Fatal hemophagocytic lymphohistiocytosis-induced multiorgan dysfunction secondary to Burkholderia pseudomallei sepsis: A case report.

BACKGROUND: Burkholderia pseudomallei (B. pseudomallei) is a short, straight, medium-sized Gram-negative bacterium that mostly exists alone, without a capsule or spores, has more than three flagella at one end, and actively moves. B. pseudomallei confers high morbidity and mortality, with frequent granulocytopenia in B. pseudomallei sepsis-related deaths. However, mortality may be related to hemophagocytic lymphohistiocytosis (HLH) secondary to B. pseudomallei infection. CASE SUMMARY: A 12-year-old female was referred from a local hospital to the pediatric intensive care unit with suspected septic shock and fever, cough, dyspnea, and malaise. After admission, supportive symptomatic treatments including fluid resuscitation, anti-infective therapy, mechanical ventilation, and a vasoactive drug maintenance cycle were carefully initiated. The patient became unconscious, her blood pressure could not be maintained even under the exposure of vasoactive drugs, and she experienced cardiorespiratory arrest. The patient died due to ineffective high-quality in-hospital cardiopulmonary resuscitation. A subsequent bone marrow smear examination revealed extensive phagocytosis, and the blood culture was positive for B. pseudomallei. Family history revealed a sibling death from B. pseudomallei sepsis 5 years earlier. CONCLUSION: The higher mortality rate in patients with B. pseudomallei sepsis may be related to secondary HLH after infection, wherein multiorgan dysfunction syndrome may be directly related to infection or immune damage caused by secondary HLH. Patients with B. pseudomallei can be asymptomatic and can become an infective source.

Optimal control and cost-effectiveness analysis of age-structured malaria model with asymptomatic carrier and temperature variability.

This paper presents an age-structured mathematical model for malaria transmission dynamics with asymptomatic carrier and temperature variability. The temperature variability function is fitted to the temperature data, and the malaria model is then fitted to the malaria cases and validated to check its suitability. Time-dependent controls were considered, including Long Lasting Insecticide Nets, treatment of symptomatic, screening and treatment of asymptomatic carriers and spray of insecticides. Pontryagin's Maximum Principle is used to derive the necessary conditions for optimal control of the disease. The numerical simulations of the optimal control problem reveal that the strategy involving the combination of all four controls is the most effective in reducing the number of infected individuals. Furthermore, the cost-effectiveness analysis shows that treatment of symptomatic, screening and treatment of asymptomatic carriers and insecticide spraying is the most cost-effective strategy to implement to control malaria transmission when available resources are limited.

Seroprevalence and risk factors of tropical theileriosis in smallholder asymptomatic large ruminants in Egypt.

Knowledge of the prevalence and epidemiological determinants of tropical theileriosis in large ruminants, particularly in the asymptomatic carrier, is crucial for designing and implementing effective host-specific control measures. This study aimed to estimate the seroprevalence of tropical theileriosis in asymptomatic cattle and water buffaloes and identify the potential risk factors of theileriosis in large ruminants raised under smallholder-production system in Egypt. A cross-sectional study was conducted in five districts of the Sharkia governorate from March 2019 to February 2020. In total, 350 serum samples were collected from cattle and water buffaloes under smallholder-production system and tested for Theileria annulata antibodies using the indirect antibody fluorescence test (IFAT). Data on species, host characteristics, presence of ticks, season, and districts were collected at sampling using a questionnaire. A multivariable mixed-effects logistic regression model was built to determine the potential risk factors associated with T. annulate seropositivity of the animals. The overall apparent seroprevalence of T. annulata in 350 tested animals was 70%. In the univariable analyses, cattle compared to buffaloes, younger animals compared to older ones, animals with ticks on their bodies, and warmer seasons were all associated with a higher likelihood of seropositive results in the study population while sex of the animals was not associated with seropositivity. The final multivariable model showed that animals with ticks on their bodies had 3.5× higher odds of seropositivity than those with no ticks (P < 0.001), and warmer seasons were associated with the higher odds of infection compared to winter (P = 0.003). The high seroprevalence of tropical theileriosis in the study region indicates that the disease is endemic among smallholders of large ruminants. The identified risk factors of T. annulata-seropositivity in asymptomatic carrier animals provides evidence-based guidance for adopting effective intervention measures.

