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1.
PLoS Comput Biol ; 18(7): e1010308, 2022 07.
Article in English | MEDLINE | ID: covidwho-1951512

ABSTRACT

The explosive outbreaks of COVID-19 seen in congregate settings such as prisons and nursing homes, has highlighted a critical need for effective outbreak prevention and mitigation strategies for these settings. Here we consider how different types of control interventions impact the expected number of symptomatic infections due to outbreaks. Introduction of disease into the resident population from the community is modeled as a stochastic point process coupled to a branching process, while spread between residents is modeled via a deterministic compartmental model that accounts for depletion of susceptible individuals. Control is modeled as a proportional decrease in the number of susceptible residents, the reproduction number, and/or the proportion of symptomatic infections. This permits a range of assumptions about the density dependence of transmission and modes of protection by vaccination, depopulation and other types of control. We find that vaccination or depopulation can have a greater than linear effect on the expected number of cases. For example, assuming a reproduction number of 3.0 with density-dependent transmission, we find that preemptively reducing the size of the susceptible population by 20% reduced overall disease burden by 47%. In some circumstances, it may be possible to reduce the risk and burden of disease outbreaks by optimizing the way a group of residents are apportioned into distinct residential units. The optimal apportionment may be different depending on whether the goal is to reduce the probability of an outbreak occurring, or the expected number of cases from outbreak dynamics. In other circumstances there may be an opportunity to implement reactive disease control measures in which the number of susceptible individuals is rapidly reduced once an outbreak has been detected to occur. Reactive control is most effective when the reproduction number is not too high, and there is minimal delay in implementing control. We highlight the California state prison system as an example for how these findings provide a quantitative framework for understanding disease transmission in congregate settings. Our approach and accompanying interactive website (https://phoebelu.shinyapps.io/DepopulationModels/) provides a quantitative framework to evaluate the potential impact of policy decisions governing infection control in outbreak settings.


Subject(s)
COVID-19 , COVID-19/epidemiology , COVID-19/prevention & control , Disease Outbreaks/prevention & control , Humans , Infection Control , Nursing Homes , Vaccination
2.
[Unspecified Source]; 2020.
Preprint in English | [Unspecified Source] | ID: ppcovidwho-292767

ABSTRACT

Background Large-scale school closures have been implemented worldwide to curb the spread of COVID-19. However, the impact of school closures and re-opening on epidemic dynamics remains unclear. Methods We simulated COVID-19 transmission dynamics using an individual-based stochastic model, incorporating social-contact data of school-aged children during shelter-in-place orders derived from Bay Area (California) household surveys. We simulated transmission under observed conditions and counterfactual intervention scenarios between March 17-June 1, and evaluated various fall 2020 K-12 reopening strategies. Findings Between March 17-June 1, assuming children <10 were half as susceptible to infection as older children and adults, we estimated school closures averted a similar number of infections (13,842 cases;95% CI: 6,290, 23,040) as workplace closures (15,813;95% CI: 9,963, 22,617) and social distancing measures (7,030;95% CI: 3,118, 11,676). School closure effects were driven by high school and middle school closures. Under assumptions of moderate community transmission, we estimate that fall 2020 school reopenings will increase symptomatic illness among high school teachers (an additional 40.7% expected to experience symptomatic infection, 95% CI: 1.9, 61.1), middle school teachers (37.2%, 95% CI: 4.6, 58.1), and elementary school teachers (4.1%, 95% CI: -1.7, 12.0). Results are highly dependent on uncertain parameters, notably the relative susceptibility and infectiousness of children, and extent of community transmission amid re-opening. The school-based interventions needed to reduce the risk to fewer than an additional 1% of teachers infected varies by grade level. A hybrid-learning approach with halved class sizes of 10 students may be needed in high schools, while maintaining small cohorts of 20 students may be needed for elementary schools. Interpretation Multiple in-school intervention strategies and community transmission reductions, beyond the extent achieved to date, will be necessary to avoid undue excess risk associated with school reopening. Policymakers must urgently enact policies that curb community transmission and implement within-school control measures to simultaneously address the tandem health crises posed by COVID-19 and adverse child health and development consequences of long-term school closures.

3.
JCI Insight ; 6(14)2021 07 22.
Article in English | MEDLINE | ID: covidwho-1320462

ABSTRACT

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a pandemic. Severe disease is associated with dysfunction of multiple organs, but some infected cells do not express ACE2, the canonical entry receptor for SARS-CoV-2. Here, we report that the C-type lectin receptor L-SIGN interacted in a Ca2+-dependent manner with high-mannose-type N-glycans on the SARS-CoV-2 spike protein. We found that L-SIGN was highly expressed on human liver sinusoidal endothelial cells (LSECs) and lymph node lymphatic endothelial cells but not on blood endothelial cells. Using high-resolution confocal microscopy imaging, we detected SARS-CoV-2 viral proteins within the LSECs from liver autopsy samples from patients with COVID-19. We found that both pseudo-typed virus enveloped with SARS-CoV-2 spike protein and authentic SARS-CoV-2 virus infected L-SIGN-expressing cells relative to control cells. Moreover, blocking L-SIGN function reduced CoV-2-type infection. These results indicate that L-SIGN is a receptor for SARS-CoV-2 infection. LSECs are major sources of the clotting factors vWF and factor VIII (FVIII). LSECs from liver autopsy samples from patients with COVID-19 expressed substantially higher levels of vWF and FVIII than LSECs from uninfected liver samples. Our data demonstrate that L-SIGN is an endothelial cell receptor for SARS-CoV-2 that may contribute to COVID-19-associated coagulopathy.


