Potential applicability of the importation risk index for predicting the risk of rarely imported infectious diseases.

BACKGROUND: There have been many prediction studies for imported infectious diseases, employing air-travel volume or the importation risk (IR) index, which is the product of travel-volume and disease burden in the source countries, as major predictors. However, there is a lack of studies validating the predictability of the variables especially for infectious diseases that have rarely been reported. In this study, we analyzed the prediction performance of the IR index and air-travel volume to predict disease importation. METHODS: Rabies and African trypanosomiasis were used as target diseases. The list of rabies and African trypanosomiasis importation events, annual air-travel volume between two specific countries, and incidence of rabies and African trypanosomiasis in the source countries were obtained from various databases. RESULTS: Logistic regression analysis showed that IR index was significantly associated with rabies importation risk (p value < 0.001), but the association with African trypanosomiasis was not significant (p value = 0.923). The univariable logistic regression models showed reasonable prediction performance for rabies (area under curve for Receiver operating characteristic [AUC] = 0.734) but poor performance for African trypanosomiasis (AUC = 0.641). CONCLUSIONS: Our study found that the IR index cannot be generally applicable for predicting rare importation events. However, it showed the potential utility of the IR index by suggesting acceptable performance in rabies models. Further studies are recommended to explore the generalizability of the IR index's applicability and to propose disease-specific prediction models.

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.

Risk Assessment of Importation and Local Transmission of COVID-19 in South Korea: Statistical Modeling Approach.

BACKGROUND: Despite recent achievements in vaccines, antiviral drugs, and medical infrastructure, the emergence of COVID-19 has posed a serious threat to humans worldwide. Most countries are well connected on a global scale, making it nearly impossible to implement perfect and prompt mitigation strategies for infectious disease outbreaks. In particular, due to the explosive growth of international travel, the complex network of human mobility enabled the rapid spread of COVID-19 globally. OBJECTIVE: South Korea was one of the earliest countries to be affected by COVID-19. In the absence of vaccines and treatments, South Korea has implemented and maintained stringent interventions, such as large-scale epidemiological investigations, rapid diagnosis, social distancing, and prompt clinical classification of severely ill patients with appropriate medical measures. In particular, South Korea has implemented effective airport screenings and quarantine measures. In this study, we aimed to assess the country-specific importation risk of COVID-19 and investigate its impact on the local transmission of COVID-19. METHODS: The country-specific importation risk of COVID-19 in South Korea was assessed. We investigated the relationships between country-specific imported cases, passenger numbers, and the severity of country-specific COVID-19 prevalence from January to October 2020. We assessed the country-specific risk by incorporating country-specific information. A renewal mathematical model was employed, considering both imported and local cases of COVID-19 in South Korea. Furthermore, we estimated the basic and effective reproduction numbers. RESULTS: The risk of importation from China was highest between January and February 2020, while that from North America (the United States and Canada) was high from April to October 2020. The R0 was estimated at 1.87 (95% CI 1.47-2.34), using the rate of α=0.07 for secondary transmission caused by imported cases. The Rt was estimated in South Korea and in both Seoul and Gyeonggi. CONCLUSIONS: A statistical model accounting for imported and locally transmitted cases was employed to estimate R0 and Rt. Our results indicated that the prompt implementation of airport screening measures (contact tracing with case isolation and quarantine) successfully reduced local transmission caused by imported cases despite passengers arriving from high-risk countries throughout the year. Moreover, various mitigation interventions, including social distancing and travel restrictions within South Korea, have been effectively implemented to reduce the spread of local cases in South Korea.

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.

Effectiveness of Containment Measures Against COVID-19 in Singapore: Implications for Other National Containment Efforts.

BACKGROUND: We hypothesize that comprehensive surveillance of COVID-19 in Singapore has facilitated early case detection and prompt contact tracing and, with community-based measures, contained spread. We assessed the effectiveness of containment measures by estimating transmissibility (effective reproduction number, (Equation is included in full-text article.)) over the course of the outbreak. METHODS: We used a Bayesian data augmentation framework to allocate infectors to infectees with no known infectors and determine serial interval distribution parameters via Markov chain Monte Carlo sampling. We fitted a smoothing spline to the number of secondary cases generated by each infector by respective onset dates to estimate (Equation is included in full-text article.)and evaluated increase in mean number of secondary cases per individual for each day's delay in starting isolation or quarantine. RESULTS: As of April 1, 2020, 1000 COVID-19 cases were reported in Singapore. We estimated a mean serial interval of 4.6 days [95% credible interval (CI) = 4.2, 5.1] with a SD of 3.5 days (95% CI = 3.1, 4.0). The posterior mean (Equation is included in full-text article.)was below one for most of the time, peaking at 1.1 (95% CI = 1.0, 1.3) on week 9 of 2020 due to a spreading event in one of the clusters. Eight hundred twenty-seven (82.7%) of cases infected less than one person on average. Over an interval of 7 days, the incremental mean number of cases generated per individual for each day's delay in starting isolation or quarantine was 0.03 cases (95% CI = 0.02, 0.05). CONCLUSIONS: We estimate that robust surveillance, active case detection, prompt contact tracing, and quarantine of close contacts kept (Equation is included in full-text article.)below one.

