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Journal of Medical Virology Dec 2022SARS-CoV-2 Omicron variant seemed to cause milder disease compared to previous predominated variants. We aimed to conduct a meta-analysis to assess the pooled... (Meta-Analysis)
Meta-Analysis
SARS-CoV-2 Omicron variant seemed to cause milder disease compared to previous predominated variants. We aimed to conduct a meta-analysis to assess the pooled proportion of nonsevere disease and asymptomatic infection among COVID-19 patients infected with Omicron and Delta. We searched PubMed, Embase, Web of Science, and China National Knowledge Infrastructure (CNKI) databases. We included studies of SARS-CoV-2 Omicron infection from November 1, 2021, to April 18, 2022, and studies of Delta infection from October 1, 2020, to June 30, 2022. Studies without corresponding data, with less than 50 patients, or obviously biased concerning main outcome were excluded. Meta-analysis was performed in R 4.2.0 with the "meta" package. Subgroup analyses were conducted by study group and vaccination status. The pooled proportion of asymptomatic infection and nonsevere disease with Omicron were 25.5% (95% confidence interval [CI] 17.0%-38.2%) and 97.9% (95% CI 97.1%-98.7%), significantly higher than those of Delta with 8.4% (95% CI 4.4%-16.2%) and 91.4% (95% CI 87.0%-96.0%). During Omicron wave, children and adolescents had higher proportion of asymptomatic infection, SOTR and the elderly had lower proportion of nonsevere disease, vaccination of a booster dose contributed to higher proportion of both asymptomatic infection and nonsevere disease. This study estimates the pooled proportion of asymptomatic infection and nonsevere disease caused by SARS-CoV-2 Omicron compared to other predominant variants. The result has important implications for future policy making.
Topics: Adolescent; Aged; Asymptomatic Infections; COVID-19; Child; China; Humans; SARS-CoV-2
PubMed: 35961786
DOI: 10.1002/jmv.28066 -
Parasites & Vectors Oct 2023Asymptomatic infection is the most common outcome of exposure to Leishmania parasites. In the Mediterranean region, where Leishmania infantum is endemic, studies on the...
BACKGROUND
Asymptomatic infection is the most common outcome of exposure to Leishmania parasites. In the Mediterranean region, where Leishmania infantum is endemic, studies on the prevalence of asymptomatic infection have often relied on serological testing in blood donors. In Spain, regional studies have shown seroprevalence in blood donors between 1 and 8%; in Portugal, values of 0 and 2% were suggested by two localized studies, in different populations. The purpose of this study was (i) to estimate the prevalence of asymptomatic Leishmania infection in blood donors in mainland Portugal, and (ii) to study the association between the detection of antibodies to Leishmania and sociodemographic factors, and also the knowledge, perceptions and practices (KPP) of the blood donors regarding leishmaniasis.
METHODS
A cross-sectional study targeted the population of people who donated blood in mainland Portugal. Participants, distributed proportionally by municipality and aged between 18 and 65 years, were selected randomly in 347 blood collection points between February and June 2022, and completed a sociodemographic and a KPP questionnaire. Detection of anti-Leishmania antibodies in serum was performed using an ELISA commercial kit. Individual KPP scores were calculated by adding grades defined for each question.
RESULTS
Globally, 201/3763 samples were positive. The estimated national true seroprevalence was 4.8% (95% CI 4.1-5.5%). The proportion of positive results was significantly different between NUTS (Nomenclature of Territorial Units for Statistics) regions. Models suggested that seropositivity was significantly higher in male sex, people older than 25 years, or residing in the Centro NUTS2 region, but not in dog owners nor people with lower KPP scores. Overall, 72.3% of participants had previously heard of leishmaniasis and, in multivariate analysis, a higher Knowledge score was associated with age 25-40 years, female sex, ownership of dogs, and higher education.
CONCLUSIONS
Global estimated true seroprevalence (4.8%) was similar to previous regional studies in blood donors in neighboring Spain. Higher seroprevalence values in the NUTS2 Centro region were consistent with incidence data from humans and seroprevalence studies in dogs. On the other hand, the low values in the Alentejo and the high values in the northern subregions may be the result of geographical shifts in parasite circulation due to climate change and should prompt localized and integrated, vector, canine, and human research, following a One Health approach.