Subject(s)
COVID-19 , Capillaries , Cell Adhesion Molecules/metabolism , Endothelial Cells , Lectins, C-Type/metabolism , Liver/blood supply , Lymphatic Vessels , Receptors, Cell Surface/metabolism , SARS-CoV-2/physiology , COVID-19/metabolism , COVID-19/pathology , COVID-19/virology , Capillaries/metabolism , Capillaries/pathology , Capillaries/virology , Endothelial Cells/metabolism , Endothelial Cells/pathology , Endothelial Cells/virology , Gene Expression Profiling/methods , Humans , Liver/pathology , Lymphatic Vessels/metabolism , Lymphatic Vessels/pathology , Lymphatic Vessels/virology , Spike Glycoprotein, Coronavirus , Virus Internalization
4.
J R Soc Interface ; 18(177): 20200970, 2021 04.
Article in English | MEDLINE | ID: covidwho-1183109

ABSTRACT

School closures may reduce the size of social networks among children, potentially limiting infectious disease transmission. To estimate the impact of K-12 closures and reopening policies on children's social interactions and COVID-19 incidence in California's Bay Area, we collected data on children's social contacts and assessed implications for transmission using an individual-based model. Elementary and Hispanic children had more contacts during closures than high school and non-Hispanic children, respectively. We estimated that spring 2020 closures of elementary schools averted 2167 cases in the Bay Area (95% CI: -985, 5572), fewer than middle (5884; 95% CI: 1478, 11.550), high school (8650; 95% CI: 3054, 15 940) and workplace (15 813; 95% CI: 9963, 22 617) closures. Under assumptions of moderate community transmission, we estimated that reopening for a four-month semester without any precautions will increase symptomatic illness among high school teachers (an additional 40.7% expected to experience symptomatic infection, 95% CI: 1.9, 61.1), middle school teachers (37.2%, 95% CI: 4.6, 58.1) and elementary school teachers (4.1%, 95% CI: -1.7, 12.0). However, we found that reopening policies for elementary schools that combine universal masking with classroom cohorts could result in few within-school transmissions, while high schools may require masking plus a staggered hybrid schedule. Stronger community interventions (e.g. remote work, social distancing) decreased the risk of within-school transmission across all measures studied, with the influence of community transmission minimized as the effectiveness of the within-school measures increased.


Subject(s)
COVID-19 , Child , Humans , Physical Distancing , Policy , SARS-CoV-2 , Schools
5.
Open Forum Infect Dis ; 8(2): ofab023, 2021 Feb.
Article in English | MEDLINE | ID: covidwho-1039750

ABSTRACT

BACKGROUND: Rapid coronavirus disease 2019 (COVID-19) diagnosis and isolation of infectious persons are critical to stopping forward transmission, and the care cascade framework can identify gaps in the COVID-19 response. METHODS: We described a COVID-19 symptom to isolation cascade and barriers among symptomatic persons who tested polymerase chain reaction positive for severe acute respiratory disease coronavirus 2 (SARS-CoV-2) at a low-barrier testing site serving a low-income Latinx community in San Francisco. Steps in the cascade are defined as days from symptom onset to test, test to result, and result to counseling on self-isolation. We examined SARS-CoV-2 cycle threshold (Ct) values to assess the likelihood of infectiousness on the day of testing and during missed isolation days. RESULTS: Among 145 persons, 97% were Latinx and 81% had an income of <$50 000. The median time from symptom onset to isolation (interquartile range [IQR]) was 7 (5-10) days, leaving a median (IQR) of 3 (0-6) days of isolation. Eighty-three percent had moderate to high levels of virus (Ct <33), but by disclosure 23% were out of their isolation period. The longest intervals were symptom onset to test (median [IQR], 4 [2-9] days) and test to results notification (median [IQR], 3 [2-4] days). Access to a test site was the most common barrier to testing, and food and income loss was the most common barrier to isolation. CONCLUSIONS: Over half of the 10-day isolation period passed by the time of disclosure, and over a fifth of people were likely outside the window of infectiousness by the time they received results. Improvements in test access and turnaround time, plus support for isolation, are needed for epidemic control of SARS-CoV-2 in highly impacted communities.

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