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Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19.

ABSTRACT: A key parameter in epidemiological modeling which characterizes the spread of an infectious disease is the generation time, or more generally the distribution of infectiousness as a function of time since infection. There is increasing evidence supporting a prolonged viral shedding window for COVID-19, but the transmissibility in this phase is unclear. Based on this, we develop a generalized Susceptible-Exposed-Infected-Resistant (SEIR) model including an additional compartment of chronically infected individuals who can stay infectious for a longer duration than the reported generation time, but with infectivity reduced to varying degrees. Using the incidence and fatality data from different countries, we first show that such an assumption also yields a plausible model in explaining the data observed prior to the easing of the lockdown measures (relaxation). We then test the predictive power of this model for different durations and levels of prolonged infectiousness using the incidence data after the introduction of relaxation in Switzerland, and compare it with a model without the chronically infected population to represent the models conventionally used. We show that in case of a gradual easing on the lockdown measures, the predictions of the model including the chronically infected population vary considerably from those obtained under a model in which prolonged infectiousness is not taken into account. Although the existence of a chronically infected population still remains largely hypothetical, we believe that our results provide tentative evidence to consider a chronically infected population as an alternative modeling approach to better interpret the transmission dynamics of COVID-19.

SUBMITTER: Tepekule B

PROVIDER: S-EPMC7875355 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19.

Tepekule Burcu B Hauser Anthony A Kachalov Viacheslav N VN Andresen Sara S Scheier Thomas T Schreiber Peter W PW Günthard Huldrych F HF Kouyos Roger D RD

PLoS computational biology 20210129 1

A key parameter in epidemiological modeling which characterizes the spread of an infectious disease is the generation time, or more generally the distribution of infectiousness as a function of time since infection. There is increasing evidence supporting a prolonged viral shedding window for COVID-19, but the transmissibility in this phase is unclear. Based on this, we develop a generalized Susceptible-Exposed-Infected-Resistant (SEIR) model including an additional compartment of chronically in ...[more]

PMID: 33513139

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Project description:BackgroundBovine coronavirus (BCoV) is a widely distributed pathogen, causing disease and economic losses in the cattle industry worldwide. Prevention of virus spread is impeded by a lack of basic knowledge concerning viral shedding and transmission potential in individual animals. The aims of the study were to investigate the duration and quantity of BCoV shedding in feces and nasal secretions related to clinical signs, the presence of virus in blood and tissues and to test the hypothesis that seropositive calves are not infectious to naïve in-contact calves three weeks after BCoV infection.MethodsA live animal experiment was conducted, with direct contact between animal groups for 24 h as challenge procedure. Four naïve calves were commingled with a group of six naturally infected calves and sequentially euthanized. Two naïve sentinel calves were commingled with the experimentally exposed group three weeks after exposure. Nasal swabs, feces, blood and tissue samples were analyzed for viral RNA by RT-qPCR, and virus isolation was performed on nasal swabs. Serum was analyzed for BCoV antibodies.ResultsThe calves showed mild general signs, and the most prominent signs were from the respiratory system. The overall clinical score corresponded well with the shedding of viral RNA the first three weeks after challenge. General depression and cough were the signs that correlated best with shedding of BCoV RNA, while peak respiratory rate and peak rectal temperature appeared more than a week later than the peak shedding. Nasal shedding preceded fecal shedding, and the calves had detectable amounts of viral RNA intermittently in feces through day 35 and in nasal secretions through day 28, however virus isolation was unsuccessful from day six and day 18 from the two calves investigated. Viral RNA was not detected in blood, but was found in lymphatic tissue through day 42 after challenge. Although the calves were shedding BCoV RNA 21 days after infection the sentinel animals were not infected.ConclusionsProlonged shedding of BCoV RNA can occur, but detection of viral RNA does not necessarily indicate a transmission potential. The study provides valuable information with regard to producing scientifically based biosecurity advices.

Project description:Background and aimsThe COVID-19 pandemic has resulted in associated lockdown restrictions for individuals across England, including the postponement of all recreational sporting provisions. The beneficial effects of regular physical activity are well established yet to the authors' knowledge, no research addresses the cancellation of all recreational provisions. Using quantitative and qualitative methods, this study assessed the impact of COVID-19 restrictions on recreational sports players, what alternative exercise methods have been sought and how players feel about returning to their sport.MethodAn online survey was distributed across England for six-weeks commencing in May 2020. A questionnaire explored differences in the impact of COVID-19 restrictions between sex, winter/summer/year-round sports, team/individual sports, age, and resilience groups. The use of alternative exercise methods, coping strategies and feelings about returning to sport were also investigated. Responses were gathered from 2023 adults whose recreational sport had been cancelled by COVID-19. All completed questionnaires (n = 1213) were taken for analysis (mean age = 49.41 years, SD = 17.165, 55.2% female).ResultsQuantitative findings showed the negative impact of COVID-19 restrictions was greater for females, those involved in winter and team sports, those aged 18-39 and low-resilient copers (p < .05). No significant differences were found between individuals that had had COVID-19 or were considered vulnerable by government guidelines. Acceptance was the most common coping strategy. The average number of days per week that participants exercised significantly increased during lockdown, with significant increases also seen in the use of online workouts, fitness apps and home-gym exercise. Qualitative findings suggested that participants are looking forward to the social and physical benefits of recreational activity restarting yet are concerned about the logistics of returning under social distancing restrictions. Other worries included loss of fitness, spreading (younger age groups) and catching (older age groups) COVID-19 and being in a crowd.ConclusionsResults highlight what is currently accessible to home-based exercisers and inform the reintroduction of recreational sports clubs. As COVID-19 restrictions look to persist, club representatives should provide accessible home-exercise options and be cautious of participant concerns when considering the return of recreational sport.

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Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19.

Publications

Assessing the potential impact of transmission during prolonged viral shedding on the effect of lockdown relaxation on COVID-19.

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