The patterns and driving forces of dengue invasions in China.

BACKGROUND: Global connectivity and environmental change pose continuous threats to dengue invasions from worldwide to China. However, the intrinsic relationship on introduction and outbreak risks of dengue driven by the landscape features are still unknown. This study aimed to map the patterns on source-sink relation of dengue cases and assess the driving forces for dengue invasions in China. METHODS: We identified the local and imported cases (2006-2020) and assembled the datasets on environmental conditions. The vector auto-regression model was applied to detect the cross-relations of source-sink patterns. We selected the major environmental drivers via the Boruta algorithm to assess the driving forces in dengue outbreak dynamics by applying generalized additive models. We reconstructed the internal connections among imported cases, local cases, and external environmental drivers using the structural equation modeling. RESULTS: From 2006 to 2020, 81,652 local dengue cases and 12,701 imported dengue cases in China were reported. The hotspots of dengue introductions and outbreaks were in southeast and southwest China, originating from South and Southeast Asia. Oversea-imported dengue cases, as the Granger-cause, were the initial driver of the dengue dynamic; the suitable local bio-socioecological environment is the fundamental factor for dengue epidemics. The Bio8 [odds ratio (OR) = 2.11, 95% confidence interval (CI): 1.67-2.68], Bio9 (OR = 291.62, 95% CI: 125.63-676.89), Bio15 (OR = 4.15, 95% CI: 3.30-5.24), normalized difference vegetation index in March (OR = 1.27, 95% CI: 1.06-1.51) and July (OR = 1.04, 95% CI: 1.00-1.07), and the imported cases are the major drivers of dengue local transmissions (OR = 4.79, 95% CI: 4.34-5.28). The intermediary effect of an index on population and economic development to local cases via the path of imported cases was detected in the dengue dynamic system. CONCLUSIONS: Dengue outbreaks in China are triggered by introductions of imported cases and boosted by landscape features and connectivity. Our research will contribute to developing nature-based solutions for dengue surveillance, mitigation, and control from a socio-ecological perspective based on invasion ecology theories to control and prevent future dengue invasion and localization.

Molecular epidemiological analysis of COVID-19 imported cases in Ruili from July to November, 2021

Objective To analyze the epidemiological and genomic characteristics of COVID-19 cases imported by land in Ruili, and to provide reference for border epidemic prevention and control in Yunnan Province. Methods We collected information about SARS-CoV-2 infected individuals from overseas land in Ruili, Yunnan from July to November, 2021. The epidemiological characteristics were statistically analyzed. The second-generation sequencing platform of Illumina was used to conduct high-through-put sequencing on the selected 40 positive samples and to analyze their genotyping and variation characteristics. Results During the study period,Ruili City reported 796 COVID-19 cases from abroad.The median age of COVID-19 cases was 28.5 years (Interquantile range 10, range 1–85). The gender ratio between men and women was 4.61 : 1, Most of these infected individuals engaged in business services, accounting for 49.75% (396/796) , 95.60% of COVID-19 cases were mild and moderate cases. The sequencing results of 34 cases can be divided into three clades according to Nextstrain typing method, including 24 cases belong to 21A(Delta) clade, 9 cases belong to 21I(Delta) clade and 1 case belongs to 20I (Alpha V1) clade. Conclusions The virus genotypes of the cases in this study were mainly divided into three branches and there were some differences among them, most of which were Delta mutants.We should continue to implement border control measures and continue to monitor the virus mutation of imported cases, so as to evaluate the threat of the mutant strain to the current situation of epidemic prevention and control in Yunnan Province. © 2023, Publication Centre of Anhui Medical University. All rights reserved.

Analysis of the characteristics of imported COVID-19 cases in mainland China

Objective This study aimed to examine the epidemic characteristics of the COVID-19 imported cases entering mainland China from March 4, 2020 to October 31, 2021, so as to provide the reference for the prevention and control of imported epidemic at present. Methods Data were collected from the Daily Summary on the COVID-19 epidemic issued by the national/provincial health commission official website from March 4, 2020 to October 31, 2021, including " number of imported cases and existing imported cases and source country/territory and destination province for imported cases. Joinpoint regression was used to examine the time trends in the number of imported cases over time. Results From March 4, 2020 to November 3, 2021, the number of monthly newly imported cases and existing confirmed cases changed as a " W” shape. The imported cases came from 152 counties and territories in total, mainly from Myanmar, United States, Philippines and Russia (accounting for 27.6% of all imported cases). The number of imported cases mainly entered Shanghai, Guangdong, Yunnan, Sichuan, and Fujian, explaining 70.59% of total imported cases. Conclusions The great fluctuating change of imported cases in the mainland of China may be related to the change of global COVID-19 epidemic and domestic prevention and control policies. Considering the imbalanced distribution of source country/territory and destination province of imported cases, the government should take targeted measures in important source countries/terriories and destination provinces. Each province and municipality should modify its policy for preventing the imported epidemic dynamically according to the latest characteristic of source country/territory and virus mutation. © 2023, Publication Centre of Anhui Medical University. All rights reserved.

