#Individual #quarantine versus active #monitoring of #contacts for the #mitigation of #COVID19: a modelling study (Lancet Infect Dis., abstract)

[Source: Lancet Infectious Diseases, full page: (LINK). Abstract, edited.]

Individual quarantine versus active monitoring of contacts for the mitigation of COVID-19: a modelling study

Corey M Peak, ScD, Rebecca Kahn, MS, Yonatan H Grad, MD, Lauren M Childs, PhD, Ruoran Li, Mphil, Prof Marc Lipsitch, Dphil, Caroline O Buckee, Dphil

Published: May 20, 2020 | DOI: https://doi.org/10.1016/S1473-3099(20)30361-3




Voluntary individual quarantine and voluntary active monitoring of contacts are core disease control strategies for emerging infectious diseases such as COVID-19. Given the impact of quarantine on resources and individual liberty, it is vital to assess under what conditions individual quarantine can more effectively control COVID-19 than active monitoring. As an epidemic grows, it is also important to consider when these interventions are no longer feasible and broader mitigation measures must be implemented.


To estimate the comparative efficacy of individual quarantine and active monitoring of contacts to control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we fit a stochastic branching model to reported parameters for the dynamics of the disease. Specifically, we fit a model to the incubation period distribution (mean 5·2 days) and to two estimates of the serial interval distribution: a shorter one with a mean serial interval of 4·8 days and a longer one with a mean of 7·5 days. To assess variable resource settings, we considered two feasibility settings: a high-feasibility setting with 90% of contacts traced, a half-day average delay in tracing and symptom recognition, and 90% effective isolation; and a low-feasibility setting with 50% of contacts traced, a 2-day average delay, and 50% effective isolation.


Model fitting by sequential Monte Carlo resulted in a mean time of infectiousness onset before symptom onset of 0·77 days (95% CI −1·98 to 0·29) for the shorter serial interval, and for the longer serial interval it resulted in a mean time of infectiousness onset after symptom onset of 0·51 days (95% CI −0·77 to 1·50). Individual quarantine in high-feasibility settings, where at least 75% of infected contacts are individually quarantined, contains an outbreak of SARS-CoV-2 with a short serial interval (4·8 days) 84% of the time. However, in settings where the outbreak continues to grow (eg, low-feasibility settings), so too will the burden of the number of contacts traced for active monitoring or quarantine, particularly uninfected contacts (who never develop symptoms). When resources are prioritised for scalable interventions such as physical distancing, we show active monitoring or individual quarantine of high-risk contacts can contribute synergistically to mitigation efforts. Even under the shorter serial interval, if physical distancing reduces the reproductive number to 1·25, active monitoring of 50% of contacts can result in overall outbreak control (ie, effective reproductive number <1).


Our model highlights the urgent need for more data on the serial interval and the extent of presymptomatic transmission to make data-driven policy decisions regarding the cost–benefit comparisons of individual quarantine versus active monitoring of contacts. To the extent that these interventions can be implemented, they can help mitigate the spread of SARS-CoV-2.


National Institute of General Medical Sciences, National Institutes of Health.

Keywords: SARS-CoV-2; COVID-19; Quarantine.


Modeling the #effects of #intervention #strategies on #COVID19 #transmission dynamics (J Clin Virol., abstract)

[Source: Journal of Clinical Virology, full page: (LINK). Abstract, edited.]

Journal of Clinical Virology | Available online 15 May 2020, 104440 | In Press, Journal Pre-proof

Modeling the effects of intervention strategies on COVID-19 transmission dynamics

Deanna M. Kennedy a, Gustavo José Zambrano b, Yiyu Wang a, Osmar Pinto Neto b,c,d

a Texas A&M University, Department of Health and Kinesiology, TX, USA; b Anhembi Morumbi University, Biomedical Engineering Department, São Paulo, SP, Brazil; c Arena235 Research Lab – São José dos Campos, SP, Brazil; d Center for Innovation, Technology and Education – CITE, Parque Tecnológico de São José dos Campos, São José dos Campos, SP, Brazil

Received 9 May 2020, Accepted 10 May 2020, Available online 15 May 2020.

DOI: https://doi.org/10.1016/j.jcv.2020.104440



  • A susceptible, unsusceptible, exposed, infected, hospitalized, critical, dead, and recovered (SUEIHCDR) epidemiological compartmental model was used to simulate social distancing scenarios in the United States.
  • The model results provide specific guidelines to increase the probability of containing the pandemic at manageable levels with minimal impact on human life.
  • If people exercise caution while in public by protecting themselves (e.g., wearing a facemask, proper hand hygiene, avoiding agglomerations) the magnitude and duration of social distancing necessary to maintain control over the pandemic can be reduced.
  • Our models suggest that the most effective way to reduce SD over a two-year period is a stepping-down approach with steps every 80 days.