Burden of chronic hepatitis B and C infections in 2015 and future trends in Japan: A simulation study.

Background: Determining the number of chronic hepatitis B (HBV) and C virus (HCV) infections is essential to assess the progress towards the World Health Organization 2030 viral hepatitis elimination goals. Using data from the Japanese National Database (NDB), we calculated the number of chronic HBV and HCV infections in 2015 and predicted the trend until 2035. Methods: NDB and first-time blood donors data were used to calculate the number of chronic HBV and HCV infections in 2015. A Markov simulation was applied to predict chronic infections until 2035 using transition probabilities calculated from NDB data. Findings: The total number of chronic HBV and HCV infections in 2015 in Japan was 1,905,187-2,490,873 (HCV:877,841-1,302,179, HBV:1,027,346-1,188,694), of which 923,661-1,509,347 were undiagnosed or diagnosed but not linked to care ("not engaged in care"), and 981,526 were engaged in care. Chronic HBV and HCV infections are expected to be 923,313-1,304,598 in 2030, and 739,118-1,045,884 in 2035. Compared to 2015, by 2035, the number of persons with HCV not engaged in care will decline by 59·8 - 76·1% and 86·5% for patients in care. For HBV, a 47·3 - 49·3% decrease is expected for persons not engaged in care and a decline of 26·0% for patients engaged in care. Interpretation: Although the burden of HBV and HCV is expected to decrease by 2035, challenges in controlling hepatitis remain. Improved and innovative screening strategies with linkage to care for HCV cases, and a functional cure for HBV are needed. Funding: Japan Ministry of Health, Labour and Welfare.

Epidemiologic characteristics and differential management strategies of seven case series with COVID-19 outbreaks caused by asymptomatic carriers from June 2020 to May 2021 in China.

With the COVID-19 epidemic quickly under control in China in the early stage of 2020, global cooperation/communications may pose great challenges to epidemic control and prevention in the country. Large-scale spread by asymptomatic carriers was a concern. We obtained data on new cluster outbreak regions with COVID-19 caused by asymptomatic carriers from June 2020 to May 2021 in China, and reported the epidemiological characteristics, the possible routes of viral transmission and infection, and different control strategies. These results show the importance of regular screening for high-risk populations and differential management strategies for epidemic control, which provide an objective basis for suppressing the spread of the SARS-CoV-2 virus. These experiences can be used as a reference to minimize the subsequent spread of virus mutants in various places.

Seven Years of Selective Genetic Screening Program and Follow-Up of Asymptomatic Carriers With Hereditary Transthyretin Amyloidosis in Bulgaria.