Molecular epidemiological analysis of COVID-19 imported cases in Ruili from July to November, 2021.

Objective To analyze the epidemiological and genomic characteristics of COVID-19 cases imported by land in Ruili, and to provide reference for border epidemic prevention and control in Yunnan Province. Methods We collected information about SARS-CoV-2 infected individuals from overseas land in Ruili, Yunnan from July to November, 2021. The epidemiological characteristics were statistically analyzed. The second-generation sequencing platform of Illumina was used to conduct high-through-put sequencing on the selected 40 positive samples and to analyze their genotyping and variation characteristics. Results During the study period,Ruili City reported 796 COVID-19 cases from abroad.The median age of COVID-19 cases was 28.5 years (Interquantile range 10, range 1-85). The gender ratio between men and women was 4.61 : 1, Most of these infected individuals engaged in business services, accounting for 49.75% (396/796) , 95.60% of COVID-19 cases were mild and moderate cases. The sequencing results of 34 cases can be divided into three clades according to Nextstrain typing method, including 24 cases belong to 21A(Delta) clade, 9 cases belong to 21I(Delta) clade and 1 case belongs to 20I (Alpha V1) clade. Conclusions The virus genotypes of the cases in this study were mainly divided into three branches and there were some differences among them, most of which were Delta mutants.We should continue to implement border control measures and continue to monitor the virus mutation of imported cases, so as to evaluate the threat of the mutant strain to the current situation of epidemic prevention and control in Yunnan Province.Copyright © 2023, Publication Centre of Anhui Medical University. All rights reserved.

Analysis of the characteristics of imported COVID-19 cases in mainland China.

Objective This study aimed to examine the epidemic characteristics of the COVID-19 imported cases entering mainland China from March 4, 2020 to October 31, 2021, so as to provide the reference for the prevention and control of imported epidemic at present. Methods Data were collected from the Daily Summary on the COVID-19 epidemic issued by the national/provincial health commission official website from March 4, 2020 to October 31, 2021, including " number of imported cases and existing imported cases and source country/territory and destination province for imported cases. Joinpoint regression was used to examine the time trends in the number of imported cases over time. Results From March 4, 2020 to November 3, 2021, the number of monthly newly imported cases and existing confirmed cases changed as a " W" shape. The imported cases came from 152 counties and territories in total, mainly from Myanmar, United States, Philippines and Russia (accounting for 27.6% of all imported cases). The number of imported cases mainly entered Shanghai, Guangdong, Yunnan, Sichuan, and Fujian, explaining 70.59% of total imported cases. Conclusions The great fluctuating change of imported cases in the mainland of China may be related to the change of global COVID-19 epidemic and domestic prevention and control policies. Considering the imbalanced distribution of source country/territory and destination province of imported cases, the government should take targeted measures in important source countries/terriories and destination provinces. Each province and municipality should modify its policy for preventing the imported epidemic dynamically according to the latest characteristic of source country/territory and virus mutation.Copyright © 2023, Publication Centre of Anhui Medical University. All rights reserved.

Risk assessment of imported COVID-19 in China: A modelling study in Sichuan Province.

The importation of COVID-19 cases in China is due to the returning of Chinese citizens abroad, where the majority of cases stand. This study aimed to evaluate the risk of importing COVID-19 into the Sichuan Province of China and conduct a short-term risk prediction assessment and analysis. Data on COVID-19 cases in each country and Sichuan were collected, as well as visitors to Sichuan, population, area, and medical resources in each city in Sichuan province. According to different control strategies of entry aviation and quarantine control, we built models of epidemic transmission to estimate the risk for imported COVID-19 cases in 21 cities of Sichuan. Within 140 days of the policy change's implementation, the number of susceptible, infected, and recovered people in all cities followed the same pattern over time: (1) the number of susceptible people declined slowly at first, then accelerated to reach a stable value; (2) the number of infections gradually increased to a peak, then decreased; and (3) the number of recovered patients gradually increased to a stable value. Under the four different scenarios, there were no significant differences between the risk peaks because the social distance did not change. However, the peak time would be delayed due to the implementation of flight control and nucleic acid detection measures. The improvement of foreign epidemics (reduction of attenuation factors) all delayed the arrival of the peak risk value in Chengdu by about 20 days; however, the size of the peak value did not change significantly. The improvement of nucleic acid detection accuracy delayed the arrival of the peak risk value in Chengdu, but the size of the peak value did not change significantly. Therefore, flight control and the improvement of nucleic acid detection accuracy and overseas epidemic situations have positively affected the prevention and control of the epidemic in Sichuan.

