PIN51 Role of Asymptomatic Carriers in the Transmission of COVID-19: A Review

Cutaneous dirofilariasis is a parasitic disease caused by the mosquito-borne filarial nematodesDirofilaria (Nochtiella) repens, living in the subcutaneous tissue of dogs, cats, wild carnivores, and humans. Cases have been recently reported also from Germany, Czech Republic, Hungary, Ukraine, Russia, Austria, Switzerland, France, The Netherlands, and the Middle East.D. repensis not widely known to cause chronic pruritic dermatitis in animals. Dermatological signs observed in 100 canine clinic cases were pruritus (100%), erythema (79%), papulae (62%), focal or multifocal alopecia (55%), hyperkeratosis (18%), crusting (14%), nodules (12%), acantosis (5%), and eczema (3%). Signs other than dermatological were conjunctivitis (46%), anorexia (35%), vomiting (26%), fever (25%), lethargy (20%), and lymph-adenomegaly (10%). A case imported from Italy to Dubai is described. The opportunistic role ofD. repensmight explain the presence of asymptomatic carriers, the concurrent observation of nondermatological signs, and the development of dermatitis in a subgroup of parasitized dogs.

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A national survey of testing and management of asymptomatic carriage of C. difficile

Infection Control and Hospital Epidemiology ◽

10.1017/ice.2019.109 ◽

2019 ◽

Vol 40 (7) ◽

pp. 801-803 ◽

Cited By ~ 3

Author(s):

Preeta K. Kutty ◽

Susan E. Beekmann ◽

Ronda L. Sinkowitz-Cochran ◽

Erik R. Dubberke ◽

David T. Kuhar ◽

...

Keyword(s):

Best Practices ◽

National Survey ◽

Nationwide Survey ◽

Asymptomatic Carriers ◽

Healthcare Settings ◽

Asymptomatic Carriage

AbstractA nationwide survey indicated that screening for asymptomatic carriers of C. difficile is an uncommon practice in US healthcare settings. Better understanding of the role of asymptomatic carriage in C. difficile transmission, and of the measures available to reduce that risk, are needed to inform best practices regarding the management of carriers.

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Use of Multilocus Variable Number of Tandem Repeats Analysis Genotyping to Determine the Role of Asymptomatic Carriers in Clostridium difficile Transmission

Clinical Infectious Diseases ◽

10.1093/cid/cit475 ◽

2013 ◽

Vol 57 (8) ◽

pp. 1094-1102 ◽

Cited By ~ 144

Author(s):

Scott R. Curry ◽

Carlene A. Muto ◽

Jessica L. Schlackman ◽

A. William Pasculle ◽

Kathleen A. Shutt ◽

...

Keyword(s):

Clostridium Difficile ◽

Tandem Repeats ◽

Variable Number ◽

Asymptomatic Carriers

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Role of asymptomatic carriers and weather variables in persistent transmission of malaria in an endemic district of Assam, India

Infection Ecology & Epidemiology ◽

10.3402/iee.v5.25442 ◽

2015 ◽

Vol 5 (1) ◽

pp. 25442 ◽

Cited By ~ 5

Author(s):

Nani Gopal Das ◽

Sunil Dhiman ◽

Pranab Kumar Talukdar ◽

Diganta Goswami ◽

Bipul Rabha ◽

...

Keyword(s):

Weather Variables ◽

Asymptomatic Carriers ◽

Endemic District

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Phylogenomics and population genomics of SARS-CoV-2 in Mexico reveals variants of interest (VOI) and a mutation in the Nucleocapsid protein associated with symptomatic versus asymptomatic carriers

10.1101/2021.05.18.21256128 ◽

2021 ◽

Author(s):

Francisco Barona-Gomez ◽

Luis Delaye ◽

Erik Diaz-Valenzuela ◽

Fabien Plisson ◽

Arely Cruz-Perez ◽

...

Keyword(s):

Nucleocapsid Protein ◽

Population Genomics ◽

Bimodal Distribution ◽

Central Mexico ◽

Binding Motif ◽

Single Nucleotide Variants ◽

Nucleocapsid Proteins ◽

Asymptomatic Carriers ◽

Genetic Patterns

Understanding the evolution of SARS-CoV-2 virus in various regions of the world during the Covid19 pandemic is of the utmost importance to help mitigate the effects of this devastating disease. We describe the phylogenomic and population genetic patterns of the virus in Mexico during the pre-vaccination stage, including asymptomatic carriers. Our RT-qPCR screening and phylogenomics directed a sequence/structure analysis of the Spike glycoprotein, revealing mutation of concern E484K in genomes from central Mexico, in addition to the nationwide prevalence of the imported variant 20C/S:452R (B.1.427/9). Overall, the detected variants in Mexico show mutations in the N-terminal domain (i.e., R190M), in the receptor-binding motif (i.e., T478K, E484K), within the S1-S2 subdomains (i.e., P681R/H, T732A), and at the basis of the protein, V1176F, raising concerns about the lack of phenotypic and clinical data available for the postulated variants of interest (VOIs) 20B/478K.V1 and P.3. Moreover, the population patterns of Single Nucleotide Variants (SNVs) from symptomatic and asymptomatic carriers sampled with a self-sampling scheme, revealed a bimodal distribution of polymorphisms in all three sampled localities from central Mexico, and confirmed the presence of several fixed variants, mostly from the 241T-3037T-14408T-23403G haplotype common in Asia. Despite gene flow among Mexican localities, we found differences in both the allelic frequencies among localities and the allelic imbalance of the mutation S194L of the nucleocapsid protein between symptomatic and asymptomatic carriers. Our results highlight the dual role of Spike and Nucleocapsid proteins in adaptive evolution of SARS-CoV-2 to their hosts and provide a baseline for specific follow-up of mutations of concern during the vaccination stage in Mexico.