Epidemiology of imported infectious diseases, China, 2014-18.

BACKGROUND: The frequent movement of population between countries brings an increasing number of travel-related infections. This study aims to define the spectrum and dynamics of imported infections observed from international travel in the Chinese mainland. METHODS: Sick travellers were screened by inbound sentinel surveillance and post-travel clinic visits from 2014 to 18. The infections were classified as respiratory, gastrointestinal, vector-borne, blood/sexually transmitted and mucocutaneous. The analysed variables included the place of origin of the travellers (Chinese or foreign) and the time when travel-related infection was present (at the time of return, during travel and post-travel visits to the clinic). RESULTS: In total, 58 677 cases were identified amongst 1 409 265 253 travellers, with an incidence of 41.64/million, comprising during-travel incidence of 27.44/million and a post-travel incidence of 14.20/million. Respiratory infections constituted the highest proportion of illnesses during travel (81.19%, 31 393 of 38 667), which mainly came from Asian countries and tourists; with influenza virus and rhinovirus infections being mainly diagnosed. Vector-borne diseases constituted the highest proportion of post-travel illnesses (98.14%, 19 638 of 20 010), which were mainly diagnosed from African countries and labourers; with malaria and dengue fever being mainly diagnosed. The differential infection spectrum varied in terms of the traveller's demography, travel destination and travel purpose. As such, a higher proportion of foreign travellers had blood/sexually transmitted diseases (89.85%, 2832 of 3152), while Chinese citizens had a higher prevalence of vector-borne diseases (85.98%, 19 247 of 22 387) and gastrointestinal diseases (79.36%, 1115 of 1405). The highest incidence rate was observed amongst travellers arriving from Africa, while the lowest was observed amongst travellers arriving from Europe. CONCLUSIONS: The findings might help in preparing recommendations for travellers and also aid in primary care or other clinics that prepare travellers before trips abroad. The findings will also help to identify locations and the associated types of infections that might require attention.

Risk Assessment and Management of COVID-19 Among Travelers Arriving at Designated U.S. Airports, January 17-September 13, 2020.

In January 2020, with support from the U.S. Department of Homeland Security (DHS), CDC instituted an enhanced entry risk assessment and management (screening) program for air passengers arriving from certain countries with widespread, sustained transmission of SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). The objectives of the screening program were to reduce the importation of COVID-19 cases into the United States and slow subsequent spread within states. Screening aimed to identify travelers with COVID-19-like illness or who had a known exposure to a person with COVID-19 and separate them from others. Screening also aimed to inform all screened travelers about self-monitoring and other recommendations to prevent disease spread and obtain their contact information to share with public health authorities in destination states. CDC delegated postarrival management of crew members to airline occupational health programs by issuing joint guidance with the Federal Aviation Administration.* During January 17-September 13, 2020, a total of 766,044 travelers were screened, 298 (0.04%) of whom met criteria for public health assessment; 35 (0.005%) were tested for SARS-CoV-2, and nine (0.001%) had a positive test result. CDC shared contact information with states for approximately 68% of screened travelers because of data collection challenges and some states' opting out of receiving data. The low case detection rate of this resource-intensive program highlighted the need for fundamental change in the U.S. border health strategy. Because SARS-CoV-2 infection and transmission can occur in the absence of symptoms and because the symptoms of COVID-19 are nonspecific, symptom-based screening programs are ineffective for case detection. Since the screening program ended on September 14, 2020, efforts to reduce COVID-19 importation have focused on enhancing communications with travelers to promote recommended preventive measures, reinforcing mechanisms to refer overtly ill travelers to CDC, and enhancing public health response capacity at ports of entry. More efficient collection of contact information for international air passengers before arrival and real-time transfer of data to U.S. health departments would facilitate timely postarrival public health management, including contact tracing, when indicated. Incorporating health attestations, predeparture and postarrival testing, and a period of limited movement after higher-risk travel, might reduce risk for transmission during travel and translocation of SARS-CoV-2 between geographic areas and help guide more individualized postarrival recommendations.

