Modeling the effect of imported malaria on the elimination programme in KwaZulu-Natal province of South Africa.

Introduction: with imported malaria cases in a given population, the question arises as to what extent the local cases are a consequence of the imports or not. We perform a modeling analysis for a specific area, in a region aspiring for malaria-free status. Methods: data on malaria cases over ten years is subjected to a compartmental model which is assumed to be operating close to the equilibrium state. Two of the parameters of the model are fitted to the decadal data. The other parameters in the model are sourced from the literature. The model is utilized to simulate the malaria prevalence with or without imported cases. Results: in any given year the annual average of 460 imported cases, resulted in an end-of-year season malaria prevalence of 257 local active infectious cases, whereas without the imports the malaria prevalence at the end of the season would have been fewer than 10 active infectious cases. We calculate the numerical value of the basic reproduction number for the model, which reveals the extent to which the disease is being eliminated from the population or not. Conclusion: without the imported cases, over the ten seasons of malaria, 2008-2018, the KwaZulu-Natal province would have been malaria-free over at least the last 7 years of the decade indicated. This simple methodology works well even in situations where data is limited.

Modeling the Regional Distribution of International Travelers in Spain to Estimate Imported Cases of Dengue and Malaria: Statistical Inference and Validation Study.

BACKGROUND: Understanding the patterns of disease importation through international travel is paramount for effective public health interventions and global disease surveillance. While global airline network data have been used to assist in outbreak prevention and effective preparedness, accurately estimating how these imported cases disseminate locally in receiving countries remains a challenge. OBJECTIVE: This study aimed to describe and understand the regional distribution of imported cases of dengue and malaria upon arrival in Spain via air travel. METHODS: We have proposed a method to describe the regional distribution of imported cases of dengue and malaria based on the computation of the "travelers' index" from readily available socioeconomic data. We combined indicators representing the main drivers for international travel, including tourism, economy, and visits to friends and relatives, to measure the relative appeal of each region in the importing country for travelers. We validated the resulting estimates by comparing them with the reported cases of malaria and dengue in Spain from 2015 to 2019. We also assessed which motivation provided more accurate estimates for imported cases of both diseases. RESULTS: The estimates provided by the best fitted model showed high correlation with notified cases of malaria (0.94) and dengue (0.87), with economic motivation being the most relevant for imported cases of malaria and visits to friends and relatives being the most relevant for imported cases of dengue. CONCLUSIONS: Factual descriptions of the local movement of international travelers may substantially enhance the design of cost-effective prevention policies and control strategies, and essentially contribute to decision-support systems. Our approach contributes in this direction by providing a reliable estimate of the number of imported cases of nonendemic diseases, which could be generalized to other applications. Realistic risk assessments will be obtained by combining this regional predictor with the observed local distribution of vectors.

Imported infectious diseases in migrants from Latin America: A retrospective study from a referral centre for tropical diseases in Spain, 2017-2022.

INTRODUCTION: Detecting imported diseases by migrants and individuals visiting friends and relatives (VFR) is key in the prevention and management of emergent infectious diseases acquired abroad. METHODS: Retrospective descriptive study on migrants and VFR from Central and South America between 2017 and 2022 attended at a National Referral Centre for Tropical Diseases in Madrid, Spain. Demographic characteristics, syndromes and confirmed travel-related diagnoses were obtained from hospital patient medical records. RESULTS: 1654 cases were registered, median age of 42 years, 69.1% were female, and 55.2% were migrants. Most cases came from Bolivia (49.6%), followed by Ecuador (12.9%). Health screening while asymptomatic (31.6%) was the main reason for consultation, followed by Chagas disease follow-up (31%). Of those asymptomatic at screening, 47,2% were finally diagnosed of any disease, mainly Chagas disease (19,7%) and strongyloidiasis (10,2%) CONCLUSION: Our study emphasizes the importance of proactive health screening to detect asymptomatic conditions in migrants and VFR, enabling timely intervention and improved health outcomes. By understanding the unique health profiles of immigrant populations, targeted public health interventions can be devised to safeguard the well-being of these vulnerable groups.

[Epidemic status of imported malaria before and after malaria elimination in Jiaozuo City of Henan Province].