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, autosomal-dominant (AD) multisystem disorder resulting from the extracellular deposition of amyloid fibrils formed by a destabilized mutant form of transthyretin (TTR), a transport protein predominantly produced by the liver. Aim: The aims of the current study are to demonstrate the Bulgarian experience with the screening programs among the high-risk patient population over the last 7 years, to present the results from the therapy with TTR stabilizer in our cohort, as well as to stress on the importance of a follow-up of asymptomatic carriers with TTR pathogenic variants by a multidisciplinary team of specialists. Materials and Methods: In 2014, a screening program among the high-risk patient population for ATTRv was initiated in Bulgaria. On one hand, it was conducted to identify new patients and families among people with "red flag" clinical features, while on the other hand, the program aimed to identify TTR mutation carriers among the families with already genetically proven diagnoses. Sanger sequencing methodology was used to make fast target testing for mutations in the TTR gene in the suspected individuals. All of the identified carriers underwent subsequent evaluation for neurological, cardiac, gastroenterological, and neuro-ophthalmological involvement. Those considered affected were provided with multidisciplinary treatment and a follow-up. Results: As a result of a 7-year selective screening program among the high-risk patient population and relatives of genetically verified affected individuals, 340 carriers of TTR mutations were identified in Bulgaria with the following gene defects: 78.53% with Glu89Gln, 10.29% with Val30Met, 8.24% with Ser77Phe, 2.06% with Gly47Glu, and 0.59% with Ser52Pro. All of these affected displayed a mixed phenotype with variable ages at onset and rate of progression, according to their mutation. From the 150 patients treated with TTR stabilizer, 84 remained stable, while in other 66 patients the treatment was terminated either because of polyneuropathy progression or due to death. A program for a regular follow-up of asymptomatic carriers in the last 3 years enabled us to detect the transition of 39/65 to symptomatic patients and to initiate treatment in a timely manner. Conclusion: Bulgarian ATTRv patients display a mixed phenotype with some clinical peculiarities for each mutation that should be considered when treating the affected and the follow-up of the asymptomatic carriers of a specific gene defect.

Comparative genomic and transmission analysis of Clostridioides difficile between environmental, animal, and clinical sources in China.

Clostridioides difficile is the most common pathogen causing antibiotic-associated diarrhea. Previous studies showed that diverse sources, aside from C. difficile infection (CDI) patients, played a major role in C. difficile hospital transmission. This study aimed to investigate relationships and transmission potential of C. difficile strains from different sources. A prospective study was conducted both in the intensive care unit (ICU) and six livestock farms in China in 2018-2019. Ninety-eight strains from CDI patients (10 isolates), asymptomatic hospitalized carriers (55), the ICU environment (12), animals (14), soil (4), and farmers (3) were collected. Sequence type (ST) 3/ribotype (RT) 001, ST35/RT046, and ST48/RT596 were dominant types, distributed widely in multiple sources. Core-genome single-nucleotide polymorphism (cgSNP) analysis showed that hospital and farm strains shared several common clonal groups (CGs, strains separated by ≤ 2 cgSNPs) (CG4/ST3/RT001, CG7/ST35/RT046, CG11/ST48/RT596). CDI patients, asymptomatic carriers, and the ICU environment strains also shared several common CGs. The number of virulence genes was not statistically different between strains from different sources. Multi-source strains in the same CG carried identical virulence gene sequences, including pathogenicity genes at the pathogenicity locus and adhesion-related genes at S-layer cassette. Resistance genes (ermB, tetM, etc.) were widespread in multiple sources, and multi-source strains in the same CG had similar resistance phenotypes and carried consistent transposons and plasmid types. The study indicated that interspecies and cross-regional transmission of C. difficile occurs between animals, the environment, and humans. Community-associated strains from both farms and asymptomatic hospitalized carriers were important reservoirs of CDI in hospitals.

Epidemiological Characteristics of Sporadic Nosocomial COVID-19 Infections From June 2020 to June 2021 in China: An Overview of Vaccine Breakthrough Infection Events.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has wreaked havoc on millions of people around the world. Although China quickly brought the Coronavirus disease (COVID-19) under control, there have been several sporadic outbreaks in different regions of China since June 2020. This article described the chronological nosocomial COVID-19 infection events related to several sporadic outbreaks of SARS-CoV-2 in different regions of China. We have reported epidemiological characteristics and management measures of sporadic nosocomial COVID-19 infections from June 2020 to June 2021 and specially focused on the domestic COVID-19 breakthrough infection in China, such as domestic COVID-19 breakthrough infection-a vaccinated healthcare professional working in the isolation ward of a designated COVID-19 hospital.

Distinct Infection Forms of SARS-CoV-2 Among People Living With HIV.

