key: cord-310762-3clh1zv6 authors: Azanza Ricardo, C. L.; Hernandez Vargas, E. A. title: The Risk of Lifting COVID-19 Confinement in Mexico date: 2020-06-02 journal: nan DOI: 10.1101/2020.05.28.20115063 sha: doc_id: 310762 cord_uid: 3clh1zv6 The novel coronavirus SARS-CoV-2 has paralysed our societies, leading to self isolation and quarantine for several days. As the 10th most populated country in the world, Mexico is on a major threat by COVID-19 due to the limitations of intensive care capacities, and a total of about 1.5 hospital beds for every 1000 citizens. In this paper, we projected different scenarios to evaluate sharp or gradual quarantine lifting strategies, however, even in the hypothetical scenario that Mexico would continue with full confinement, hospitals would be reaching the maximum capacity of hospital bed occupancy. Mexican government is planning to relax the strict social distancing regulations on 1 June 2020, however, epidemic rebound risks are latent. Our results suggest that lifting social confinement needs to be gradually sparse while maintaining a decentralized region strategy among the Mexican states. To substantially lower the number of infections, predictions highlight that the elderly should remain in social confinement (approximately 11.3% of the population); the confined working class (roughly 27% of the population) must gradually return in at least four parts in consecutive months; and to the last the return of students to schools (about 21.7%). As the epidemic progresses, de-confinement strategies need to be continuously re-adjusting with the new pandemic data. Assuming the most optimistic scenario by our predictions, the smallest number of new COVID-19 cases, Mexico would require at least a 3 fold increase in hospital capacities dedicated for COVID-19. Furthermore, to observe the real dimension of the epidemic, Mexico would need to increase to at least 18 samples per 1000 people, currently is only 0.6 per 1000. All mathematical models, including ours, are only a possibility of many of the future, however, the different scenarios that were developed here highlight that a gradual decentralized region de-confinement with a significant increase in healthcare capacities is paramount to avoid a high death toll in Mexico. which is the peak infection phase, the central problem of pandemic surveillance is not to monitor the growth of In this work, we fit a derivation of the SEIR model for COVID-19 14 using data of the COVID-19 epidemic 30 in Mexico 12 as well as its public health capacities and demographic conditions 11 . Different lifting confinement 31 scenarios are evaluated for the main regions of Mexico in order to inform public makers to tailor decentralized region 32 strategies through the Mexican territory with the ultimate goal to minimize deaths. 33 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 2, 2020. The susceptible population is represented by S, from which the total country population (N) is about 127 38 million 11 . The exposed population to the virus is considered by E. In the sentinel model applied in Mexico, testing 39 is about 10% of the suspected cases while 100% of hospitalized cases and deaths. The infected cases (I) once 40 reported by the Mexican Government are in a hospital or at home under confinement. Therefore, it is a reasonable 41 assumption to consider that new infections are mainly driven by the exposed population with the term β SE N . The 42 asymptomatic phase has been reported on average 5-6 days, but it can be up to 14 days 1, 3 . The exposed population 43 will leave this compartment with a rate η. A fraction ε of the exposed population that will present severe symptoms 44 or complications, and consequently counted in the reports of infected cases (I). This is approximately 20% 1, 3, 15 , 45 that is ε = 0.2. The other fraction 1 − ε will move to the compartment of remove (R), those cases that recover or die. The average infection time is about 3-7 days 16 , while the clinical recovery is 2-6 weeks after symptoms 17, 18 . Thus, we assume the recovery rate of infected cases (δ ) in 10 days. The first confirmed case of COVID-19 in Mexico was reported on February 28th, 2020 12 . At the day of social 49 confinement, 15 March 2020, the number of infected cases (I 0 ) for the whole country were 12 12 . Due to the change 50 in social movement as well as the very low number of infected cases between the first confirmed case till the day of 51 social confinement, we perform our parameter fitting at the first day of social confinement. The initial number of 52 exposed population (E 0 ) is approximately a factor f of 8 to 12 respect to the confirmed cases 19 , that approximates The compartment C is the confined population which entered with a rate q from the susceptible population. τ the 55 effect of population de-confinement, which can be attributed to government policies as well as resistant/forgetting 56 factor by the population to keep adequately the confinement. Estimations by the COVID-19 community mobility 57 report of Google 20 suggest a reduction in the mobility of about 50 to 70%. Thus, the ratio between τ/q = 2/3 would 58 represent the 60% confinement percent in the steady state. If we consider a fast confinement rate, then q = 1. 