Epidemiological Characteristics of Imported COVID-19 Cases, March to December 2020, Chengdu, China: Implication for Quarantine and Isolation of International Travelers

Background: International flights have accelerated the global spread of Coronavirus Disease 2019 (COVID-19). Determination of the optimal quarantine period for international travelers is crucial to prevent the local spread caused by imported COVID-19 cases.Methods: We performed a retrospective epidemiological study using 491 imported COVID-19 cases in Chengdu, China, to describe the characteristic of the cases and estimate the time from arrival to confirmation for international travelers using nonparametric survival methods.Results: Among the 491 imported COVID-19 cases, 194 (39.5%) were asymptomatic infections. The mean age was 35.6 years (SD=12.1 years) and 83.3% were men. The majority (74.1%) were screened positive for SARS-CoV-2, conducted by Chengdu Customs District, the People’s Republic of China. Asymptomatic cases were younger than presymptomatic or symptomatic cases (P<0.01). The daily number of imported COVID-19 cases displayed jagged changes. 95% of COVID-19 cases were confirmed by PT-PCR within 14 days (95% CI: 13-15) after arriving in Chengdu.Conclusions: A 14-day quarantine measure can ensure non-infection among international travelers with a 95% probability. Policymakers may consider an extension of the quarantine period to minimize the negative consequences of the COVID-19 confinement and prevent the international spread of COVID-19.

Estimation of the Onset Rate and the Number of Asymptomatic Patients of COVID-19 From the Proportion of Untraceable Patients

A simple method is devised to estimate the onset rate of COVID-19 from the proportion of untraceable patients tested positive, which allows us to obtain the number of asymptomatic patients, the number of infectious patients and the effective reproduction number. The recent data in Tokyo indicate that there are about six times as many infectious patients in the city as the daily confirmed new cases. It is shown that a quarantine measure on non-symptomatic patients is critically important in controlling the pandemic.

Estimation of the onset rate and the number of asymptomatic patients of COVID-19 from the proportion of untraceable patients

A simple method is devised to estimate the onset rate of COVID-19 from the proportion of untraceable patients tested positive, which allows us to obtain the number of asymptomatic patients, the number of infectious patients and the effective reproduction number. The recent data in Tokyo indicate that there are about six times as many infectious patients in the city as the daily confirmed new cases. It is shown that a quarantine measure on non-symptomatic patients is critically important in controlling the pandemic.

Early stage nonclinical pulmonary disorder in COVID-19 may present asymptomatic and fuel the contagion

Evidence shows that pulmonary problems in coronavirus disease 2019 (COVID-19) may set off from vascular injury that progresses to physiological disturbances through a compromised gas exchange, following an infection with the severe acute respiratory syndrome coronavirus 2. In this process, inefficient gas exchange in the alveolar could precipitate silent nonclinical hypoxemia. Unfortunately, patients with “silent hypoxemia” do not necessarily experience any breathing difficulty (dyspnea) at the early stage of COVID-19 while the disease progresses. As a result, several asymptomatic, presymptomatic and patients with mild symptoms may escape quarantine measure and thus continue to spread the virus through contacts. Therefore, early diagnosis of “silent hypoxemia”, which attracts no clinical warnings, could be an important diagnostic measure to prevent acute respiratory distress syndrome from the risk of pulmonary failure among the presymptomatic and as a screening tool in the asymptomatic who are hitherto potential spreaders of the virus.

A COVID-19 Spread Model of the Discrete Grid to Assess the Potential of Non-pharmaceutical Interventions

Background: The outbreak of COVID-19 posed a serious threat to human health, economic development, and social stability worldwide, and many countries had taken different interventions to control the deterioration of the epidemic. Although many studies have evaluated the effectiveness of these interventions, there were few reasonable explanations for the practical geographic significance of the model parameters. Our aim was to evaluate the potential of different interventions to mitigate the spread of the epidemic, including discussion about the different time and intensity of implementation, and map parameters of model to the practical application meanings of the special interventions.Methods: In this study, a COVID-19 spread model based on the discrete grid was proposed from perspective of geography. A multi-level grid was introduced to describe the quarantine status and intensity in different spaces, which also combined with the model of medical reception-cured and self-protection, and the spatiotemporal evolution process of early COVID-19 spread was simulated based on the spatial correlation, finally, the effect of interventions was quantitatively analyzed by the dynamic transmission model of COVID-19.Results: Quarantine measure were the most effective interventions, which could effectively reduce the peak value of infection, advance the arrival time of the peak, and shorten the duration of the epidemic, but it only played a role under sufficient intensity; the medical reception-cured and self-protection measure could effectively fatten the infection curve and slowed the spread of the epidemic in the early stage, which could provide more buffer time for the relevant government departments, but the practical effect was not obvious because of the limitation of actually invested resources. The role of the medical reception-cured measure was more reflected in the reduction of the number of deaths, and the effect of the self-protection measure could be reduced in strict quarantine measure.Conclusions: Results of the study indicated that the quarantine, medical reception-cured and self-protection measures were effective, and mitigating the spread of COVID-19 by achieving strong interventions was necessary. Strict quarantine should be implementing as soon as possible in countries with serious development of COVID-19.