New Surveillance Metrics for Alerting Community-Acquired Outbreaks of Emerging SARS-CoV-2 Variants Using Imported Case Data: Bayesian Markov Chain Monte Carlo Approach.

BACKGROUND: Global transmission from imported cases to domestic cluster infections is often the origin of local community-acquired outbreaks when facing emerging SARS-CoV-2 variants. OBJECTIVE: We aimed to develop new surveillance metrics for alerting emerging community-acquired outbreaks arising from new strains by monitoring the risk of small domestic cluster infections originating from few imported cases of emerging variants. METHODS: We used Taiwanese COVID-19 weekly data on imported cases, domestic cluster infections, and community-acquired outbreaks. The study period included the D614G strain in February 2020, the Alpha and Delta variants of concern (VOCs) in 2021, and the Omicron BA.1 and BA.2 VOCs in April 2022. The number of cases arising from domestic cluster infection caused by imported cases (Dci/Imc) per week was used as the SARS-CoV-2 strain-dependent surveillance metric for alerting local community-acquired outbreaks. Its upper 95% credible interval was used as the alert threshold for guiding the rapid preparedness of containment measures, including nonpharmaceutical interventions (NPIs), testing, and vaccination. The 2 metrics were estimated by using the Bayesian Monte Carlo Markov Chain method underpinning the directed acyclic graphic diagram constructed by the extra-Poisson (random-effect) regression model. The proposed model was also used to assess the most likely week lag of imported cases prior to the current week of domestic cluster infections. RESULTS: A 1-week lag of imported cases prior to the current week of domestic cluster infections was considered optimal. Both metrics of Dci/Imc and the alert threshold varied with SARS-CoV-2 variants and available containment measures. The estimates were 9.54% and 12.59%, respectively, for D614G and increased to 14.14% and 25.10%, respectively, for the Alpha VOC when only NPIs and testing were available. The corresponding figures were 10.01% and 13.32% for the Delta VOC, but reduced to 4.29% and 5.19% for the Omicron VOC when NPIs, testing, and vaccination were available. The rapid preparedness of containment measures guided by the estimated metrics accounted for the lack of community-acquired outbreaks during the D614G period, the early Alpha VOC period, the Delta VOC period, and the Omicron VOC period between BA.1 and BA.2. In contrast, community-acquired outbreaks of the Alpha VOC in mid-May 2021, Omicron BA.1 VOC in January 2022, and Omicron BA.2 VOC from April 2022 onwards, were indicative of the failure to prepare containment measures guided by the alert threshold. CONCLUSIONS: We developed new surveillance metrics for estimating the risk of domestic cluster infections with increasing imported cases and its alert threshold for community-acquired infections varying with emerging SARS-CoV-2 strains and the availability of containment measures. The use of new surveillance metrics is important in the rapid preparedness of containment measures for averting large-scale community-acquired outbreaks arising from emerging imported SARS-CoV-2 variants.

An epidemiological analysis of imported malaria in Shanghai during a COVID-19 outbreak.

