution can be used in simulations of school transmission where we explore the effect of different interventions, in the context of highly variable transmission rates.



2021 ◽  
Author(s):  
Alexander Chudik ◽  
M. Hashem Pesaran ◽  
Alessandro Rebucci

AbstractThis paper estimates time-varying COVID-19 reproduction numbers worldwide solely based on the number of reported infected cases, allowing for under-reporting. Estimation is based on a moment condition that can be derived from an agent-based stochastic network model of COVID-19 transmission. The outcomes in terms of the reproduction number and the trajectory of per-capita cases through the end of 2020 are very diverse. The reproduction number depends on the transmission rate and the proportion of susceptible population, or the herd immunity effect. Changes in the transmission rate depend on changes in the behavior of the virus, re-flecting mutations and vaccinations, and changes in people’s behavior, reflecting voluntary or government mandated isolation. Over our sample period, neither mutation nor vaccination are major factors, so one can attribute variation in the transmission rate to variations in behavior. Evidence based on panel data models explaining transmission rates for nine European countries indicates that the diversity of outcomes resulted from the non-linear interaction of mandatory containment measures, voluntary precautionary isolation, and the economic incentives that gov-ernments provided to support isolation. These effects are precisely estimated and robust to various assumptions. As a result, countries with seemingly different social distancing policies achieved quite similar outcomes in terms of the reproduction number. These results imply that ignoring the voluntary component of social distancing could introduce an upward bias in the estimates of the effects of lock-downs and support policies on the transmission rates.JEL ClassificationD0, F6, C4, I120, E7



Coronaviruses ◽  
2020 ◽  
Vol 01 ◽  
Author(s):  
Rashmi Saxena Pal ◽  
Yogendra Pal ◽  
Pranay Wal ◽  
Ankita Wal ◽  
Nikita Saraswat

Background: WHO declared COVID-19 a global pandemic. New cases are being added every day, as the case count in United States are to the maximum. No drugs or biologics are yet found to be effective for the prevention or treatment of COVID-19. Objective: To discuss the possibilities of available treatments available. Materials & Methods: Brief out-look is undertaken over the past issues available over the similar situations occurred with respect to the current scenario and prospectives. Results: There can be various possibilities in form of convalescent plasma therapy. The known drugs as HIV drugs, antimalarial medicines and antiviral compounds can serve as suggestive option. Conclusion: Till a confirm medicine or vaccine is sorted out for Covid-19, we need to take natural immune-boosters, along with precautionary steps, social distancing and other preventions as instructed for the benefit of everyone with an optimistic mind and attitude.



2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hanmo Li ◽  
Mengyang Gu

AbstractThe COVID-19 outbreak is asynchronous in US counties. Mitigating the COVID-19 transmission requires not only the state and federal level order of protective measures such as social distancing and testing, but also public awareness of time-dependent risk and reactions at county and community levels. We propose a robust approach to estimate the heterogeneous progression of SARS-CoV-2 at all US counties having no less than 2 COVID-19 associated deaths, and we use the daily probability of contracting (PoC) SARS-CoV-2 for a susceptible individual to quantify the risk of SARS-CoV-2 transmission in a community. We found that shortening by $$5\%$$ 5 % of the infectious period of SARS-CoV-2 can reduce around $$39\%$$ 39 % (or 78 K, $$95\%$$ 95 % CI: [66 K , 89 K ]) of the COVID-19 associated deaths in the US as of 20 September 2020. Our findings also indicate that reducing infection and deaths by a shortened infectious period is more pronounced for areas with the effective reproduction number close to 1, suggesting that testing should be used along with other mitigation measures, such as social distancing and facial mask-wearing, to reduce the transmission rate. Our deliverable includes a dynamic county-level map for local officials to determine optimal policy responses and for the public to better understand the risk of contracting SARS-CoV-2 on each day.



Author(s):  
Trang H.D. Nguyen

ABSTRACT While many nations are struggling to slow the transmission rate of the coronavirus disease 2019 (COVID-19), Vietnam has seen no new locally acquired cases since April 16. After implementing 22 d of nationwide social distancing, on April 23, the government of Vietnam announced the easing of social distancing measures. This allows the country to restart its socio-economic activities in a gradual, prudent manner. Domestic tourism and exports of agricultural and anti-COVID-19 medical products take priority over the other sectors in this postpandemic economic recovery. Importantly, the country needs to stay vigilant on the fight against the disease to prevent a possibility of another outbreak.