Background: People living with HIV (PLWH) are immunodeficient, it is vague if they are more susceptible to SARS-CoV-2 infection than HIV negative individuals. Methods: In this cross-sectional study, 857 PLWH and 1048 HIV negative individuals were enrolled from the Wuchang district in Wuhan, China. We compared the total rate of SARS-CoV-2 infection, the rate of COVID-19, asymptomatic carriers, and unapparent infectors in the two groups. The risk factors associated with SARS-CoV-2 infection among PLWH were explored. Results: Fourteen out of 857 (1.63%) PLWH were infected with SARS-CoV-2, while 68 of 1048 (6.49%) HIV negative individuals were infected. In PLWH, there were 6 confirmed COVID-19 (0.70%), 4 asymptomatic carriers (0.47%) and 4 unapparent infectors (0.47%). In the HIV negative group, the cases of COVID-19, asymptomatic carrier, and unapparent infector were 5 (0.48%), 0 (0.00%), and 63 (6.01%), respectively. After adjusting for age, gender, and chronic comorbidities, the rate of SARS-CoV-2 infection in PLWH was lower than that in HIV negative group (1.96% vs 5.74%, P = 0.001). The morbidity of COVID-19 was similar between the two groups (P = 0.107), but the rate of unapparent infection in PLWH was lower than that in the HIV negative group (0.54% vs 5.46%, P = 0.001). Older age (aOR = 4.50, 95%CI: 1.34-15.13, P = 0.015) and OIs (aOR = 9.59, 95%CI: 1.54-59.92, P = 0.016) were risk factors for SARS-CoV-2 infection among PLWH. Conclusions: PLWH has different infection forms of SARS-CoV-2 compared with the general population. Older age and OIs were considered to driving causes of SARS-CoV-2 infection among PLWH.

The prevalence of asymptomatic carriers of COVID-19 as determined by routine preoperative testing.

BACKGROUND: The coronavirus disease SARS-CoV-2 (COVID-19) has swiftly spread throughout the globe, greatly influencing all aspects of life. As in previous pandemics, concerns for limited resources and a sustainable medical workforce have been on the forefront of infrastructure modifications. Consequently, surgical specialties have needed to consider each surgical case for necessity and safety during the COVID-19 outbreak. At our institution, availability of SARS-CoV-2 assay has allowed preoperative testing of asymptomatic surgical patients. AIM/OBJECTIVE: To better define the prevalence of asymptomatic carriers in a surgical population and to better understand the impact of testing on our personal protective equipment (PPE) supply. METHODS: We began routine, preoperative testing for all asymptomatic patients coming to our academic medical centre on 30 March 2020. Scheduled surgeries were deemed urgent by the surgeon with a review for appropriateness by a novel surgical committee. A retrospective patient chart review was performed. Emergency surgeries were excluded. Asymptomatic patients with positive test results had their surgeries rescheduled at the discretion of the surgeon and patient. Patients who tested negative underwent surgery with staff using standard PPE. RESULTS: Eighty-four asymptomatic surgical patients were tested preoperatively with three (3.6%) testing positive for SARS-CoV-2. Preoperative testing saved 498 N95 respirators over this time period. DISCUSSION: This is the first report of routine COVID-19 preoperative testing in an asymptomatic surgical population. Within this population, there is a 3.6% rate of asymptomatic SARS-CoV-2 carriers. Through this practice, personnel exposure can be minimised and access to PPE can be preserved.

COVID-19: Asymptomatic Carrier: An Autopsy Case Report.

The severe acute respiratory syndrome (SARS)-coronavirus- 2 (CoV-2) outbreak in Wuhan, China has now spread to many countries across the world including the India with an increasing death toll. On March 11, 2020, the new clinical condition COVID-19 (Corona-Virus-Disease-19) was declared a pandemic by the World Health Organization (WHO). Owing to its infectivity, high risk of transmission, and limited handling of dead bodies, published data on the course of diseases has been limited. Most patients with COVID-19 have a mild disease course and remain as asymptomatic carrier; however, few patients of older age and with co-morbidites develop severe disease leading on to fatality. If due to COVID-19 infection death occurs, an autopsy is unlikely. However in unnatural deaths the legal duty impels the proper performance of a full autopsy, to find out the cause and manner of death. The detailed autopsy examination along with histo-pathological findings in the organs of asymptomatic patient of COVID-19 and its comparison with microscopic findings in Aluminium Phosphide poisoning are discussed below. This will summarizes the research status for COVID-19 deaths, which will be important for evaluation of cause of death, prevention, control and clinical strategies of COVID-19.