OBJECTIVE: To analyze and compare the epidemiological characteristics of imported malaria in Jiaozuo City before and after malaria elimination, so as to provide insights into the malaria surveillance during the post-elimination stage and prevention of re-establishment of imported malaria. METHODS: Data pertaining to the epidemic situation and individual investigation of malaria in Jiaozuo City before (from 2010 to 2016) and after malaria elimination (from 2017 to November, 2020) were captured from the National Notifiable Disease Reporting System and the Information System for Parasitic Diseases Control and Prevention of Chinese Center for Disease Control and Prevention and were analyzed statistically. RESULTS: A total of 74 imported malaria cases were reported in Jiaozuo City from 2010 to 2021. Imported cases were predominantly Plasmodium falciparum malaria cases in Jiaozuo City before and after malaria elimination, and there was no significant difference in the proportion of malaria parasite species (χ2 = 0.234, P > 0.05). The imported malaria cases was predominantly reported in Wuzhi County, and was identified in overseas male farmers and businessmen at ages of 20 to 59 years, while the greatest number of imported malaria cases was reported in June and December before and after malaria elimination. The imported malaria cases predominantly acquired malaria parasite infections in sub-Saharan African countries; however, the proportion of imported malaria cases returning from Southeast Asian counties increased after malaria elimination than before malaria elimination (χ2 = 5.989, P < 0.05). The longest duration from onset to definitive diagnosis of malaria reduced from 27 days before malaria elimination to 18 days after malaria elimination, and the median duration reduced from 3 days to 2 days, while the proportion of definitive diagnosis of malaria increased from 60.47% before malaria elimination to 83.87% after malaria elimination (χ2 = 4.724, P < 0.05). In addition, the proportion of malaria cases definitively diagnosed and reported by medical institutions increased after malaria elimination than before malaria elimination (χ2 = 5.406, P < 0.05). CONCLUSIONS: The imported malaria patients were predominantly P. falciparum malaria cases in Jiaozuo City during 2010 to 2021, and the patient's medical care-seeking awareness and medical staff's diagnosis and treatment ability have improved after malaria elimination. It is necessary to strengthen and improve malaria surveillance and response system and prevent the re-establishment of overseas imported malaria.

Imported Infectious Diseases, Tropical Diseases and Local Endemic Infectious Diseases in Japan.

We aimed to describe the historical perspectives and the current epidemiology of tropical, imported and local endemic infectious diseases in Japan in this review. Public health legislation for infectious diseases and immigration statistics were overviewed to provide the background of the infectious disease situation in Japan. Many tropical diseases were successfully controlled and eliminated in the latter half of the 20th century and the majority of those diseases are imported today. The trend of the main 15 imported infectious diseases before the advent of COVID-19 was summarized as well as local endemic infectious diseases in Japan. Transmission risks of traditional cuisines, lifestyles and nature exposures in Japan are introduced to guide clinicians for travel advice to prevent those local infectious diseases.

Genomic assessment of quarantine measures to prevent SARS-CoV-2 importation and transmission.

Mitigation of SARS-CoV-2 transmission from international travel is a priority. We evaluated the effectiveness of travellers being required to quarantine for 14-days on return to England in Summer 2020. We identified 4,207 travel-related SARS-CoV-2 cases and their contacts, and identified 827 associated SARS-CoV-2 genomes. Overall, quarantine was associated with a lower rate of contacts, and the impact of quarantine was greatest in the 16-20 age-group. 186 SARS-CoV-2 genomes were sufficiently unique to identify travel-related clusters. Fewer genomically-linked cases were observed for index cases who returned from countries with quarantine requirement compared to countries with no quarantine requirement. This difference was explained by fewer importation events per identified genome for these cases, as opposed to fewer onward contacts per case. Overall, our study demonstrates that a 14-day quarantine period reduces, but does not completely eliminate, the onward transmission of imported cases, mainly by dissuading travel to countries with a quarantine requirement.

Epidemiological profile of imported malaria cases in the prevention of reestablishment phase in Sri Lanka.