Epidemiology, clinical pattern and impact of species-specific molecular diagnosis on management of leishmaniasis in Belgium, 2010-2018: A retrospective study.

BACKGROUND: Species-directed therapy of leishmaniasis has been recommended for travelers since 2014, but little is known about species distribution and treatment practices in non-endemic countries. We aimed to describe leishmaniasis cases in Belgium since species typing became available and evaluate its impact on patient management. METHOD: Retrospective analysis of all patients diagnosed by PCR at our national reference laboratory from 2010 to 2018. Species were typed by Hsp-70 sequencing. RESULTS: We identified 18 visceral leishmaniasis (VL) and 147 (muco)cutaneous leishmaniasis ((M)CL) cases. VL was exclusively due to L. infantum and consistently treated with liposomal amphotericin B, with four observed failures. (M)CL was caused by ten different species. Of 62 cases diagnosed and species typed after 2014 with timing information, 28 (45.2%) were treated before the species result was available. Therapy was not species-directed in 10/32(28.1%) of those treated after species identification. Patients treated according to the guidelines tended to have a favorable outcome more often than those who were not (36/44, 81.8% versus 8/19, 57.9%; p = 0.045). CONCLUSIONS: In contrast to VL, various species caused (M)CL in our setting and species result was often not considered for treatment. Outcome tended to be better however when therapy was species-directed.

Malaria Risk Map Using Spatial Multi-Criteria Decision Analysis along Yunnan Border During the Pre-elimination Period.

In moving toward malaria elimination, finer scale malaria risk maps are required to identify hotspots for implementing surveillance-response activities, allocating resources, and preparing health facilities based on the needs and necessities at each specific area. This study aimed to demonstrate the use of multi-criteria decision analysis (MCDA) in conjunction with geographic information systems (GISs) to create a spatial model and risk maps by integrating satellite remote-sensing and malaria surveillance data from 18 counties of Yunnan Province along the China-Myanmar border. The MCDA composite and annual models and risk maps were created from the consensus among the experts who have been working and know situations in the study areas. The experts identified and provided relative factor weights for nine socioeconomic and disease ecology factors as a weighted linear combination model of the following: ([Forest coverage × 0.041] + [Cropland × 0.086] + [Water body × 0.175] + [Elevation × 0.297] + [Human population density × 0.043] + [Imported case × 0.258] + [Distance to road × 0.030] + [Distance to health facility × 0.033] + [Urbanization × 0.036]). The expert-based model had a good prediction capacity with a high area under curve. The study has demonstrated the novel integrated use of spatial MCDA which combines multiple environmental factors in estimating disease risk by using decision rules derived from existing knowledge or hypothesized understanding of the risk factors via diverse quantitative and qualitative criteria using both data-driven and qualitative indicators from the experts. The model and fine MCDA risk map developed in this study could assist in focusing the elimination efforts in the specifically identified locations with high risks.

Epidemiology and control of meticillin-resistant Staphylococcus aureus in Stockholm County, Sweden, 2000 to 2016: overview of a "search-and-contain" strategy.

To review the epidemiology and measures to control meticillin-resistant Staphylococcus aureus, MRSA, in Stockholm between 2000 and 2016 from the perspective of the Department of Communicable Disease Control and Prevention, Stockholm County Council, Sweden. Age, sex, and place of acquisition of their MRSA on all patients reported to the department were reviewed. Measures for control included surveillance through mandatory reporting of cases, screening patients with risk factors for MRSA, strict adherence to basic nursing hygienic principles, isolation of MRSA positive patients in single rooms in dedicated MRSA wards, and cohorting of staff. An MRSA team was created at the Department of Infectious Diseases, Karolinska University Hospital, for follow-up of all cases. Several administrative meetings and cooperative groups were formed that are still in function. From 2000 to 2016, there were 7373 MRSA cases reported. Healthcare-associated MRSA, HA-MRSA, was successfully controlled, and from 2006 onwards, very limited HA-MRSA transmission or outbreaks occurred. However, incidence increased overall, from 9.5 per 100,000 in 2000 to 37.3 per 100,000 in 2016, due to increase of MRSA acquired abroad and of MRSA acquired in the Swedish community. Surveillance and control measures have been successful in containing HA-MRSA in Stockholm, Sweden, but incidence has increased substantially due to imported cases and spread in the Swedish community. The strategy may be termed "search-and-contain" since screening, infection control, follow-up, and advice on personal hygiene were cornerstones of control, whereas eradication of carriage was not.

