ABSTRACT
Current explosive outbreak of COVID-19 around the world is a complex spatiotemporal process with hidden interactions between viruses and humans. This study aims at clarifying the transmission patterns and the driving mechanism that contributed to the COVID-19 epidemics across the provinces of China. Thus a new dynamical transmission model is established by ordinary differential system. The model takes into account the hidden circulation of COVID-19 virus among/within humans, which incorporates the spatial diffusion of infection by parameterizing human mobility. Theoretical analysis indicates that the basic reproduction number is a unique epidemic threshold, which can unite infectivity in each region by human mobility, and can totally determine whether COVID-19 proceeds among multiple regions. By validating the model with real epidemic data in China, it is found that (1) if without any intervention, COVID-19 would overrun China within three months, resulting in more than 1.1 billion infections; (2) high frequency of human mobility can trigger COVID-19 diffusion across each province in China, no matter where the initial infection locates; (3) travel restrictions and other non-pharmaceutical interventions must be implemented simultaneously for disease control; and (4) infection sites in central and east (rather than west and northeast) of China would easily stimulate quick diffusion of COVID-19 in the whole country.
Subject(s)
COVID-19 , Encephalitis, ArbovirusABSTRACT
The novel coronavirus disease 2019 (COVID-19) has been the biggest public health problem of the present world. As the number of people suffering from the pandemic is rising, it is likely to claim more life and worsen global health and economy. Nepal, one of the developing countries in South Asia has been strongly influenced by the pandemic and struggling to contain it with multiple interventions, however, spatiotemporal dynamics of the epidemic and its linkage with various intervention strategies has not been studied yet. Here, we employed the prospective spatial-temporal analysis with SaTScan assessing dynamics of the COVID-19 cases from 23 January to 31 August 2020 at district level in Nepal. The results revealed that COVID-19 dynamics in the early stage of transmission was slower and confined in certain districts. However, from the third week of April, transmission spread rapidly across districts of Province No. 2 and Sudoorpaschim Province, primarily introduced by Nepalese citizens returning from India. Despite nationwide lockdown, nine statistically significant active and emerging clusters were detected between 23 January and 21 July 2020, whereas ten emerging clusters were observed for extended period to 31 August. The population density and population inflow from India crossing the sealed border had significant effects on the elevated risk of the epidemic. The capital city Kathmandu has become the highest-risk active cluster since August when travel restriction has been suspended. Movement restriction appears to be the most effective non-pharmaceutical intervention against the COVID-19 for resource-scarce countries with limited health care facilities. Our findings could be valuable to the health authorities within Nepal and beyond to better allocate resources and improve interventions on the pandemic for containing it efficiently.
Subject(s)
COVID-19ABSTRACT
Background: Contact tracing with quarantine of SARS-CoV-2 positive contacts is required on an unprecedented scale worldwide.Methods: During February 1-March 25, 2020, COVID-19 cases in Hubei province were traced by more than 1800 teams. PCR positive contacts without COVID-19 symptoms with two or more consecutive positive tests for SARS-CoV-2 were categorized as: (a) asymptomatic SARS-CoV-2 if without COVID-19 symptoms throughout the > 14 days of quarantine, (b) pre-symptomatic SARS-CoV-2 if COVID-19 symptoms started during the quarantine, and (c) false positive contacts if two consecutive follow-up qRT-PCRs were negative after an initial positive SARS-CoV-2 test.Findings: 48,944 COVID-19 patients identified 277,066 contacts who were tested for SARS-CoV-2; upon ascertainment, 3,152 contacts without symptoms were SARS-CoV-2 PCR positive without symptoms, and 50 contacts were false positives. After quarantine, 2928 were classified as asymptomatic and 174 were pre-symptomatic SARS-CoV-2 contacts, with a pre-symptomatic case fatality (11/174) of 6.3%. The average interval between the initial SARS-CoV-2 PCR positive and onset of COVID-19 symptoms was 9.7 days, and the average time from onset of symptoms to death for deceased pre-symptomatic cases was 6.3 days (range = 1 - 35 days).Interpretation: Contact tracing of COVID-19 cases required many contact tracing teams, testing all contacts without COVID-19 symptoms, and quarantine of asymptomatic SARS-CoV-2 positive contacts. Countries with limited contact tracing, testing and quarantine of asymptomatic SARS-CoV-2 infected contacts under-estimate the number of infected asymptomatic SARS-CoV-2 contacts, and their contribution to COVID-19 spread.Funding Statement: National Natural Science Foundation of China (82041021), Bill & Melinda Gates Foundation (INV-006371).Declaration of Interests: The authors declare they have no conflict of interest.Ethics Approval Statement: This study was approved by the Medical Research Ethics Review Committee of Sun Yat-sen University School of Public Health (No.: 2020016). Consistent with public health regulations the informed consent was waived because data were collected as part of public health practice associated with the COVID-19 outbreak investigation and response.