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Role of Asymptomatic Carriers in Long-Term Care Facility Clostridioides (Clostridium) difficile Transmission

Clostridium Difficile Infection in Long-Term Care Facilities ◽

10.1007/978-3-030-29772-5_3 ◽

2019 ◽

pp. 25-36

Author(s):

Ravina Kullar ◽

Ellie J. C. Goldstein

Keyword(s):

Clostridium Difficile ◽

Long Term Care ◽

Care Facility ◽

Term Care ◽

Term Care Facility ◽

Asymptomatic Carriers ◽

Long Term Care Facility

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Hidden Perils: Diagnosing Asymptomatic Disease Carriers

Medicine Anthropology Theory | An open-access journal in the anthropology of health illness and medicine ◽

10.17157/mat.8.2.5106 ◽

2021 ◽

Vol 8 (2) ◽

pp. 1-29

Author(s):

Ilana Löwy

Keyword(s):

New York ◽

Asymptomatic Carrier ◽

Laboratory Diagnosis ◽

Asymptomatic Carriers ◽

Free Carriers ◽

Research Article ◽

History Of ◽

Asymptomatic Disease ◽

Apparently Healthy

COVID-19, a disease induced by SARS-CoV-2, became a worldwide pandemic while SARS, a disease induced by a closely related virus, SARS-CoV, was successfully contained. This is because COVID-19, unlike SARS, can be spread by people who do not display any symptoms of disease, either because they are in the early stages of the infection or because their infection remains clinically silent. This research article traces the complex history of the diagnosis of symptom-free (or asymptomatic) carriers of pathogens, a term inseparably linked to the rise of the laboratory diagnosis of pathogens. Only such a diagnosis can reveal that an apparently healthy individual harbours dangerous bacteria, parasites, or viruses. The article begins with the iconic story of ‘Typhoid Mary’, a New York cook found to be an asymptomatic carrier of typhoid fever microbes. It then discusses divergent approaches to the treatment of symptom-free carriers of hookworm and controversies around the screening of HIV carriers, especially before the development of anti-retroviral treatments. It concludes with a presentation of the debates on the role of asymptomatic carriers in the spread of COVID-19 and of the differences between the approaches of countries seeking to eliminate this disease, a goal that itself entails tracing and isolation of all asymptomatic carriers of coronavirus, and those trying to contain it, an approach that tolerates the presence of a limited number of ‘invisible’ virus carriers.

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Shedding of Viable Virus in Asymptomatic SARS-CoV-2 Carriers

mSphere ◽

10.1128/msphere.00019-21 ◽

2021 ◽

Vol 6 (3) ◽

Author(s):

Takayuki Murata ◽

Aki Sakurai ◽

Masahiro Suzuki ◽

Satoshi Komoto ◽

Tomihiko Ide ◽

...

Keyword(s):

Reverse Transcription ◽

Potential Role ◽

Nonstructural Protein ◽

Rt Pcr ◽

Asymptomatic Carriers ◽

Reverse Transcription Pcr ◽

The Impact ◽

Crossing Point ◽

Pcr Test

ABSTRACT Information regarding the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic carriers is scarce. In order to determine the duration of infectivity and its correlation with reverse transcription-PCR (RT-PCR) results and time since initial positive PCR test in this population, we evaluated SARS-CoV-2 cell infectivity in nasopharyngeal samples longitudinally obtained from asymptomatic carriers who disembarked from a cruise ship during a COVID-19 outbreak. Of 166 nasopharyngeal samples collected from 39 asymptomatic carriers every 48 h until two consecutive negative PCR test results were obtained, SARS-CoV-2 was successfully isolated from 9 PCR-positive samples which were obtained from 7 persons (18%; 7/39). Viable viruses were isolated predominantly within 7 days after the initial positive PCR test, except for one person who shed viable virus until day 15. The median crossing point (Cp) value of RT-PCR of culture-positive samples was 24.6 (interquartile range [IQR], 20.4 to 25.8; range, 17.9 to 30.3), and Cp values were significantly associated with isolation of viable virus (odds ratio, 0.496; 95% confidence interval [CI], 0.329 to 0.747; P value, 0.001), which was consistent with existing data for symptomatic patients. Genome sequence analysis of SARS-CoV-2 samples consecutively obtained from a person who shed viable virus for 15 days identified the emergence of two novel single nucleotide variants (C8626T transition and C18452T transition) in the sample collected on day 15, with the latter corresponding to an amino acid substitution in nonstructural protein 14. The impact of these mutations on prolonged viable-virus shedding is unclear. These findings underscore the potential role of asymptomatic carriers in transmission. IMPORTANCE A growing number of studies suggest the potential role of asymptomatic SARS-CoV-2 carriers as a major driver of the COVID-19 pandemic; however, virological assessment of asymptomatic infection has largely been limited to reverse transcription-PCR (RT-PCR), which can be persistently positive without necessarily indicating the presence of viable virus (e.g., replication-competent virus). Here, we evaluated the infectivity of asymptomatic SARS-CoV-2 carriers by detecting SARS-CoV-2-induced cytopathic effects on Vero cells using longitudinally obtained nasopharyngeal samples from asymptomatic carriers. We show that asymptomatic carriers can shed viable virus until 7 days after the initial positive PCR test, with one outlier shedding until day 15. The crossing point (Cp) value of RT-PCR was the leading predictive factor for virus viability. These findings provide additional insights into the role of asymptomatic carriers as a source of transmission and highlight the importance of universal source control measures, along with isolation policy for asymptomatic carriers.

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