BACKGROUND: The goal of this study was to understand the epidemiological characteristics of imported malaria in Shanghai specifically during the epidemic period of novel corona-virus pneumonia (COVID-19), to provide a reference for preventing the transmission of imported malaria after this disease had been previously eliminated. METHODS: The data of malaria cases reported in Shanghai from 2020 to 2021 were obtained from the China Information System for Disease Control and Prevention (CISDCP) and the Information System for Parasitic Disease Control and Prevention (ISPDCP). The characteristics of demographic and epidemiological distribution, travel-related information, diagnosis information, regions of infection acquisition and disposal information of epidemic situation were analysed with descriptive statistics. RESULTS: A total of 112 cases of malaria were reported in Shanghai from January 2020 to December 2021. There were 18 cases and 94 cases in 2020 and 2021, respectively, reaching the lowest and highest levels in the past 10 years. The incidence of malaria associated with seasons had an increasing trend (χ2 = 81.143, P < 0.05). These cases included Plasmodium falciparum (97, 86.61%), Plasmodium vivax (4, 3.57%), Plasmodium ovale (8, 7.14%) and Plasmodium malariae (3, 2.68%). The median age of patients with malaria was 38.0 years, the majority of these individuals were males (109, 97.32%), and most of them were labour personnel (93, 83.04%). Of the reported cases, 8 of these individuals (7.14%) reported experiencing malaria symptoms before their arrival in China after their stay overseas; 97 of these individuals (86.61%) reported experiencing symptoms within 14 days after their initial arrival from overseas; 15 of these individuals (13.39%) were diagnosed with 'severe malaria'; and 4 of these individuals (3.57%) were also diagnosed with COVID-19. All cases were imported from Africa, and there were no indigenous cases and deaths. CONCLUSION: Due to the impact of COVID-19, the number of imported malaria cases in Shanghai had greatly increased; however, prevention and control measures for imported malaria could be implemented to prevent re-transmission of this condition. Considering that the number of individuals returning from overseas labour is likely to increase in the next few years, it is necessary to strengthen the surveillance of imported malaria and to review the protocol for potential epidemic situations. Together, these measures could support the maintation of free-malaria status in Shanghai.

[Epidemiological characteristics of imported malaria in Zhengzhou City from 2016 to 2020].

OBJECTIVE: To analyze the epidemiological characteristics of reported imported malaria cases in Zhengzhou City from 2016 to 2020, so as to provide insights into the management of imported malaria in the city. METHODS: All data pertaining to cases with definitive diagnosis of malaria in Zhengzhou City from 2016 to 2020 were captured from the National Notifiable Disease Report System and the Information Management System for Parasitic Disease Control in China, including individual demographic data, and malaria onset, initial diagnosis and definitive diagnosis data. All data were descriptively analyzed. The duration from malaria onset to initial diagnosis, from initial diagnosis to definitive diagnosis and from onset to definitive diagnosis was compared among cases. In addition, the diagnoses of imported malaria cases in which definitive diagnosis was made were compared with the reexaminations by Zhengzhou Municipal Malaria Diagnosis Reference Laboratory. RESULTS: A total of 302 cases with definitive diagnosis of malaria were reported in Zhengzhou City from 2016 to 2020, and all were imported cases, with Plasmodium falciparum malaria as the predominant type (230 cases, 76.2%). There were 293 malaria cases imported from Africa (293 cases, 97.0%), which mainly included Nigeria (48 cases, 15.9%), Angola (40 cases, 13.2%), and the Democratic Republic of the Congo (29 cases, 9.6%). There was no obvious seasonality found in the date of malaria onset and time of reporting malaria. The ratio of male to female malaria cases was 49.3:1, and there were 103 cases (34.1%) with the current residency address in Zhengzhou City, 193 cases (63.9%) with the current residency address in other cities of Henan Province and 6 cases (2.0%) in other provinces of China. There were 271 cases (89.7%) seeking initial diagnosis in medical institutions, and the diagnostic accuracy of malaria was 56.6% (171/302) at initial diagnosis institutions. A total of 122 cases (40.4%) sought medical care on the day of malaria onset, and 252 cases (86.4%) within 3 days; however, only 22 cases (7.3%) were definitively diagnosed on the day of onset, and 162 cases (53.6%) diagnosed within 3 days. There were no significant differences between malaria cases seeking initial diagnosis at medical institutions and disease control and prevention institutions in terms of the duration from malaria onset to initial diagnosis (Z = -1.663, P > 0.05), from initial diagnosis to definitive diagnosis (Z = -0.413, P > 0.05) or from malaria onset to definitive diagnosis (Z = -0.838, P > 0.05). The median duration (interquartile range) from initial diagnosis to definitive diagnosis of malaria was 3.00 (2.00), 3.00 (6.00), 2.00 (4.00) d and 1.00 (1.00) d among cases seeking medical care at township-level and lower, county-, city- and province-level medical institutions, and the median duration from initial diagnosis to definitive diagnosis of malaria was significantly longer among cases seeking medical care at township-level and lower medical institutions than at city (Z = -3.286, P < 0.008 33) and province-level medical institutions (Z = -9.119, P < 0.008 33), while the median duration from initial diagnosis to definitive diagnosis [1.00 (3.00) d vs. 2.00 (4.00) d; Z = -4.099, P < 0.016] and from malaria onset to definitive diagnosis [3.00 (4.00) d vs. 4.00 (5.00) d; Z = -2.868, P < 0.016] among malaria cases with the current residency address in Zhengzhou City was both shorter than in other cities of Henan Province. The diagnostic accuracy was 89.1% (269/302) among malaria cases in which definitive diagnosis was made, and the accuracy of malaria reexaminations was 94.0% (284/302) in Zhengzhou Municipal Malaria Diagnosis Reference Laboratory. CONCLUSIONS: P. falciparum malaria was predominant among reported imported malaria cases in Zhengzhou City from 2016 to 2020, and these imported malaria cases were predominantly diagnosed at medical institutions; however, the diagnostic capability of malaria is poor in township-level and lower medical institutions. Strengthening the collaboration between medical institutions and disease control and prevention institutions and improving the diagnostic capability building at medical institutions are recommended to consolidate malaria elimination achivements.

