For example, we do not explicitly model the dynamics of certain institutions that have been particularly hard-hit by COVID-19, such as retirement homes and long-term care facilities [77], prisons [78,79], and homeless shelters [80]. Because of that, large antennas should be tested at times when propagated signals in the range of the antenna's response are at minimum strength. so we can do more of it. We found that these household-merging strategies could be safe only if a few criteria were met. In this study we use a mathematical model to simulate the spread and control of COVID-19, tracking the different settings of person-to-person contact (e.g. Intervention is very effective at suppressing external transmission and so, even though household transmission continues during intervention it can not spill over between households. In each layer, the degree distribution and level of clustering were chosen to match data. The overlap in symptoms with many endemic and milder respiratory infections—such as influenza, parainfluenza, respiratory syncytial virus, and seasonal coronaviruses—make syndromic identification of cases difficult. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Direct Connect gateway can dynamically propagate routes to a transit gateway route These effects are exacerbated if we assume household transmission rates (contact weights) can increase post-intervention (Fig 3J). Under a 100% effective intervention (Fig 4A), the delays to peaks were driven mainly by the clinical progression alone, similar to the case of the well-mixed population, but were slightly extended due to residual spread restricted to a single household. One limitation of these sorts of surveys is that they are “ego-centric”, meaning that they only inform the distribution of the number of contacts but not the higher order network structure, which can be important for infection spread [26,47]. The supra-linear increase in risk with household size is driven by the fact that in larger households there is both more risk of seeding of infection from outside, as well as more individuals to spread to within the household leading to less chance of extinction of spread. Our results are not sensitive to our assumptions about the fraction of cases that progress to more serious clinical stages nor to the case fatality risk. You are charged hourly for each attachment on a transit gateway, and you are charged There are several reasons why we believe those estimates are likely a little too low. MTU of a A transit gateway To enable catching and handling errors in a try-catch block. By varying the relative weight of household vs external contacts, our study examined a range of household secondary attack rates from ~10% to ~65%. https://doi.org/10.1371/journal.pcbi.1008684.s003. These measures have been applied around the world, but in situations where they have suppressed infections, the effect has not been immediate or consistent. Amazon VPC, but it requires that your application handle low-level details such as We consider various scenarios for the efficacy of interventions in reducing contacts, heterogeneities in their adoption in different demographic groups, the relative role of transmission in different settings, and the timing of partial or complete relaxation of isolation measures. We repeated these simulations with a hierarchically-clustered external layer (see Methods) to check the robustness of the trends to details in the large-scale clustering of the transmission network (S1 and S2 Figs). The goal of this paper was to understand whether the clinical progression of COVID-19 and transmission network structure could explain these types of post-intervention dynamics. Bottom row: The first timepoint after the intervention that Rt <1. Firstly, they must be applied in the context of steadily declining cases and deaths (Fig 7B and 7D). Software, you Moreover, we find that the amount of transmission that happens within versus outside the household is critical to determining when social distancing can be effective and the delay until the epidemic peak. Calibration of instruments (including adjustment) in the present context are also referred to as standardization. School and work layers consisted of connections between individuals only belonging to the school-aged and working-aged groups respectively. We assume that cases are diagnosed only at the time of hospitalization. Liu et al considered a collection of known clusters involving close contacts in a single gathering (not just household, often group meals), and estimated a 35% secondary attack rate. You can create, access, and manage your transit gateways using any of the following We hope that by providing our code, researchers who are interested in specific contexts where these values may differ significantly can explore those scenarios. Black dotted line shows the time the intervention began. that are linked together so they can communicate. In both cases, all school connections were deleted post-intervention and 70% of connections were uniformly deleted at random in the social and community layers. enabled. No, PLOS is a nonprofit 501(c)(3) corporation, #C2354500, based in San