COVID- 19 Quarantine and the way forward

Quarantine is a tool that was used anciently and now used as a public health measure in a more strategic manner for containment of a disease. It requires a lot of planning for implementation depending upon the burden of disease, resources to carry out the same in a stringent manner. Benefits and outcomes need to be measured carefully while imposing quarantine especially of a larger scale. We have tried to put up the rationale behind the current quarantine measure carried out in the wake of COVID 19 and factors to keep in mind for the future.

Optimalization of Temperature to Control Araecerus fasciculatus de Geer (Coleoptera: Anthribidae) on Nutmeg

The exported nutmeg of Indonesia is frequently affected by the coffee bean weevil, Araecerus fasciculatus de Geer (Coleoptera: Anthribidae), so that it should be fumigated prior to export. CH3Br is an effective fumigant as quarantine measure for export products for 24 h, but this fumigant has been prohibited. Therefore, air temperature treatment is one of the alternative strategies. This research was aimed to determine the optimum air temperature in controlling A. fasciculatus on nutmeg. Healthy nutmeg, infected and A. fasciculatus-containing nutmeg, as well as individual adults of A. fasciculatus were treated with air temperature of 30−70°C for 1−24 h. The optimum air temperature was the lowest temperature which could kill 100% of examined insects. The results showed that 100% mortality of A. fasciculatus adults outside nutmeg occurred at air temperature of 45°C for 12 h or 50°C for 6 h. Meanwhile, 100% mortality of life stadium of A. fasciculatus inside nutmeg happened at air temperature of 55°C for 24 h. The raising of air temperature at 30−50°C for 24 h decreased the water content of nutmeg from 5.59±0.25 to 3.79±0.24%. The increment of temperature from 50 to 55°C for 24 h reduced the weight of nutmeg from 5.20±0.72 to 5.04±0.70 g. Air temperature treatment at 45−50°C for 12−24 h could eliminate adults of A. fasciculatus on exported nutmeg and air temperature of 55°C for 24 h could remove all life stadia of A. fasciculatus within nutmeg. IntisariBiji pala ekspor Indonesia sering diserang oleh kumbang bubuk biji kopi, Araecerus fasciculatus de Geer (Coleoptera: Anthribidae), sehingga harus difumigasi sebelum diekspor. Tindakan karantina pada produk ekspor yang sering menggunakan CH3Br efektif selama 24 jam, namun fumigan ini sudah dilarang. Oleh karena itu, perlakuan suhu udara merupakan salah satu alternatifnya. Penelitian ini bertujuan untuk menentukan suhu udara optimal untuk mengendalikan A. fasciculatus pada biji pala. Biji pala yang sehat, biji pala yang terserang dan berisi serangga A. fasciculatus serta imago A. fasciculatus diperlakukan dengan suhu udara 30−70°C selama 1−24 jam. Suhu udara optimal yaitu suhu terendah yang dapat membunuh 100% serangga uji. Hasil penelitian menunjukkan bahwa 100% mortalitas imago A. fasciculatus di luar biji pala terjadi pada suhu udara 45°C selama 12 jam atau 50°C selama 6 jam. Sementara itu, mortalitas 100% stadia hidup A. fasciculatus di dalam biji pala terjadi pada suhu udara 55°C selama 24 jam. Kenaikan suhu udara 30−50°C selama 24 jam menurunkan kadar air biji pala dari 5,59±0,25 menjadi 3,79±0,24%. Peningkatan suhu dari 50 menjadi 55°C selama 24 jam menurunkan berat biji pala dari 5,20±0,72 menjadi 5,04±0,70 g. Perlakuan suhu udara 45−50°C selama 12−24 jam dapat mengeliminasi imago A. fasciculatus pada biji pala ekspor dan suhu udara 55°C selama 24 jam dapat mengeliminasi semua stadia hidup A. fasciculatus di dalam biji pala.