Sri Lanka reported the last case of indigenous malaria in October 2012, and received malaria-free certification from WHO in September 2016. Malaria cases have since, shifted from indigenous to imported, and the country remains receptive and vulnerable to malaria. A case-based epidemiological study was conducted on all imported malaria cases reported in the country in 2015 and 2016 with the aim of profiling imported malaria to improve the effectiveness of the surveillance and case management system for malaria. Data were obtained from case reports of the Anti Malaria Campaign, hospital records and laboratory registers. Over the 2 years, 77 imported malaria infections were diagnosed in 54 Sri Lankans and 23 foreign nationals. A majority of the infections were reported among males (93%) in the age group of 21-50 years (85.8%), and all were recent travelers overseas. Most patients were detected by passive case detection, but 10% of cases were detected by Active Case Detection. Only 25% of patients were diagnosed within 3 days of the onset of symptoms. In 32% of patients, the diagnosis was delayed by more than 10 days after the onset of symptoms. Plasmodium falciparum infections manifested significantly earlier after arrival in Sri Lanka than did P.vivax infections. The majority of patients (74%) were diagnosed in the Western Province, which was not endemic for malaria. A third of patients were diagnosed in the private sector. The shift in the epidemiology of malaria infection from before to after elimination has implications for preventing the reestablishment of malaria.

Rapid establishment of a frontline field laboratory in response to an imported outbreak of Ebola virus disease in western Uganda, June 2019.

The Democratic Republic of the Congo (DRC) declared an Ebola virus disease (EVD) outbreak in North Kivu in August 2018. By June 2019, the outbreak had spread to 26 health zones in northeastern DRC, causing >2,000 reported cases and >1,000 deaths. On June 10, 2019, three members of a Congolese family with EVD-like symptoms traveled to western Uganda's Kasese District to seek medical care. Shortly thereafter, the Viral Hemorrhagic Fever Surveillance and Laboratory Program (VHF program) at the Uganda Virus Research Institute (UVRI) confirmed that all three patients had EVD. The Ugandan Ministry of Health declared an outbreak of EVD in Uganda's Kasese District, notified the World Health Organization, and initiated a rapid response to contain the outbreak. As part of this response, UVRI and the United States Centers for Disease Control and Prevention, with the support of Uganda's Public Health Emergency Operations Center, the Kasese District Health Team, the Superintendent of Bwera General Hospital, the United States Department of Defense's Makerere University Walter Reed Project, and the United States Mission to Kampala's Global Health Security Technical Working Group, jointly established an Ebola Field Laboratory in Kasese District at Bwera General Hospital, proximal to an Ebola Treatment Unit (ETU). The laboratory consisted of a rapid containment kit for viral inactivation of patient specimens and a GeneXpert Instrument for performing Xpert Ebola assays. Laboratory staff tested 76 specimens from alert and suspect cases of EVD; the majority were admitted to the ETU (89.3%) and reported recent travel to the DRC (58.9%). Although no EVD cases were detected by the field laboratory, it played an important role in patient management and epidemiological surveillance by providing diagnostic results in <3 hours. The integration of the field laboratory into Uganda's National VHF Program also enabled patient specimens to be referred to Entebbe for confirmatory EBOV testing and testing for other hemorrhagic fever viruses that circulate in Uganda.

Quantifying COVID-19 importation risk in a dynamic network of domestic cities and international countries.

Since its outbreak in December 2019, the novel coronavirus 2019 (COVID-19) has spread to 191 countries and caused millions of deaths. Many countries have experienced multiple epidemic waves and faced containment pressures from both domestic and international transmission. In this study, we conduct a multiscale geographic analysis of the spread of COVID-19 in a policy-influenced dynamic network to quantify COVID-19 importation risk under different policy scenarios using evidence from China. Our spatial dynamic panel data (SDPD) model explicitly distinguishes the effects of travel flows from the effects of transmissibility within cities, across cities, and across national borders. We find that within-city transmission was the dominant transmission mechanism in China at the beginning of the outbreak and that all domestic transmission mechanisms were muted or significantly weakened before importation posed a threat. We identify effective containment policies by matching the change points of domestic and importation transmissibility parameters to the timing of various interventions. Our simulations suggest that importation risk is limited when domestic transmission is under control, but that cumulative cases would have been almost 13 times higher if domestic transmissibility had resurged to its precontainment level after importation and 32 times higher if domestic transmissibility had remained at its precontainment level since the outbreak. Our findings provide practical insights into infectious disease containment and call for collaborative and coordinated global suppression efforts.

Managing borders during public health emergencies of international concern: a proposed typology of cross-border health measures.