The comparison of clinical characteristics between imported and native cases of COVID-19 in China

The study aimed to determine the trends in the manifestations and severity over the epidemic course of imported COVID-19 cases, with comparison to native cases. The clinical characteristics of imported and native Chinese COVID-19 cases included in the study were assessed and compared. The association was analyzed using Mann-Whitney U test for categorical variables, Kruskal-Wallis H test for continuous variables, and Spearman’s correlation test for disease severity. A total of 247 imported patients were enrolled, with an average age of 29 years, and 41.3% were female. The imported patients were younger than the native patients (29 vs 47 years) and included a lower proportion of fever (44.1%), chills (5.3%), fatigue (10.1%), leukopenia (14.6%), lymphopenia (39.3%), elevated C-reactive protein (CRP) (7.3%), elevated D-dimer (16.3%), and pneumonia (65.6%). Among patients with moderate severity, imported cases had a lower proportion of fever (44.2%), dyspnea (8.3%), and increased CRP (7.7%) than native cases. COVID-19 infection was less severe in imported cases than that in native cases, reflected by fewer clinical symptoms, fewer comorbidities, and lower overall severity.

Epidemiological characteristics of 17 imported patients infected with SARS-CoV-2 Omicron variant. / 17ä¾‹æ–°åž‹å† çŠ¶ç— æ¯’Omicronå˜å¼‚æ ªå¢ƒå¤–è¾“å ¥æ„ŸæŸ“è€ çš„æµè¡Œç— å­¦ç‰¹å¾.

OBJECTIVES: With the continuous generation of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pressure of epidemic prevention and control continues to increase in China. Omicron with stronger infectiousness, immune escape ability and repeated infection ability spread to many countries and regions around the world in a short period of time. China has also successively reported cases of imported Omicron infections. This study aims to understand the epidemiological characteristics of Omicron variant via analyzing the epidemiological characteristics of imported patients with Omicron in Hunan Province, and to provide reference for preventing and controlling the imported epidemics. METHODS: The clinical data of imported patients with coronavirus disease 2019 admitted to Hunan Province from December 16 to December 31, 2021 were retrospectively collected. The epidemiological information, general information, clinical classification, clinical symptoms, vaccination status, and lung CT were analyzed. Nasopharyngeal swabs and blood samples were collected. Virus nucleic acid was detected by magnetic beads method using SARS-CoV-2 detection kit. Ct values of ORF1ab gene and N gene were compared between asymptomatic infected patients and confirmed patients. The specific IgM and IgG antibodies were detected by chemiluminescence assay using SARS-CoV-2 IgM test kit and SARS-CoV-2 IgG test kit, respectively. Ct values of IgM and IgG antibodies were compared between asymptomatic infected patients and confirmed patients. RESULTS: Seventeen patients with Omicron variant infection were treated in Hunan, including 15 confirmed patients (5 common type and 10 mild type) and 2 asymptomatic infection patients. The 17 patients were all Chinese, they were generally young, and 16 were male. There were 9 patients with diseases. Of them 3 patients had respiratory diseases. All 17 patients had completed the whole process of vaccination, but only one person received a booster shot of SARS-CoV-2 vaccine. The clinical manifestations of the patients were mild, mainly including dry/painful/itchy throat, cough, and fatigue. The total protein and creatine in the asymptomatic infection and confirmed cases infected with Omicron variant were all within the normal range, but other biochemical indicators were abnormal. There were the significant differences in C-reactive protein and fibrinogen between asymptomatic infection and confirmed patients (both P<0.05). There were more patients with elevated C-reactive protein in confirmed patients than without confirmed ones. The detection rate of specific IgM and IgG antibodies on admission was 100%, and there was no significant difference in the specific antibody levels between asymptomatic infection and confirmed patients (P>0.05). There were no significant differences in Ct values of ORF1ab gene and N gene (21.35 and 18.39 vs 19.22 and 15.67) between the asymptomatic infection and the confirmed patients (both P>0.05). Only 3 patients had abnormal lung CT, showing a small amount of patchy and cord-like shadows. One of them had no abnormality on admission but had pulmonary lesions and migratory phenomenon after admission. CONCLUSIONS: The patients with Omicron variant tend to be young people and have milder clinical symptoms, but the viral load is high and the infectiveness is strong. Therefore, the timely identification and effective isolation and control for asymptomatic infections and confirmed patients with mild symptoms are extremely important. In terms of epidemic prevention and control, the government still needs to strengthen the risk control of overseas input, adhere to normalized epidemic prevention and control measures, to effectively control the source of infection, cut off the route of transmission, and protect vulnerable people.