Staged progression epidemic models for the transmission of invasive nontyphoidal Salmonella (iNTS) with treatment.

We develop and analyze a stage-progression compartmental model to study the emerging invasive nontyphoidal Salmonella (iNTS) epidemic in sub-Saharan Africa. iNTS bloodstream infections are often fatal, and the diverse and non-specific clinical features of iNTS make it difficult to diagnose. We focus our study on identifying approaches that can reduce the incidence of new infections. In sub-Saharan Africa, transmission and mortality are correlated with the ongoing HIV epidemic and severe malnutrition. We use our model to quantify the impact that increasing antiretroviral therapy (ART) for HIV infected adults and reducing malnutrition in children would have on mortality from iNTS in the population. We consider immunocompromised subpopulations in the region with major risk factors for mortality, such as malaria and malnutrition among children and HIV infection and ART coverage in both children and adults. We parameterize the progression rates between infection stages using the branching probabilities and estimated time spent at each stage. We interpret the basic reproduction number R0 as the total contribution from an infinite infection loop produced by the asymptomatic carriers in the infection chain. The results indicate that the asymptomatic HIV+ adults without ART serve as the driving force of infection for the iNTS epidemic. We conclude that the worst disease outcome is among the pediatric population, which has the highest infection rates and death counts. Our sensitivity analysis indicates that the most effective strategies to reduce iNTS mortality in the studied population are to improve the ART coverage among high-risk HIV+ adults and reduce malnutrition among children.

Plasmodium-a brief introduction to the parasites causing human malaria and their basic biology.

Malaria is one of the most devastating infectious diseases of humans. It is problematic clinically and economically as it prevails in poorer countries and regions, strongly hindering socioeconomic development. The causative agents of malaria are unicellular protozoan parasites belonging to the genus Plasmodium. These parasites infect not only humans but also other vertebrates, from reptiles and birds to mammals. To date, over 200 species of Plasmodium have been formally described, and each species infects a certain range of hosts. Plasmodium species that naturally infect humans and cause malaria in large areas of the world are limited to five-P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi. The first four are specific for humans, while P. knowlesi is naturally maintained in macaque monkeys and causes zoonotic malaria widely in South East Asia. Transmission of Plasmodium species between vertebrate hosts depends on an insect vector, which is usually the mosquito. The vector is not just a carrier but the definitive host, where sexual reproduction of Plasmodium species occurs, and the parasite's development in the insect is essential for transmission to the next vertebrate host. The range of insect species that can support the critical development of Plasmodium depends on the individual parasite species, but all five Plasmodium species causing malaria in humans are transmitted exclusively by anopheline mosquitoes. Plasmodium species have remarkable genetic flexibility which lets them adapt to alterations in the environment, giving them the potential to quickly develop resistance to therapeutics such as antimalarials and to change host specificity. In this article, selected topics involving the Plasmodium species that cause malaria in humans are reviewed.

Clinical course and challenging management of early COVID-19 infection after heart transplantation: case report of two patients.

BACKGROUND: There are limited data on Coronavirus disease 2019 (COVID-19) in solid organ transplant patients, especially in heart transplant recipients, with only a few case reports and case series described so far. Heart transplant recipients may be at particular high risk due to their comorbidities and immunosuppressed state. CASE PRESENTATION: This report describes the clinical course and the challenging management of early COVID-19 infection in two heart transplant recipients who tested positive for the SARS-CoV-2 virus in the perioperative period of the transplant procedure. The two patients developed a severe form of the disease and ultimately died despite the initiation of an antiviral monotherapy with hydroxychloroquine coupled with the interruption of mycophenolate mofetil. CONCLUSIONS: These two cases illustrate the severity and poor prognosis of COVID-19 in the perioperative period of a heart transplant. Thorough screening of donors and recipients is mandatory, and the issue of asymptomatic carriers needs to be addressed.