BACKGROUND: The near universal adoption of cross-border health measures during the COVID-19 pandemic worldwide has prompted significant debate about their effectiveness and compliance with international law. The number of measures used, and the range of measures applied, have far exceeded previous public health emergencies of international concern. However, efforts to advance research, policy and practice to support their effective use has been hindered by a lack of clear and consistent definition. RESULTS: Based on a review of existing datasets for cross-border health measures, such as the Oxford Coronavirus Government Response Tracker and World Health Organization Public Health and Social Measures, along with analysis of secondary and grey literature, we propose six categories to define measures more clearly and consistently - policy goal, type of movement (travel and trade), adopted by public or private sector, level of jurisdiction applied, stage of journey, and degree of restrictiveness. These categories are then brought together into a proposed typology that can support research with generalizable findings and comparative analyses across jurisdictions. Addressing the current gaps in evidence about travel measures, including how different jurisdictions apply such measures with varying effects, in turn, enhances the potential for evidence-informed decision-making based on fuller understanding of policy trade-offs and externalities. Finally, through the adoption of standardized terminology and creation of an agreed evidentiary base recognized across jurisdictions, the typology can support efforts to strengthen coordinated global responses to outbreaks and inform future efforts to revise the WHO International Health Regulations (2005). CONCLUSIONS: The widespread use of cross-border health measures during the COVID-19 pandemic has prompted significant reflection on available evidence, previous practice and existing legal frameworks. The typology put forth in this paper aims to provide a starting point for strengthening research, policy and practice.

Two Imported Plasmodium falciparum Malaria Cases in Sanliurfa

In a 2017 data of World Health Organisation, malaria is still an important medical health care problem by threatening 217 million people and causing 435 thousand deaths. In our country, as a result of successful eradication programmes, any domestic cases were not encountered; however, approximately 200 import cases were seen each year from 2013 to 2017. This study aimed to create awareness for cases caused by P. falciparum that are increasingly seen in rare import cases, which displays more severe clinical course than other Plasmodium species.

Longitudinal study based on a safety registry for malaria patients treated with artenimol-piperaquine in six European countries.

BACKGROUND: European travellers to endemic countries are at risk of malaria and may be affected by a different range of co-morbidities than natives of endemic regions. The safety profile, especially cardiac issues, of artenimol (previously dihydroartemisinin)-piperaquine (APQ) Eurartesim® during treatment of uncomplicated imported falciparum malaria is not adequately described due to the lack of longitudinal studies in this population. The present study was conducted to partially fill this gap. METHODS: Participants were recruited through Health Care Provider's safety registry in 15 centres across 6 European countries in the period 2013-2016. Adverse events (AE) were collected, with a special focus on cardiovascular safety by including electrocardiogram QT intervals evaluated after correction with either Bazett's (QTcB) or Fridericia's (QTcF) methods, at baseline and after treatment. QTcB and/or QTcF prolongation were defined by a value > 450 ms for males and children and > 470 ms for females. RESULTS: Among 294 participants, 30.3% were women, 13.7% of Caucasian origin, 13.5% were current smoker, 13.6% current alcohol consumer and 42.2% declared at least one illness history. The mean (SD) age and body mass index were 39.8 years old (13.2) and 25.9 kg/m2 (4.7). Among them, 75 reported a total of 129 AE (27 serious), 46 being suspected to be related to APQ (11 serious) and mostly labelled as due to haematological, gastrointestinal, or infection. Women and Non-African participants had significantly (p < 0.05) more AEs. Among AEs, 21 were due to cardiotoxicity (7.1%), mostly QT prolongation, while 6 were due to neurotoxicity (2.0%), mostly dizziness. Using QTcF correction, QT prolongation was observed in 17/143 participants (11.9%), only 2 of them reporting QTcF > 500 ms (milliseconds) but no clinical symptoms. Using QTcB correction increases of > 60 ms were present in 9 participants (6.3%). A trend towards increased prolongation was observed in those over 65 years of age but only a few subjects were in this group. No new safety signal was reported. The overall efficacy rate was 255/257 (99.2%). CONCLUSIONS: APQ appears as an effective and well-tolerated drug for treatment of malaria in patients recruited in European countries. AEs and QT prolongation were in the range of those obtained in larger cohorts from endemic countries. Trial registration This study has been registered in EU Post-Authorization Studies Register as EUPAS6942.

Sustainable border control policy in the COVID-19 pandemic: A math modeling study.