Francisco, California, US, https://doi.org/10.1371/journal.pcbi.1008684, https://github.com/alsnhll/COVID19NetworkSimulations, http://www.imperial.ac.uk/medicine/departments/school-public-health/infectious-disease-epidemiology/mrc-global-infectious-disease-analysis/covid-19/report-23-united-states/, https://www.ilo.org/wcmsp5/groups/public/@dgreports/@dcomm/documents/briefingnote/wcms_755910.pdf, https://www.imf.org/en/Publications/WEO/Issues/2020/06/24/WEOUpdateJune2020, https://www.washingtonpost.com/world/the_americas/coronavirus-canada-new-brunswick-newfoundland-double-bubble/2020/05/07/78e08960-8eec-11ea-9322-a29e75effc93_story.html, https://news.gallup.com/poll/307760/three-four-self-isolated-household.aspx, https://news.gallup.com/opinion/gallup/308444/americans-social-contacts-during-covid-pandemic.aspx, https://www.google.com/covid19/mobility?hl, https://www.cuebiq.com/visitation-insights-covid19/, https://covid19.gleamproject.org/mobility, https://cmmid.github.io/topics/covid19/current-patterns-transmission/global-time-varying-transmission.html, https://www.themarshallproject.org/2020/05/01/a-state-by-state-look-at-coronavirus-in-prisons. No, Is the Subject Area "Public and occupational health" applicable to this article? connection, the more data that can be passed in a single packet. Yes qWireless link transmission errors isolated from those in fixed n etwork qsimple to control, mobile TCP is used only for one hop between, e.g., a foreign agent and mobile host qtherefore, a very fast retransmission of packets is possible, the short delay on the mobile hop is known Disadvantages This stage lasts ~ 1 week and individuals are infectious for this duration. Elsewhere schools and universities have been closed, international travel has been limited, restaurants and retailers shuttered, mask-wearing encouraged or required, and stay-at-home orders put in place. In all plots, household and external contacts have equal weight. In all scenarios the overall infection prevalence at the time intervention was started was identical. supports an MTU Roles We're If even a small fraction of households have been “seeded” with infection at the time an intervention is implemented, cases may continue to increase for multiple serial intervals. These results were exacerbated if we assumed that the importance of household contacts increased post-intervention (Fig 4C), due to increased time spent in close quarters. Using Google data they concluded that in the US, initial emergency declarations lead to ~10% reductions, that each additional policy led to another ~20% reduction, and that “shelter-in-place” orders resulted in additional ~30% reductions [64]. The first three quantities are peak prevalence levels (I1, I2, I3), while the latter two are daily incidence values. With a Connect attachment, the routes are propagated to a transit gateway route table In the US, nationally-representative polls in late March/early April found that around three quarters of households were self-isolating [54], and estimated a mean reduction in contacts around 80% [55,56]. The number of contacts alone was not very informative for predicting intervention efficacy. attachment. However, the qualitative finding that peaks in case counts, hospitalizations, and deaths can be significantly delayed beyond when an intervention is implemented is a general finding for models tracking the natural history of COVID-19. Wellenius et al attempted to infer the association between these mobility reductions and the particular social distancing policies that caused them. Each household belongs to a mutually-exclusive “neighborhood”, and external connections are preferentially created within the same neighborhood. To use the AWS Documentation, Javascript must be Lewis et al find a rate of 28% in Wisconsin and Utah [41], while Grijalva et al found 53% in Wisconsin and Tennessee [42]. Colors of nodes represent four broad age groups that determine network membership and structure: preschool-aged (pink), school-aged (purple), working-aged (blue) and elderly (green). No, Is the Subject Area "Social policy" applicable to this article? Thanks for letting us know we're doing a good To examine when this strategy could be safely implemented without risking a rebound in cases, we randomly joined households 1, 2, or 3 months after the implementation of a strong social distancing measure (80 or 90% effective) (Fig 7). Data curation, Top row: Simulated time course of different clinical stages of infection under an intervention (first black dashed line) that reduces external contacts by 80%, for different values of the relative weight of external contacts. In reality, human contact networks tend to be highly structured, with groups of individuals with high levels of interconnectedness and large variation between individuals in total contacts (e.g. https://doi.org/10.1371/journal.pcbi.1008684.g006. AWS Transit Gateway pricing. FEC is a method that enables a receiver to not only detect, but also correct errors in a transmission. Strong social distancing measures tend to be economically costly and in most regions of the world these measures were relaxed to some extent after a few months. For a less effective intervention, the difference in outcomes for the two deletion schemes was more prominent (S3 Fig). The daily incidence of new deaths didn’t peak for ~ 10 weeks. The networks we use to simulate infection were parameterized based on detailed surveys that used “contact diaries” to track the number of individuals someone interacted with on a randomly chosen day [20,21]. Amazon EC2 API Reference. We assumed that during a social distancing measure, school