Genomic analysis of early transmissibility assessment of the D614G mutant strain of SARS-CoV-2 in travelers returning to Taiwan from the United States of America.

BACKGROUND: There is a global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Information on viral genomics is crucial for understanding global dispersion and for providing insight into viral pathogenicity and transmission. Here, we characterized the SARS-CoV-2 genomes isolated from five travelers who returned to Taiwan from the United States of America (USA) between March and April 2020. METHODS: Haplotype network analysis was performed using genome-wide single-nucleotide variations to trace potential infection routes. To determine the genetic variations and evolutionary trajectory of the isolates, the genomes of isolates were compared to those of global virus strains from GISAID. Pharyngeal specimens were confirmed to be SARS-CoV-2-positive by RT-PCR. Direct whole-genome sequencing was performed, and viral assemblies were subsequently uploaded to GISAID. Comparative genome sequence and single-nucleotide variation analyses were performed. RESULTS: The D614G mutation was identified in imported cases, which separated into two clusters related to viruses originally detected in the USA. Our findings highlight the risk of spreading SARS-CoV-2 variants through air travel and the need for continued genomic tracing for the epidemiological investigation and surveillance of SARS-CoV-2 using viral genomic data. CONCLUSIONS: Continuous genomic surveillance is warranted to trace virus circulation and evolution in different global settings during future outbreaks.

Impact of travel ban implementation on COVID-19 spread in Singapore, Taiwan, Hong Kong and South Korea during the early phase of the pandemic: a comparative study.

BACKGROUND: The COVID-19 pandemic has elicited imposition of some form of travel restrictions by almost all countries in the world. Most restrictions currently persist, although some have been gradually eased. It remains unclear if the trade-off from the unprecedented disruption to air travel was well worth for pandemic containment. METHOD: A comparative analysis was conducted on Singapore, Taiwan, Hong Kong and South Korea's COVID-19 response. Data on COVID-19 cases, travel-related and community interventions, socio-economic profile were consolidated. Trends on imported and local cases were analyzed using computations of moving averages, rate of change, particularly in response to distinct waves of travel-related interventions due to the outbreak in China, South Korea, Iran & Italy, and Europe. RESULTS: South Korea's travel restrictions were observed to be consistently more lagged in terms of timeliness and magnitude, with their first wave of travel restrictions on flights departing from China implemented 34 days after the outbreak in Wuhan, compared to 22-26 days taken by Singapore, Taiwan and Hong Kong. South Korea's restrictions against all countries came after 91 days, compared to 78-80 days for the other three countries. The rate of change of imported cases fell by 1.08-1.43 across all four countries following the first wave of travel restrictions on departures from China, and by 0.22-0.52 in all countries except South Korea in the fifth wave against all international travellers. Delayed rate of change of local cases resulting from travel restrictions imposed by the four countries with intrinsic importation risk, were not observed. CONCLUSIONS: Travel restriction was effective in preventing COVID-19 case importation in early outbreak phase, but may still be limited in preventing general local transmission. The impact of travel restrictions, regardless of promptness, in containing epidemics likely also depends on the effectiveness of local surveillance and non-pharmaceutical interventions concurrently implemented.

Challenges Caused by Imported Cases Abroad for the Prevention and Control of COVID-19 in China.