To model the effects of continuous, intermittent, and stepping-down social distancing (SD) strategies and personal protection measures on COVID-19 transmission dynamics.


Constant, intermittent, and stepping-down SD strategies were modeled at 4 mean magnitudes (5%, 10%, 15% and 20%), 2 time windows (40-days, 80-days), and 2 levels of personal caution (30% and 50%).


The stepping-down strategy was the best long-term SD strategy to minimize the peak number of active COVID-19 cases and associated deaths. The stepping-down strategy also resulted in a reduction in total time required to SD over a two-year period by 6.5% compared to an intermittent or constant SD strategy. An 80-day SD time-window was statistically more effective in maintaining control over the COVID-19 pandemic than a 40-day window. However, the results were dependent upon 50% of people being cautious (engaging in personal protection measures).


If people exercise caution while in public by protecting themselves (e.g., wearing a facemask, proper hand hygiene and avoid agglomeration) the magnitude and duration of SD necessary to maintain control over the pandemic can be reduced. Our models suggest that the most effective way to reduce SD over a two-year period is a stepping-down approach every 80 days. According to our model, this method would prevent a second peak and the number of intensive care units needed per day would be within the threshold of those currently available.

Keywords: SARS-CoV-2; COVID-19; Quarantine.


Voluntary #collective #isolation as a best response to #COVID19 for #indigenous populations? A case study and protocol from the #Bolivian #Amazon (Lancet, abstract)

[Source: Lancet, full page: (LINK). Abstract, edited.]

Voluntary collective isolation as a best response to COVID-19 for indigenous populations? A case study and protocol from the Bolivian Amazon

Prof Hillard S Kaplan, PhD, Benjamin C Trumble, PhD, Jonathan Stieglitz, PhD, Roberta Mendez Mamany, Maguin Gutierrez Cayuba, Leonardina Maito Moye, Lic, Sarah Alami, MA, Thomas Kraft, PhD, Raul Quispe Gutierrez, MD, Juan Copajira Adrian, MD, Prof Randall C Thompson, MD, Prof Gregory S Thomas, MD, David E Michalik, DO, Daniel Eid Rodriguez, MD, Prof Michael D Gurven, PhD

Published: May 15, 2020 | DOI: https://doi.org/10.1016/S0140-6736(20)31104-1



Indigenous communities worldwide share common features that make them especially vulnerable to the complications of and mortality from COVID-19. They also possess resilient attributes that can be leveraged to promote prevention efforts. How can indigenous communities best mitigate potential devastating effects of COVID-19? In Bolivia, where nearly half of all citizens claim indigenous origins, no specific guidelines have been outlined for indigenous communities inhabiting native communal territories. In this Public Health article, we describe collaborative efforts, as anthropologists, physicians, tribal leaders, and local officials, to develop and implement a multiphase COVID-19 prevention and containment plan focused on voluntary collective isolation and contact-tracing among Tsimane forager-horticulturalists in the Bolivian Amazon. Phase 1 involves education, outreach, and preparation, and phase 2 focuses on containment, patient management, and quarantine. Features of this plan might be exported and adapted to local circumstances elsewhere to prevent widespread mortality in indigenous communities.

Keywords: SARS-CoV-2; COVID-19; Bolivia; Society; Poverty.


#Reopening #Society and the Need for Real-Time #Assessment of #COVID19 at the #Community Level (JAMA, summary)

[Source: JAMA, full page: (LINK). Summary, edited.]

Reopening Society and the Need for Real-Time Assessment of COVID-19 at the Community Level

Frederick J. Angulo, DVM, PhD1; Lyn Finelli, DrPH, MS2; David L. Swerdlow, MD1

Author Affiliations: 1 Medical Development and Scientific/Clinical Affairs, Pfizer Vaccines, Collegeville, Pennsylvania; 2 Center for Observational and Real-World Evidence, Merck & Co Inc, Kenilworth, New Jersey

JAMA. Published online May 15, 2020. doi:10.1001/jama.2020.7872


Through May 13, 2020, approximately 1.39 million cases of coronavirus disease 2019 (COVID-19) have been reported in the United States (by the Centers for Disease Control and Prevention) and more than 4.3 million cases of COVID-19 have been reported from 188 countries.1 There is an urgent need for COVID-19 data, including community-level incidence, spectrum of disease, diagnostic test penetration, and proportion of the community with protective immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (herd immunity). These data are vital to understanding where communities are on the continuum of COVID-19 cumulative incidence and prevalence and how nonpharmaceutical interventions can be titrated to reopen business and society. Real-time incidence and seroepidemiologic data are also essential to plan scenarios for the development of COVID-19 vaccines and therapeutics. Cross-sectional community surveys combined with seroepidemiology can help inform the present and help navigate the path forward.