Chronic hepatitis B virus case-finding in UK populations born abroad in intermediate or high endemicity countries: an economic evaluation.

OBJECTIVES: The majority (>90%) of new or undiagnosed cases of hepatitis B virus (HBV) in the UK are among individuals born in countries with intermediate or high prevalence levels (≥2%). We evaluate the cost-effectiveness of increased HBV case-finding among UK migrant populations, based on a one-time opt out case-finding approach in a primary care setting. DESIGN: Cost-effectiveness evaluation. A decision model based on a Markov approach was built to assess the progression of HBV infection with and without treatment as a result of case-finding. The model parameters, including the cost and effects of case-finding and treatment, were estimated from the literature. All costs were expressed in 2017/2018 British Pounds (GBPs) and health outcomes as quality-adjusted life-years (QALYs). INTERVENTION: Hepatitis B virus case-finding among UK migrant populations born in countries with intermediate or high prevalence levels (≥2%) in a primary care setting compared with no intervention (background testing). RESULTS: At a 2% hepatitis B surface antigen (HBsAg) prevalence, the case-finding intervention led to a mean incremental cost-effectiveness ratio of £13 625 per QALY gained which was 87% and 98% likely of being cost-effective at willingness to pay (WTP) thresholds of £20 000 and £30 000 per additional QALY, respectively. Sensitivity analyses indicated that the intervention would remain cost-effective under a £20 000 WTP threshold as long as HBsAg prevalence among the migrant population is at least 1%. However, the results were sensitive to a number of parameters, especially the time horizon and probability of treatment uptake. CONCLUSIONS: HBV case-finding using a one-time opt out approach in primary care settings is very likely to be cost-effective among UK migrant populations with HBsAg prevalence ≥1% if the WTP for an additional QALY is around £20 000.

[Establishment of Geographic Information System on risk assessment regarding infectious diseases imported to China].

Objectives: To establish a geographic information application system for analyzing the spatial and temporal distribution of major infectious diseases in various regions of the world and to assess the risk of importation of those diseases, to China. Methods: We collected and integrated the following information on: 1) outbreaks and areas of epidemics of major infectious diseases in the world from 2000 to 2017, 2) cases of infectious diseases in arriving travelers through active surveillance at international entry-exit ports in mainland China from 2014 to 2016, 3) numbers of annual global international flights and travelers in the country. With the above information, a global space-time distribution database on major infectious diseases was then established, using the technology related to the system. Models regarding technologies on time-space analysis, probabilistic risk assessment and geographic information visualization, were applied to establish a geographic information system on risk assessment of infectious diseases that imported to China. Results: Through integration of information on outbreaks and epidemic areas of 60 major infectious diseases in 220 countries and regions around the world, as well as 42 kinds of infectious diseases identified among the international arrivals in mainland China, a system was then developed. Information on the distribution of major infectious diseases and their potential risks in the worldwide various regions, characteristics of spectrum and disease burden of infectious diseases imported to each province of mainland China were displayed. Thus, risks on importing infectious diseases in each province via air way were able to be evaluated and simulated by the probabilistic risk assessment model, under the information on specific kind of infectious disease, outside China. Conclusion: Geographic Information System on Risk Assessment Regarding Infectious Diseases Imported to China provides basic data for epidemiological reconnaissance and assessment on risks of importing infectious diseases outside China, thus would be helpful for the improvement of strategies on surveillance, prevention and control regarding the importing infectious diseases, in China.

The Clinical Impact and Cost-effectiveness of Measles-Mumps-Rubella Vaccination to Prevent Measles Importations Among International Travelers From the United States.