Background: Overseas imported cases of COVID-19 continue to increase in China, so we conducted this study to review the epidemiological characteristics of these patients. Methods: From February 26 to April 4, 2020, the imported cases from abroad were enrolled in this study. The effect of prevention countermeasures in curbing the spread of COVID-19 was assessed in this study. Moreover, we defined incubation period and confirmed time as from the date of leaving the epicenter to date of symptom onset and date of final diagnosed, respectively, and the interval of symptom onset to final diagnosed time was defined as diagnostic time. Categorical variables were summarized as numbers and percentages, and the difference among the variables were analyzed. Results: For 670 cases imported from abroad, 555 were Chinese and 115 were foreigners. Apparently, confirmed cases had significantly decreased after China was compelled to temporarily suspend the entry of foreign passport holders with valid visas or residence permits; 6 days after implement of controlled measures, the daily new confirmed cases were reduced to 13 cases. Moreover, about 84.3% of patients (166/197) presented symptoms 1 week after leaving the epicenter, and notably seven patients (3.6%) had symptoms 2 weeks after leaving the epicenter. The median incubation period was 3.0 days (inter quartile range, 1.0 to 6.0), the 95th percentile was 11.6 days. Additionally, most of cases (92.9%) were detected positively of nucleic acid after symptom onset with 4 days, the median diagnostic time was 2.0 days (interquartile range, 1.0 to 3.0), and the 95th percentile of the distribution was 5.0 days. Finally, about 5.8% of patients were healthy carriers, and the median confirmed time of asymptomatic patients was 4.0 days (interquartile range, 2.0 to 9.0). The following variables might be associated with confirmed time: symptom type (P = 0.005), exported regions (P < 0.001), and symptom onset time (P < 0.001). Conclusions: The prevention countermeasures for imported cases implemented by the Chinese government played an indispensable role in curbing the spread of COVID-19; the time of departure from epicenter could provide an estimate of the incubation period; and a confirmed time, 2-week quarantine period might need to be prolonged, while asymptomatic patients should be closely monitored.

Epidemiological and clinical characteristics of imported cases of COVID-19: a multicenter study.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic continues to expand. Herein, we report the epidemiological and clinical features of 478 patients with confirmed COVID-19 from a multicenter study conducted in four cities in China excluding Wuhan. METHODS: A total of 478 patients transferred by emergency medical services to designated hospitals in four major cities in China (Beijing, Chongqing, Jinan, and Nanning) were enrolled. We compared the characteristics of imported and indigenous cases and calculated the frequencies of fatal, severe, mild, and asymptomatic disease. The results were used to generate a pyramid of COVID-19 severity. RESULTS: The mean age of patients with COVID-19 was 46.9 years and 49.8% were male. The most common symptoms at onset were fever (69.7%), cough (47.5%), fatigue (24.5%), dyspnea (8.4%), and headache (7.9%). Most cases (313, 65.5%) were indigenous, while 165 (34.5%) were imported. Imported cases dominated during the early stages of the pandemic, but decreased from 1 February 2020 as indigenous cases rose sharply. Compared with indigenous cases, imported cases differed significantly in terms of sex (P = 0.002), severity of disease (P = 0.006), occurrence of fever (P < 0.001), family clustering (P < 0.001), history of contact (P < 0.001), and primary outcome (P < 0.001). CONCLUSIONS: Within the population studied, imported cases had distinct characteristics from those of indigenous cases, with lower fatality rates and higher discharge rates. New infections shifted from imported cases to local infection gradually, and overall infections have declined to a low level. We suggest that preventing import of cases and controlling spread within local areas can help prevent SARS-CoV-2 infection spread.

[Epidemiological characteristics of imported COVID-19 cases in Guangzhou].