Keywords: SARS-CoV-2; COVID-19; Quarantine.


Effective #containment explains #subexponential #growth in recent confirmed #COVID19 cases in #China (Science, abstract)

[Source: Science, full page: (LINK). Abstract, edited.]

Effective containment explains subexponential growth in recent confirmed COVID-19 cases in China

Benjamin F. Maier1,*, Dirk Brockmann1,2

1 Robert Koch Institute, Nordufer 20, D-13353 Berlin, Germany. 2 Institute for Theoretical Biology, Humboldt University of Berlin, Philippstrasse 13, D-10115 Berlin, Germany.

*Corresponding author. Email: bfmaier@physik.hu-berlin.de

Science  15 May 2020: Vol. 368, Issue 6492, pp. 742-746 | DOI: 10.1126/science.abb4557


Containment works

National governments have taken different approaches in response to the coronavirus disease 2019 (COVID-19) pandemic, ranging from draconian quarantines to laissez-faire mitigation strategies. In data from China collected in February 2020, Maier and Brockmann noticed that, unexpectedly, the epidemic did not take off exponentially. Nonexponential spread occurs when the supply of susceptible individuals is depleted on a time scale comparable to the infectious period of the virus. The results of the authors’ modeling approach indicate that the public response to the epidemic plus containment policies were becoming effective despite the initial increase in confirmed cases.

Science, this issue p. 742



The recent outbreak of coronavirus disease 2019 (COVID-19) in mainland China was characterized by a distinctive subexponential increase of confirmed cases during the early phase of the epidemic, contrasting with an initial exponential growth expected for an unconstrained outbreak. We show that this effect can be explained as a direct consequence of containment policies that effectively deplete the susceptible population. To this end, we introduce a parsimonious model that captures both quarantine of symptomatic infected individuals, as well as population-wide isolation practices in response to containment policies or behavioral changes, and show that the model captures the observed growth behavior accurately. The insights provided here may aid the careful implementation of containment strategies for ongoing secondary outbreaks of COVID-19 or similar future outbreaks of other emergent infectious diseases.

Keywords: SARS-CoV-2; COVID-19; Quarantine; China.


#Changes in #SARS-CoV-2 #Positivity #Rate in #Outpatients in #Seattle and #Washington State, March 1-April 16, 2020 (JAMA, summary)

[Source: JAMA, full page: (LINK). Summary, edited.]

Changes in SARS-CoV-2 Positivity Rate in Outpatients in Seattle and Washington State, March 1-April 16, 2020

April Kaur Randhawa, PhD1; Leigh H. Fisher, PhD1; Alexander L. Greninger, MD, PhD2; et al. Shuying Sue Li, PhD1; Jessica Andriesen, PhD1; Lawrence Corey, MD1; Keith R. Jerome, MD, PhD2

Author Affiliations: 1 Division of Vaccine and Infectious Disease, Fred Hutchinson Cancer Research Center, Seattle, Washington; 2 Department of Laboratory Medicine, University of Washington School of Medicine, Seattle

JAMA. Published online May 8, 2020. doi:10.1001/jama.2020.8097


The first reported case of coronavirus disease 2019 (COVID-19) in the US occurred on January 20, 2020, in Snohomish County, Washington.1 The University of Washington (UW) Virology Division was among the first US laboratories to test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and since March 1, 2020, has tested samples from more than 73 000 patients. More than 90% of the samples are from the UW health system and outpatient clinics in Washington State. The positivity rates for SARS-CoV-2 in outpatient settings in Washington State and in emergency departments (EDs) in Seattle were analyzed to identify temporal trends that may reflect the local dynamics of the pandemic and the effect of mitigation strategies such as physical distancing.


Keywords: SARS-CoV-2; COVID-19; USA; Washington State; Quarantine.


#Suppressing the #Epidemic in #NSW (N Engl J Med., summary)

[Source: The New England Journal of Medicine, full page: (LINK). Summary, edited.]

Suppressing the Epidemic in New South Wales


To rapidly communicate short reports of innovative responses to Covid-19 around the world, along with a range of current thinking on policy and strategy relevant to the pandemic, the Journal has initiated the Covid-19 Notes series.


Facing the coronavirus pandemic, Australia has achieved national consensus on policies that were unprecedented for the past century. New South Wales (which has 8 million residents) and other jurisdictions appear to have successfully suppressed Covid-19 transmission after a rapid escalation of cases in March 2020.


Keywords: SARS-CoV-2; COVID-19; Australia; NSW.