BACKGROUND: Imported COVID-19 cases, if unchecked, can jeopardize the effort of domestic containment. We aim to find out what sustainable border control options for different entities (e.g., countries, states) exist during the reopening phases, given their own choice of domestic control measures. METHODS: We propose a SUIHR model, which has built-in imported risk and (1-tier) contact tracing to study the cross-border spreading and control of COVID-19. Under plausible parameter assumptions, we examine the effectiveness of border control policies, in combination with internal measures, to confine the virus and avoid reverting back to more restrictive life styles again. RESULTS: When the basic reproduction number R0 of COVID-19 exceeds 2.5, even 100% effective contact tracing alone is not enough to contain the spreading. For an entity that has completely eliminated the virus domestically, and resumes "normal", without mandatory institutional quarantine, even very strict border control measures combined with effective contact tracing can only delay another outbreak by 6 months. For entities employing a confining domestic control policy, non-increasing net imported cases is sufficient to remain open. CONCLUSIONS: Extremely strict border control in entities, where domestic spreading is currently eliminated (e.g., China), is justifiable. However such harsh measure are not necessary for other places. Entities successfully confining the virus by internal measures can open up to similar entities without additional border controls so long as the imported risk stays non-increasing. Opening the borders to entities lacking sufficient internal control of the virus should be exercised in combination with pre-departure screening and tests upon arrival.

International travel-related control measures to contain the COVID-19 pandemic: a rapid review.

BACKGROUND: In late 2019, the first cases of coronavirus disease 2019 (COVID-19) were reported in Wuhan, China, followed by a worldwide spread. Numerous countries have implemented control measures related to international travel, including border closures, travel restrictions, screening at borders, and quarantine of travellers. OBJECTIVES: To assess the effectiveness of international travel-related control measures during the COVID-19 pandemic on infectious disease transmission and screening-related outcomes. SEARCH METHODS: We searched MEDLINE, Embase and COVID-19-specific databases, including the Cochrane COVID-19 Study Register and the WHO Global Database on COVID-19 Research to 13 November 2020. SELECTION CRITERIA: We considered experimental, quasi-experimental, observational and modelling studies assessing the effects of travel-related control measures affecting human travel across international borders during the COVID-19 pandemic. In the original review, we also considered evidence on severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). In this version we decided to focus on COVID-19 evidence only. Primary outcome categories were (i) cases avoided, (ii) cases detected, and (iii) a shift in epidemic development. Secondary outcomes were other infectious disease transmission outcomes, healthcare utilisation, resource requirements and adverse effects if identified in studies assessing at least one primary outcome. DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and subsequently full texts. For studies included in the analysis, one review author extracted data and appraised the study. At least one additional review author checked for correctness of data. To assess the risk of bias and quality of included studies, we used the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool for observational studies concerned with screening, and a bespoke tool for modelling studies. We synthesised findings narratively. One review author assessed the certainty of evidence with GRADE, and several review authors discussed these GRADE judgements. MAIN RESULTS: Overall, we included 62 unique studies in the analysis; 49 were modelling studies and 13 were observational studies. Studies covered a variety of settings and levels of community transmission. Most studies compared travel-related control measures against a counterfactual scenario in which the measure was not implemented. However, some modelling studies described additional comparator scenarios, such as different levels of stringency of the measures (including relaxation of restrictions), or a combination of measures. Concerns with the quality of modelling studies related to potentially inappropriate assumptions about the structure and input parameters, and an inadequate assessment of model uncertainty. Concerns with risk of bias in observational studies related to the selection of travellers and the reference test, and unclear reporting of certain methodological aspects. Below we outline the results for each intervention category by illustrating the findings from selected outcomes. Travel restrictions reducing or stopping cross-border travel (31 modelling studies) The studies assessed cases avoided and shift in epidemic development. We found very low-certainty evidence for a reduction in COVID-19 cases in the community (13 studies) and cases exported or imported (9 studies). Most studies reported positive effects, with effect sizes varying widely; only a few studies showed no effect. There was very low-certainty evidence that cross-border travel controls can slow the spread of COVID-19. Most studies predicted positive effects, however, results from individual studies varied from a delay of less than one day to a delay of 85 days; very few studies predicted no effect of the measure. Screening at borders (13 modelling studies; 13 observational studies) Screening measures covered symptom/exposure-based screening or test-based screening (commonly specifying polymerase chain reaction (PCR) testing), or both, before departure or upon or within a few days of arrival. Studies assessed cases avoided, shift in epidemic development and cases detected. Studies generally predicted or observed some benefit from screening at borders, however these varied widely. For symptom/exposure-based screening, one modelling study reported that global implementation of screening measures would reduce the number of cases exported per day from another country by 82% (95% confidence interval (CI) 72% to 95%) (moderate-certainty evidence). Four modelling studies predicted delays in epidemic development, although there was wide variation in the results between the studies (very low-certainty evidence). Four modelling studies predicted that the proportion of cases detected would range from 1% to 53% (very low-certainty evidence). Nine observational studies observed the detected proportion to range from 0% to 100% (very low-certainty evidence), although all but one study observed this proportion to be less than 54%. For test-based screening, one modelling study provided very low-certainty evidence for the number of cases avoided. It reported that testing travellers reduced imported or exported cases as well as secondary cases. Five observational studies observed that the proportion of cases detected varied from 58% to 90% (very low-certainty evidence). Quarantine (12 modelling studies) The studies assessed cases avoided, shift in epidemic development and cases detected. All studies suggested some benefit of quarantine, however the magnitude of the effect ranged from small to large across the different outcomes (very low- to low-certainty evidence). Three modelling studies predicted that the reduction in the number of cases in the community ranged from 450 to over 64,000 fewer cases (very low-certainty evidence). The variation in effect was possibly related to the duration of quarantine and compliance. Quarantine and screening at borders (7 modelling studies; 4 observational studies) The studies assessed shift in epidemic development and cases detected. Most studies predicted positive effects for the combined measures with varying magnitudes (very low- to low-certainty evidence). Four observational studies observed that the proportion of cases detected for quarantine and screening at borders ranged from 68% to 92% (low-certainty evidence). The variation may depend on how the measures were combined, including the length of the quarantine period and days when the test was conducted in quarantine. AUTHORS' CONCLUSIONS: With much of the evidence derived from modelling studies, notably for travel restrictions reducing or stopping cross-border travel and quarantine of travellers, there is a lack of 'real-world' evidence. The certainty of the evidence for most travel-related control measures and outcomes is very low and the true effects are likely to be substantially different from those reported here. Broadly, travel restrictions may limit the spread of disease across national borders. Symptom/exposure-based screening measures at borders on their own are likely not effective; PCR testing at borders as a screening measure likely detects more cases than symptom/exposure-based screening at borders, although if performed only upon arrival this will likely also miss a meaningful proportion of cases. Quarantine, based on a sufficiently long quarantine period and high compliance is likely to largely avoid further transmission from travellers. Combining quarantine with PCR testing at borders will likely improve effectiveness. Many studies suggest that effects depend on factors, such as levels of community transmission, travel volumes and duration, other public health measures in place, and the exact specification and timing of the measure. Future research should be better reported, employ a range of designs beyond modelling and assess potential benefits and harms of the travel-related control measures from a societal perspective.