Objective: To understand the epidemiological characteristics of imported COVID-19 cases in Guangzhou and provide scientific basis for the prevention and control of the disease. Methods: The data of imported COVID-19 in Guangzhou reported as of April 1, 2020 were collected from National Notifiable Disease Report System of China. The software Excel 2010 and SPSS 19.0 were applied for data cleaning and statistical analysis. Results: As of April 1, 2020, a total of 103 imported COVID-19 cases had been reported in Guangzhou, in which 92 were confirmed cases and 11 were asymptomatic infection cases. The number of the confirmed imported cases accounted for 11.4% (92/806) in of the total in China at the same time. The male to female ratio of the cases was 1.58∶1 (63∶40). The median age of the cases was 31 years (P(25)-P(75):22-40 years), range of age was 11-63 years. The main occupational distributions of the cases were business services (41/103, 39.8%) and students (36/103, 35.0%). The imported cases whose destinations were 19 provinces and municipalities rather than Guangdong after entering the country accounted for 43.7%. The main source countries of infections were the United Kingdom (27/103, 26.2%), the Philippines (13/103, 12.6%), the United States (13/103, 12.6%) and Nigeria (7/103, 6.8%). There were 34 inbound flights from which the imported COVID-19 cases were detected, in which 10 flights (10/34, 29.4%) were found to carry more than 3 cases, with an average voyage time of (11.14±0.53) hours. A total of 29 imported cases(28.2%) showed symptoms before entering the country, and 65 cases (63.1%) had been isolated before the onset of the disease. The mean free activity time of the isolated cases after the onset was (6.76±0.79) days. The average number of the imported cases' close contacts was 53. There were 13 clusters of COVID-19 caused by the imported cases, involving 36 cases (including 1 imported associated case). Conclusions: The sources of the imported COVID-19 cases in Guangzhou were widely distributed, and no cases had been found to be infected on the flights. In the early stage of the imported epidemic, there was high risk for the spread of the epidemic. Strengthened prevention and control of imported COVID-19 effectively reduced the of transmission risk of COVID-19 in communities.

Measuring imported case risk of COVID-19 from inbound international flights --- A case study on China.

With COVID-19 spreading around the world, many countries are exposed to the imported case risk from inbound international flights. Several governments issued restrictions on inbound flights to mitigate such risk. But with the pandemic controlled in many countries, some decide to reopen the economy by relaxing the international air travel bans. As the virus has still been prevailing in many regions, this relaxation raises the alarm to import overseas cases and results in the revival of local pandemic. This study proposes a risk index to measure one country's imported case risk from inbound international flights. The index combines both daily dynamic international air connectivity data and the updated global COVID-19 data. It can measure the risk at the country, province and even specific route level. The proposed index was applied to China, which is the first country to experience and control COVID-19 pandemic while later becoming exposed to high imported case risk after the epidemic centers switched to Europe and the US afterward. The calculated risk indexes for each Chinese province or region show both spatial and temporal patterns from January to April 2020. It is found that China's strict restriction on inbound flights since March 26 was very effective to cut the imported case risk by half than doing nothing. But the overall index level kept rising because of the deteriorating pandemic conditions around the world. Hong Kong and Taiwan are the regions facing the highest imported case risk due to their superior international air connectivity and looser restriction on inbound flights. Shandong Province had the highest risk in February and early March due to its well-developed air connectivity with South Korea and Japan when the pandemic peaked in these two countries. Since mid-March, the imported case risk from Europe and the US dramatically increased. Last, we discuss policy implications for the relevant stakeholders to use our index to dynamically adjust the international air travel restrictions. This risk index can also be applied to other contexts and countries to relax restrictions on particular low-risk routes while still restricting the high-risk ones. This would balance the essential air travels need and the requirement to minimize the imported case risk.

SARS-CoV-2 Genome Analysis of Japanese Travelers in Nile River Cruise.

Japan has reported 26 cases of coronavirus disease 2019 (COVID-19) linked to cruise tours on the River Nile in Egypt between March 5 and 15, 2020. Here, we characterized the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genome of isolates from 10 travelers who returned from Egypt and from patients possibly associated with these travelers. We performed haplotype network analysis of SARS-CoV-2 isolates using genome-wide single-nucleotide variations. Our analysis identified two potential Egypt-related clusters from these imported cases, and these clusters were related to globally detected viruses in different countries.

Coronavirus outbreak in Nigeria: Burden and socio-medical response during the first 100 days.

BACKGROUND: The coronavirus disease of 2019 (COVID-19) pandemic shocked the world, overwhelming the health systems of even high-income countries. Predictably, the situation has elicited social and medical responses from the public and governments, respectively. Nigeria recorded an imported case from Italy on February 27, 2020. Hence, this paper assesses the early socio-medical response to COVID-19 in Nigeria in the first 100 days after the index case. The paper employs analytical methods and collates data from various media reports and official sources. FINDINGS: The incidence of COVID-19 grew steadily in Nigeria, moving from an imported case and elitist pattern to community transmission. The case fatality stood at 2.8%. The country recorded an upsurge (52% of total cases) in the transmission of COVID-19 during the short period the lockdown was relaxed. This paper presents a concise response framework to highlight some specific multisectoral responses to the pandemic. A combination of social and medical responses to a large extent helped Nigeria curtail the spread of the virus. CONCLUSION: The potential of overwhelming COVID-19 is still imminent in Nigeria as the country is attempting to hurriedly open the economy, which could sacrifice public health gains for temporary economic gains.