Subject(s)
COVID-19ABSTRACT
The current explosive outbreak of coronavirus (COVID-19) is posing serious threats to public health and economy around the world. To clarify the coupling mechanism between this disease and economy, a new dynamical system is established. It is theoretically proved that the basic reproduction number is a nonlinear combination of parameters regarding disease transmission, intervention and economy effect, which totally determines the stability of the disease-free and endemic equilibria. Further results indicate the existence of interaction and mutual restraint among the transmission, intervention and economy, in which strong coupling of COVID-19 and economy would trigger disease outbreak and form poverty trap, while adaptive isolation of at-risk population could effectively reduce morbidity at the cost of least economic loss. Our findings can offer new insights to improve the intervention strategies against COVID-19.
Subject(s)
COVID-19ABSTRACT
Importance A large number of healthcare workers (HCWs) were infected by SARS-CoV-2 during the ongoing outbreak of COVID-19 in Wuhan, China. Hospitals are significant epicenters for the human-to-human transmission of the SARS-CoV-2 for HCWs, patients, and visitors. No data has been reported on the details of hospital environmental contamination status in the epicenter of Wuhan. Objective To investigate the extent to which SARS-CoV-2 contaminates healthcare settings, including to identify function zones of the hospital with the highest contamination levels and to identify the most contaminated objects, and personal protection equipment (PPE) in Wuhan, China. Design A field investigation was conducted to collect the surface swabs in various environments in the hospital and a laboratory experiment was conducted to examine the presence of the SARS-CoV-2 RNA. Setting Six hundred twenty-six surface samples were collected within the Zhongnan Medical Center in Wuhan, China in the mist of the COVID-19 outbreak between February 7 - February 27, 2020. Participants Dacron swabs were aseptically collected from the surfaces of 13 hospital function zones, five major objects, and three major personal protection equipment (PPE). The SARS-CoV-2 RNAs were detected by reverse transcription-PCR (RT-PCR). Main Outcomes and Measures SARS-CoV-2 RNAs Results The most contaminated zones were the intensive care unit specialized for taking care of novel coronavirus pneumonia (NCP) (31.9%), Obstetric Isolation Ward specialized for pregnant women with NCP (28.1%), and Isolation Ward for NCP (19.6%). We classified the 13 zones into four contamination levels. The most contaminated objects are self-service printers (20.0%), desktop/keyboard (16.8%), and doorknob (16.0%). Both hand sanitizer dispensers (20.3%) and gloves (15.4%) were most contaminated PPE. Conclusions and Relevance Many surfaces were contaminated with SARS-CoV-2 across the hospital in various patient care areas, commonly used objects, medical equipment, and PPE. The 13 hospital function zones were classified into four contamination levels. These findings emphasize the urgent need to ensure adequate environmental cleaning, strengthen infection prevention training, and improve infection prevention precautions among HCWs during the outbreak of COVID-19. The findings may have important implications for modifying and developing urgently needed policy to better protect healthcare workers during this ongoing pandemic of SARS-CoV-2.
Subject(s)
COVID-19 , Coronavirus InfectionsABSTRACT
The outbreak of pneumonia caused by a novel coronavirus (2019-nCoV) in Wuhan City of China obtained global concern, the population outflow from Wuhan has contributed to spatial expansion in other parts of China. We examined the effects of population outflow from Wuhan on the 2019-nCoV transmission in other provinces and cities of China, as well as the impacts of the city closure in Wuhan. We observed a significantly positive association between population movement and the number of cases. Further analysis revealed that if the city closure policy was implemented two days earlier, 1420 (95% CI: 1059, 1833) cases could be prevented, and if two days later, 1462 (95% CI: 1090, 1886) more cases would be possible. Our findings suggest that population movement might be one important trigger of the 2019-nCoV infection transmission in China, and the policy of city closure is effective to prevent the epidemic.