BACKGROUND: Measles importations and the subsequent spread from US travelers returning from abroad are responsible for most measles cases in the United States. Increasing measles-mumps-rubella (MMR) vaccination among departing US travelers could reduce the clinical impact and costs of measles in the United States. METHODS: We designed a decision tree to evaluate MMR vaccination at a pretravel health encounter (PHE), compared with no encounter. We derived input parameters from Global TravEpiNet data and literature. We quantified Riskexposure to measles while traveling and the average number of US-acquired cases and contacts due to a measles importation. In sensitivity analyses, we examined the impact of destination-specific Riskexposure, including hot spots with active measles outbreaks; the percentage of previously-unvaccinated travelers; and the percentage of travelers returning to US communities with heterogeneous MMR coverage. RESULTS: The no-encounter strategy projected 22 imported and 66 US-acquired measles cases, costing $14.8M per 10M travelers. The PHE strategy projected 15 imported and 35 US-acquired cases at $190.3M per 10M travelers. PHE was not cost effective for all international travelers (incremental cost-effectiveness ratio [ICER] $4.6M/measles case averted), but offered better value (ICER <$100 000/measles case averted) or was even cost saving for travelers to hot spots, especially if travelers were previously unvaccinated or returning to US communities with heterogeneous MMR coverage. CONCLUSIONS: PHEs that improve MMR vaccination among US international travelers could reduce measles cases, but are costly. The best value is for travelers with a high likelihood of measles exposure, especially if the travelers are previously unvaccinated or will return to US communities with heterogeneous MMR coverage.

[Transmission risk matrix assessment of imported leishmaniasis in China].

OBJECTIVE: To assess the risk of imported leishmaniasis in China, offering scientific evidences for leishmaniasis prevention and control. METHODS: The expert consultation method was used to establish a risk index system, and the risk matrix was used to evaluate the risk scales of leishmaniasis. RESULTS: This risk assessment indicator system included 3 first-grade indexes and 13 second-grade indexes to the aspect of risk probability. Five indexes were also included on the aspect of the risk hazard severity in this system. The transmission risk matrix assessment showed that the risk of imported leishmaniasis transmission in China was in low risk level. CONCLUSIONS: This risk matrix assessment is applied for the transmission of imported leishmaniasis in China in the first time, indicating the potential risk of imported leishmaniasis in China.

Risk assessment of malaria transmission at the border area of China and Myanmar.

BACKGROUND: In order to achieve the goal of malaria elimination, the Chinese government launched the National Malaria Elimination Programme in 2010. However, as a result of increasing cross-border population movements, the risk of imported malaria cases still exists at the border areas of China, resulting in a potential threat of local transmission. The focus of this paper is to assess the Plasmodium vivax incidences in Tengchong, Yunnan Province, at the border areas of China and Myanmar. METHODS: Time series of P. vivax incidences in Tengchong from 2006 to 2010 are collected from the web-based China Information System for Disease Control and Prevention, which are further separated into time series of imported and local cases. First, the seasonal and trend decomposition are performed on time series of imported cases using Loess method. Then, the impact of climatic factors on the local transmission of P. vivax is assessed using both linear regression models (LRM) and generalized additive models (GAM). Specifically, the notion of vectorial capacity (VCAP) is used to estimate the transmission potential of P. vivax at different locations, which is calculated based on temperature and rainfall collected from China Meteorological Administration. RESULTS: Comparing with Ruili County, the seasonal pattern of imported cases in Tengchong is different: Tengchong has only one peak, while Ruili has two peaks during each year. This may be due to the different cross-border behaviors of peoples in two locations. The vectorial capacity together with the imported cases and the average humidity, can well explain the local incidences of P. vivax through both LRM and GAM methods. Moreover, the maximum daily temperature is verified to be more suitable to calculate VCAP than the minimal and average temperature in Tengchong County. CONCLUSION: To achieve malaria elimination in China, the assessment results in this paper will provide further guidance in active surveillance and control of malaria at the border areas of China and Myanmar.

Cost analysis of measles in refugees arriving at Los Angeles International Airport from Malaysia.

Background On August 24, 2011, 31 US-bound refugees from Kuala Lumpur, Malaysia (KL) arrived in Los Angeles. One of them was diagnosed with measles post-arrival. He exposed others during a flight, and persons in the community while disembarking and seeking medical care. As a result, 9 cases of measles were identified. Methods We estimated costs of response to this outbreak and conducted a comparative cost analysis examining what might have happened had all US-bound refugees been vaccinated before leaving Malaysia. Results State-by-state costs differed and variously included vaccination, hospitalization, medical visits, and contact tracing with costs ranging from $621 to $35,115. The total of domestic and IOM Malaysia reported costs for US-bound refugees were $137,505 [range: $134,531 - $142,777 from a sensitivity analysis]. Had all US-bound refugees been vaccinated while in Malaysia, it would have cost approximately $19,646 and could have prevented 8 measles cases. Conclusion A vaccination program for US-bound refugees, supporting a complete vaccination for US-bound refugees, could improve refugees' health, reduce importations of vaccine-preventable diseases in the United States, and avert measles response activities and costs.