Study on the COVID-19 infection status, prevention and control strategies among people entering Shenzhen.

BACKGROUND: The novel coronavirus disease 2019 (COVID-19) confirmed cases overseas have continued to rise in the last months, and many people overseas have chosen to return to China. This increases the risk of a large number of imported cases which may cause a relapse of the COVID-19 outbreak. In order to prevent imported infection, the Shenzhen government has implemented a closed-loop management strategy using nucleic acid testing (NAT) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and requiring 14 days of medical observation for individuals with an overseas tour history (Hong Kong, Macao, Taiwan province and other countries). Our study aims to describe the status of COVID-19 infection among people entering Shenzhen, and to evaluate the effect of the closed-loop management strategy. METHODS: We undertook a descriptive study and risk analysis by the entry time, time of reporting, and local confirmed cases in countries of origin. The NAT were completed in Shenzhen Center for Disease Control and Prevention (CDC), ten district-level CDCs, and fever clinics. RESULTS: A total of 86,844 people from overseas entered Shenzhen from January 1 to April 18, 2020; there were 39 imported COVID cases and 293 close contacts. The infection rate of people entering was 4.49‰ [95% Confidence interval (CI): 3.26‰-6.05‰]. Fourteen imported cases (35.9%) came from the UK, and nine (23.08%) came from the USA. People entering from the USA since March 9 or from the UK since March 13 are the high-risk population. As of July 17, there have been no new confirmed cases in Shenzhen for 153 days, and the numbers of confirmed case, close contacts, and asymptomatic cases are 0. CONCLUSIONS: The closed-loop management has been effective in preventing imported infection and controlling domestic relapse. The distribution of entry time and report time for imported cases overseas was similar. This shows that it is important to implement closed-loop management at the port of entry.