3 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 2, 2020. . A re-sampling strategy was employed to fit the parameters β and η. The range of parameter values in Table 1 60 served to generate 3000 sets of random parameters with specific statistical distributions as presented in Figure Table 1 . the reported number of infected cases, Figure 2 presents Assuming the percents of required hospital beds respect to the reported infected cases are consistent in the future 80 (about 38% for the whole country, see Figure 2 and Table A .2), the most optimistic peak of the pandemic presented 81 in Figure 1 could be about 254,174 infected cases, which would result in a saturation of hospitals. That is, the 82 whole country would require to have about 97,180 hospital beds, while the number available of beds for COVID-19 83 pandemic reported for the whole country is about 49,083 24 . This is a major public concern as Mexico would only 84 be able to provide approximately 50% for the peak of COVID-19 pandemic, otherwise hospitals capacities for 85 non-COVID-19 patients would be reduced. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 2, 2020. Considering that the confinement in Mexico was about 60% of the population 20 , we evaluate a step-wise social 93 confinement lifting based on a gradual de-confinementof different age groups. Based on Mexican reports by the 94 6 All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted June 2, 2020. . https://doi.org/10.1101/2020.05.28.20115063 doi: medRxiv preprint (approximately 42.94% of the population), G 2 are those between 25-59 years old (approximately 45.75% of the In the same spirit of the epic phrase by Goerge E.P. Box that "All models are wrong, but some are useful", our 145 model as well as others for COVID-19 has several limitations. In particular, mathematical models that are fitted 146 during the emerging phase, exponential growth, of an outbreak that have potential sources of bias 26 . Furthermore, 147 the data of infected cases in Mexico is very limited because of application of the sentinel model. While sampling is 148 based on 10% of the suspected cases while 100% of hospitalized cases and deaths, mass testing for stage 2 and 3 is 149 considered irrelevant. In fact, reports by the OECD (COVID-19) 27 underlines that Mexico is only testing 0.6-0.8 per 150 every thousand, occupying in this way Mexico the last place among countries with high number of infected cases. With 5,623 new tests on 4 May 2020, Mexico reported the highest number of samples per day 27 . Therefore, with this 152 sample rate Mexico will be unable to register the dimension of the epidemic, actually, it is expected that Mexico will 153 have a flat region as soon as the number of infected cases per day passes over 7,560. In reality, during the peak of the 154 pandemic Mexico would need to test at least 18 per every thousand to provide a better vision of the problem. With the progressing of information of COVID-19 pandemic as well as new data of infected cases in Mexico, 156 our predictions would be more accurate and hopefully less drastic scenarios. Nevertheless, our predictions underline CDC. Coronavirus diseases (COVID-2019) situation reports A Close Look at the Frontrunning Coronavirus Vaccines As of May 1 (updated) | In the Pipeline Estimates of the severity of coronavirus disease 2019 : a model-based analysis Virological assessment of hospitalized patients with COVID-2019. Nature 1-10 WHO Director-General's opening remarks at the media briefing on COVID-19 -24 Intensive care management of coronavirus disease 2019 (COVID-19): challenges and recommen-196 dations de Abril 2020). Versión estenográfica Informe diario sobre coronavirus COVID-19 en México COVID-19 Community Mobility Reports Differential Evolution -A simple and efficient adaptive scheme for global optimization 201 over continuous spaces PDEparams: parameter fitting toolbox for partial differential 203 equations in python Datos Abiertos para COVID-19 -Dirección General de Epidemiología | 205 Secretaría de Salud | Gobierno | gob Capacidad instalada en México para enfrentar al coronavirus COVID-19 Ending diabetes in Mexico Estimation in emerging epidemics: biases and remedies Testing for COVID-19 : A way to lift confinement restrictions CLAR performed the simulations. EAHV envisaged the project . All the authors discussed and wrote the paper