Author(s):  
Begüm Aylin Önder

Corporate social responsibility is one of the activities that goes beyond philanthropy, based on volunteerism in line with the responsibilities of enterprises towards society. This concept, which offers businesses the opportunity to look after and develop their brand image in the eyes of society, has become a necessity, not a choice, especially in today's world. In order to meet social expectations, the effectiveness of static and dynamic advertising messages implemented in all social benefit-based studies for human development such as environment, health and education is very important in terms of ensuring audience communication. In the second half of 2019, people were confined to homes and life came to a standstill all over the world in order to reduce and prevent the impact of the pandemic within the scope of the “New Type Corona Virus” (COVID-19) measures, which are from the sars-cov-2 coronavirus family, which is spreading rapidly globally starting from Wohan, Hubei Province, China. As a basic protection module for humanity against corona virus, it has incorporated the concept of social distancing into their lives in order to reduce the contact of staying at home and increasing hygiene, except in mandatory situations. During this extraordinary period, many brands on a global scale have included the concept of “social distance” in their advertising messages with the awareness of corporate social responsibility and have started to inform and educate the community about this issue by emphasizing the importance of the process. Within the scope of this research, advertising designs prepared by brands acting with corporate social responsibility awareness through the concept of social distancing during the Pandemic period were discussed and how the meaning structures behind the messages were created and transmitted. The research is limited to 3 (three) advertising designs determined by the 'judicial sampling' method (selective method). In the sample of the study, advertising narratives of brands in different sectors were explained in general framework and similar and different aspects of messages were uncovered by performing comparative analysis between messages in line with the findings obtained from the narratives. In this context, it was determined that the contrasts of “pessimism and optimism, hope and despair, happiness and unhappiness, death and life, strong and powerless, youth and old age, unity/togetherness and separation, struggle and defeat, nature and culture” were constructed as the main discourse.



2021 ◽  
Vol 121 (2) ◽  
pp. 33-47
Author(s):  
Alessandro M. Selvitella ◽  
Liam Carolan ◽  
Justin Smethers ◽  
Christopher Hernandez ◽  
Kathleen L. Foster

Understanding the initial growth rate of an epidemic is important for epidemiologists and policy makers as it can impact their mitigation strategies such as school closures, quarantines, or social distancing. Because the transmission rate depends on the contact rate of the susceptible population with infected individuals, similar growth rates might be experienced in nearby geographical areas. This research determined the growth rate of cases and deaths associated with COVID-19 in the early period of the 2020 pandemic in Ohio, United States. The evolution of cases and deaths was modeled through a Besag-York-Molliè model with linear- and power-type deterministic time dependence. The analysis showed that the growth rate of the time component of the model was subexponential in both cases and deaths once the time-lag across counties of the appearance of the first COVID-19 case was considered. Moreover, deaths in the northeast counties in Ohio were strongly related to the deaths in nearby counties.





1997 ◽  
Vol 48 (7) ◽  
pp. 989 ◽  
Author(s):  
W. Pathipanawat ◽  
R. A. C. Jones ◽  
K. Sivasithamparam

Factors likely to influence rates of transmission of alfalfa mosaic virus (AMV) through seed to seedlings of annual medics (Medicago spp.) and genetic control of the magnitude of its seed transmission rate were investigated in plants from 17 early-flowering accessions of M. polymorpha and in progenies of crosses involving M. murex cv. Zodiac × accession 5320 as parents. Plants were graft-inoculated when 6 weeks old to ensure successful and uniform infection. To exclude variation in seed transmission rates due to virus isolate or temperature, only 1 AMV isolate was used and the plants were kept under uniform temperature conditions. In M. polymorpha, significant differences were found between accessions in the levels of AMV transmitted through seed to progeny seedlings, SA 8250 giving the highest mean level of seed transmission (52%) and SA 4188 the lowest (3%). Neither virus concentration nor symptom severity influenced the rates of seed transmission obtained. However, part of the variation in seed transmission rates found in these accessions was related to their flowering times, seed transmission rates increasing as the interval between inoculation and owering increased. In seed samples collected from individual graft-inoculated plants of M. murex from (i) the F2 generation from crosses and reciprocal crosses, and (ii) the backcross progenies, the rates of transmission of AMV through seed to seedlings ranged from 0 to 77% and showed a continuous pattern of variation. Also, there was evidence of transgressive segregation for the low seed transmission rate condition. This indicates that the low seed transmission rate condition for AMV in medics is quantitatively inherited and under polygenic control. In contrast, when the pods from F2 progeny plants from the crosses and reciprocal crosses were examined, the segregation ratios obtained revealed that the smooth pod character from parent accession 5320 was controlled by a single recessive gene, for which the name sp is proposed. The presence in a plant of gene sp, or of its spiny pod-determining allele from the other parent cv. Zodiac, was not correlated with low seed transmission rates of AMV. It is concluded that selection for low rates of seed transmission and a population breeding approach can be used to produce improved M. polymorpha and M. murex cultivars with good resistance to seed-borne AMV





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