contacts were completely removed, and that work, social, and other contacts were reduced by an amount equal to the intervention efficacy. Another factor is that there could be a delay between implementation of distancing measures and adoption by a majority of the population. Third row: Same but using the daily incidence of new hospitalizations (I2). Under more extreme distancing (~85% reduction in contacts), the relative risk of infection among workers relative to the population average was 1.6, while for individuals not working themselves but living in the same household as someone who was working was 1.4. Bottom row: External contacts for individuals were reduced after two households were merged, such that overall number of contacts remained unchanged. For work contacts, we also considered the case where edges weren’t removed at random, but instead, certain “workplaces” were completely dissolved, whereas others remained (Fig 5C, top). A review by Lan et al of case reports within the first month of the outbreak in multiple countries found that about 15% of these cases were clearly work-related, and that even earlier in the outbreak, this was as high as 50% [66]. A unique feature of our model is that it simultaneously captures the clinical progression of COVID-19 (as opposed to simpler SEIR models), a reasonable approximation of contact network structure (as opposed to well-mixed models), and realistic distributions of the durations of states (as opposed to continuous-transition models which assume exponentially-distributed durations, and lead to unrealistically long tails in infection after strong interventions). Publish and Subscribe Model. A “worker” is defined as someone with an occupation in which they continue to work outside the home despite social distancing measures. job! Funding acquisition, External connections were constructed by connecting individuals to people in other households. We combine this with data-driven transmission networks that explicitly consider household vs external contacts and how they are differentially altered by social distancing measures. However, we found that the time until infection was eliminated from the population was much longer: increasing from ~ 180 days to ~ 220 days for population sizes of a million. In addition, we examined the impact that the increased time spent with household members (and hence an increased transmission potential) after stay-at-home policies begin could have on the outcome of an intervention and the timescale for disease elimination (Fig 3). Separate assumptions of our modeling approach could lead our predictions to be slightly pessimistic. For example, individuals may spend 8–10 hours a day with coworkers or classmates, but only a few waking hours with household members, and so external contact could have higher weights. Doctors, nurses, and other health professionals are reported to make up 5–10% of cases in some regions, and while increased testing is likely one factor driving these rates, it is clear that there are also unique risks to this profession. Traffic over VPN connections can have an MTU of 1500 bytes. connection or a Direct Connect gateway, routes are propagated from the transit gateway For an 80% effective intervention, the final epidemic size can be 5–10—fold higher than expected due to increased chance of within-household transmission. In addition, social distancing measures reduce transmission outside the household, but in general they involve isolating individuals within their normal places of residence and thus do not prevent household transmission. The economic recession in the US has led to massive increases in households at risk of eviction, and separate work using a similar model found that evictions could result in substantial increases in cases across cities if the current eviction bans expire [81]. For more information, see AWS Transit Gateway. Therefore, interleaving is widely used for burst error-correction. Individuals have contacts within their households and with others outside the household, which preferentially occur within a local neighborhood (S1 Fig). Under clustered adoption, the epidemic plateaued and took much longer to decline compared to the case of uniform adoption where decline began immediately. Based on large-scale contact surveys and other modeling studies [20,21,25–27], we broke down external contacts into four different layers—school, work, social and community (Fig 5A). The maximum transmission unit (MTU) of a network connection is the size, in bytes, We consider a region where infections are only counted upon hospitalization (progression to severe class), and then find that peak incidence of cases occurs 7 and 11 days after an intervention that is 100% or 70% effective. 5. The economic and social costs of these measures are immense: unemployment has surged, stock markets have plummeted, delivery of healthcare for non-COVID-19 conditions has been interrupted [15–19]. We found that the trends were unaffected independent of whether the merged households belonged to the same (S6 Fig) or different neighborhoods (S5 Fig). For example, when external and household weights were equal, it took an average of ~ 5.5 weeks to reach peak cases with mild symptoms, ~ 7 weeks until peak cases hospitalized with severe infection, and ~ 8.5 weeks to the peak of cases in critical care. 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