The Positive Rate of Nucleic Acid Testing and the Epidemiological Characteristics of COVID-19 in Chongqing.

OBJECTIVE: The purpose of this study is to analyze the positive rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleic acid testing (NAT), cases of and deaths due to SARS-CoV-2, and the epidemiological characteristics of SARS-CoV-2 to identify high-risk populations. METHODS: A retrospective study in Jiulongpo district of Chongqing was conducted by performing continuous observations of the frequency of SARS-CoV-2 NAT, analyzing the data of close contacts of patients and asymptomatic carriers, and collecting epidemiological data. Data were collected from January 20, 2020, when the first case of SARS-CoV-2 infection was reported, to March 26, 2020. Descriptive statistical analysis and Cochrane-Mantel-Haenszel analysis were used to compare the positive detection rates and positive diagnostic rates of different exposure groups. RESULTS: A total of 7,118 people received 10,377 SARS-CoV-2 nucleic acid tests in one district, and the SARS-CoV-2 positive rates were 0.40% (18/4446) and 0.15% (4/2672) in people receiving one and ≥ two nucleic acid tests (p = 0.06), respectively. Those with suspected cases (12.35%) and close contacts (8%) had higher positive rates than people tested at fever clinics (0.39%) (p < 0.001). The median latency (range) of cases was 5 (2, 9) days, and the median time from diagnosis to recovery was 22 (14, 25) days. One recovered patient received a positive test result at 28 days after recovery when she attempted to donate blood. Six clustered cases, including one patient who died, indicated persistent human-to-human transmission. One patient who was diagnosed after death was found to have infected 13 close contacts. People working in catering and other public service departments (36.36%) and people who are unemployed and retirees (45.45%) have an increased risk of infection compared with technical staff (9.09%) and farmers (9.09%). CONCLUSION: The total positive rate was low in the tested population, and more effective detection ranges should be defined to improve precise and differentiated epidemic control strategies. Moreover, in asymptomatic carriers, SARS-CoV-2 tests were positive after recovery, and patients with suspected SARS-CoV-2 infection who die may pose serious potential transmission threats.

Emergence of ciprofloxacin-resistant Neisseria meningitidis B from asymptomatic carriers during an outbreak in Peru, 2017.

Asymptomatic carriers are a likely source of transmission of Neisseria meningitidis to close contacts who are placed at a higher risk for invasive meningococcal disease (IMD). Although N. meningitidis ciprofloxacin-resistance is rare, there have been an increase in the reports of resistant isolates mainly in patients diagnosed with IMD, and little is known about the N. meningitidis ciprofloxacin-resistance in the carrier populations. We performed a pharyngeal carriage study during a 2017 military setting outbreak in Peru, caused by a ciprofloxacin-resistant N. meningitidis B. The isolates analysed came from two hospitalized cases and six asymptomatic carriers. Whole-genome sequence-based analysis was performed and showed that strains carrying the Thr91Ile mutation, in the gene encoding for subunit A of DNA gyrase (gyrA), were responsible for the fluoroquinolone resistance (MICs ≥0.256 µg ml-1) and were closely related to highly virulent strains from France, Norway and the UK. Phylogenetic analysis of the gyrA gene revealed that likely these Peruvian isolates acquired resistance through horizontal gene transfer from Neisseria lactamica. Our study provides evidence for the emergence and propagation of ciprofloxacin-resistant N. meningitidis B from asymptomatic carriers, and recommends the introduction of serogroup B vaccines for high-risk populations.