Estimating the effect of selective border relaxation on COVID-19 in New Zealand.

AIMS: We developed a model, updated daily, to estimate undetected COVID-19 infections exiting quarantine following selectively opening New Zealand's borders to travellers from low-risk countries. METHODS: The prevalence of infectious COVID-19 cases by country was multiplied by expected monthly passenger volumes to predict the rate of arrivals. The rate of undetected infections entering the border following screening and quarantine was estimated. Level 1, Level 2 and Level 3 countries were defined as those with an active COVID-19 prevalence of up to 1/105, 10/105 and 100/105, respectively. RESULTS: With 65,272 travellers per month, the number of undetected COVID-19 infections exiting quarantine is 1 every 45, 15 and 31 months for Level 1, Level 2 and Level 3 countries, respectively. The overall rate of undetected active COVID-19 infections exiting quarantine is expected to increase from the current 0.40 to 0.50 per month, or an increase of one extra infection every 10 months. CONCLUSIONS: Loosening border restrictions results in a small increase in the rate of undetected COVID-19 infections exiting quarantine, which increases from the current baseline by one infection every 10 months. This information may be useful in guiding decision-making on selectively opening of borders in the COVID-19 era.

Estimating the risk of outbreaks of COVID-19 associated with shore leave by merchant ship crews: simulation studies for New Zealand.

AIM: We aimed to estimate the risk of COVID-19 outbreaks in a COVID-19-free destination country (New Zealand) associated with shore leave by merchant ship crews who were infected prior to their departure or on their ship. METHODS: We used a stochastic version of the SEIR model CovidSIM v1.1 designed specifically for COVID-19. It was populated with parameters for SARS-CoV-2 transmission, shipping characteristics and plausible control measures. RESULTS: When no control interventions were in place, we estimated that an outbreak of COVID-19 in New Zealand would occur after a median time of 23 days (assuming a global average for source country incidence of 2.66 new infections per 1,000 population per week, crews of 20 with a voyage length of 10 days and 1 day of shore leave per crew member both in New Zealand and abroad, and 108 port visits by international merchant ships per week). For this example, the uncertainty around when outbreaks occur is wide (an outbreak occurs with 95% probability between 1 and 124 days). The combination of PCR testing on arrival, self-reporting of symptoms with contact tracing and mask use during shore leave increased this median time to 1.0 year (14 days to 5.4 years, or a 49% probability within a year). Scenario analyses found that onboard infection chains could persist for well over 4 weeks, even with crews of only 5 members. CONCLUSION: This modelling work suggests that the introduction of SARS-CoV-2 through shore leave from international shipping crews is likely, even after long voyages. But the risk can be substantially mitigated by control measures such as PCR testing and mask use.

Control of COVID-19 in Australia through quarantine: the role of special health accommodation (SHA) in New South Wales, Australia.

BACKGROUND: The first COVID-19 cases were diagnosed in Australia on 25 January 2020. Initial epidiemiology showed that the majority of cases were in returned travellers from overseas. One aspect of Public Health response was to introduce compulsory 14 day quarantine for all travellers returning to New South Wales (NSW) by air or sea in Special Health Accommodation (SHA). We aim to outline the establishment of a specialised health quarantine accommodation service in the context of the COVID-19 pandemic, and describe the first month of COVID-19 screening. METHODS: The SHA was established with a comprehensive governance structure, remote clinical management through Royal Prince Alfred Virtual Hospital (rpavirtual) and site management with health care workers, NSW Police and accommodation staff. RESULTS: From 29 March to 29 April 2020, 373 returning travellers were admitted to the SHA from Sydney Airport. 88 (26.1%) of those swabbed were positive for SARS-CoV 2. The day of diagnosis of COVID-19 varied from Day 1 to Day 13, with 63.6% (n = 56) of these in the first week of quarantine. 50% of the people in the SHA were referred to rpavirtual for ongoing clinical management. Seven people required admission to hospital for ongoing clinical care. CONCLUSION: The Public Health response to COVID-19 in Australia included early and increased case detection through testing, tracing of contacts of confirmed cases, social distancing and prohibition of gatherings. In addition to these measures, the introduction of mandated quarantine for travellers to Australia was integral to the successful containment of COVID-19 in NSW and Australia through the prevention of transmission locally and interstate from returning travellers.