The epidemiological characteristics of cluster transmission of coronavirus disease 2019 (COVID-19): a multi-center study in Jiangsu Province.

Coronavirus Disease 2019 (COVID-19) pandemic has rapidly spread across the globe while little multi-center research about the epidemiological characteristics of cluster transmission is conducted. To provide a more comprehensive description of the epidemiological characteristics of cluster transmission and the virulence of SARS-CoV-2 carried by asymptomatic carriers, we studied the epidemiological characteristics of 70 clusters. 70 clusters including 311 consecutive subjects from January 20, 2020, to March 10, 2020, were enrolled. Of 70 clusters, 5 were infected by asymptomatic or presymptomatic carriers. We gathered and analyzed information about their demographic, epidemiological, clinical, diagnostic classification, and cluster characteristics. Among the 66 asymptomatic carriers in Jiangsu Province, 49 asymptomatic were observed in 311 subjects distributed in 70 clusters. We demonstrated that there is a significance between the severity of cases infected by asymptomatic carriers and cases infected by symptomatic patients (P=0.033) and the former usually presented with milder symptoms. A significant difference was shown regarding the level distribution of age (P=0.006) and the frequency distribution of gender (P=0.014) and disease severity of COVID-19 (P=0.008) among the seven groups classified by the relationship with the index cases. The average age of infected medical staff was the youngest and the majority of infected medical are females while the infected patients were generally oldest and usually accompanied by severest symptoms. We concluded that asymptomatic carriers are mainly screened out of clusters and the patients infected by asymptomatic carriers present with milder symptoms than those infected by symptomatic patients, which indicated that the SARS-CoV-2 shares decreased virulence among asymptomatic carriers. Effective measures should be taken to prevent transmission in hospitals to protect doctors, nurses, and patients.

Digital PCR is a sensitive new technique for SARS-CoV-2 detection in clinical applications.

The global coronavirus disease 2019 (COVID-19) pandemic has posed great challenges in people's daily lives. Highly sensitive laboratory techniques played a critical role in clinical COVID-19 diagnosis and management. In this study the feasibility of using a new digital PCR-based detection assay for clinical COVID-19 diagnosis was investigated by comparing its performance with that of RT-PCR. Clinical patient samples and samples obtained from potentially contaminated environments were analyzed. The study included 10 patients with confirmed COVID-19 diagnoses, 32 validated samples of various types derived from different clinical timepoints and sites, and 148 environmentally derived samples. SARS-CoV-2 nucleic acids were more readily detected in respiratory tract samples (35.0%). In analyses of environmentally derived samples, the positivity rate of air samples was higher than that of surface samples, probably due to differences in virus concentrations. Digital PCR detected SARS-CoV-2 in several samples that had previously been deemed negative, including 3 patient-derived samples and 5 environmentally derived samples. In this study digital PCR exhibited higher sensitivity than conventional RT-PCR, suggesting that it may be a useful new method for clinical SARS-CoV-2 detection. Improvement of SARS-CoV-2 detection would substantially reduce the rates of false-negative COVID-19 test results, in particular those pertaining to asymptomatic carriers.

Viral Transmission and Clinical Features in Asymptomatic Carriers of SARS-CoV-2 in Wuhan, China.

We report the clinical characteristics, viral shedding duration, and contact tracing for asymptomatic carriers of SARS-CoV-2 in Wuhan, China. The asymptomatic carriers were relatively young (median age: 34.5 years). Chest computed tomography showed no abnormalities. The nasopharyngeal swab was an optimum specimen for RNA testing. The median viral shedding duration was 11.5 days. Notably, 2 months of viral shedding duration were reported in two nurses, which was much longer than previously reported or than usually thought. The transmissibility of SARS-CoV-2 by asymptomatic carriers during the studied period in Wuhan appeared to be weak. Only one patient (1/12) was found to have transmitted the virus to another person. Early asymptomatic carrier detection, isolation, and contact tracing could be useful to mitigate the spread of the disease.