Topics: Humans; Male; Animals; Dogs; Female; Adolescent; Young Adult; Adult; Middle Aged; Aged; Portugal; Blood Donors; Asymptomatic Infections; Seroepidemiologic Studies; Prevalence; Cross-Sectional Studies; Dog Diseases; Leishmaniasis; Leishmania infantum; Antibodies, Protozoan; Leishmaniasis, Visceral
PubMed: 37817278
DOI: 10.1186/s13071-023-05980-1 -
Antimicrobial Agents and Chemotherapy Aug 2022Malaria control relies on passive case detection, and this strategy fails detecting asymptomatic infections. In addition, infections in endemic areas harbor multiple...
Malaria control relies on passive case detection, and this strategy fails detecting asymptomatic infections. In addition, infections in endemic areas harbor multiple parasite genotypes that could affect case management and malaria epidemiology. Here, we performed AmpSeq genotyping to capture polymorphisms associated with antimalarial resistance and the genetic diversity within natural Plasmodium falciparum infections. Known genetic polymorphisms associated with altered drug susceptibility were screened for the five most common marker genes, , , , , and , and genetic diversity was established from two known AmpSeq markers, and . Relative abundance of the different genotypes within mixed infections was calculated from the number of reads per genotype. Genotyping was performed on 117 samples, 63 from asymptomatic and 54 from symptomatic individuals. We identified up to 15 genotypes within an infection, and the median multiplicity of infection was higher in asymptomatic infections (median MOI = 5 in asymptomatics versus median MOI = 2 in symptomatics, 0.001). No genetic differentiation on parasites from asymptomatic and symptomatic individuals was found. No mutation associated with ART resistance was identified. Prevalence of the P. falciparum chloroquine resistance wild-type genotype (CVMNK) reached 80%, confirming a return to chloroquine (CQ) sensitive parasites in Cameroon. In addition, the CQ-associated resistant genotype (CVIET) was present at very low density in polyclonal infections. Persistence of low-density chloroquine resistant parasites indicates competition-survival trade-offs may contribute to maintaining genetic diversity . Thus, monitoring the expansion of these low-density genotypes in different immune backgrounds will be critical to evaluate drug policy changes.
Topics: Antimalarials; Asymptomatic Infections; Chloroquine; Drug Resistance; Folic Acid Antagonists; Genotype; Humans; Malaria; Malaria, Falciparum; Mutation; Plasmodium falciparum; Protozoan Proteins
PubMed: 35862750
DOI: 10.1128/aac.00188-22 -
BMC Infectious Diseases Jul 2021Infection with Salmonella enterica usually results in diarrhea, fever, and abdominal cramps, but some people become asymptomatic or chronic carrier as a source of...
BACKGROUND
Infection with Salmonella enterica usually results in diarrhea, fever, and abdominal cramps, but some people become asymptomatic or chronic carrier as a source of infection for others. This study aimed to analyze the difference in serotype, antimicrobial resistance, and genetic profiles between Salmonella strains isolated from patients and those from asymptomatic people in Nantong city, China.
METHODS
A total of 88 Salmonella strains were collected from patients and asymptomatic people from 2017 to 2018. Serotyping, antimicrobial susceptibility testing, and PFGE analysis were performed to analyze the characteristics of these strains.
RESULTS
Twenty serotypes belonging to 8 serogroups were identified in the 88 Salmonella strains. S. Typhimurium remained to be the predominant serotype in strains from both patients and asymptomatic people. Among the 27 strains from patients, S. Enteritidis and S. Rissen were shown as the other two major serotypes, while S. London, S. Derby, and S. Meleagridis were demonstrated as the other significant serotypes among the 61 strains from asymptomatic people. Antimicrobial resistance testing revealed that 84.1% of strains from both resources were multi-drug resistant. PFGE displayed a highly discriminative ability to differentiate strains belonging to S. Derby, S. Typhimurium, etc., but could not efficiently differentiate serotypes like S. Enteritidis.
CONCLUSIONS
This study's results demonstrated that S. Typhimurium could cause human infection in both symptomatic and asymptomatic state; S. London, S. Derby, and S. Meleagridis usually cause asymptomatic infection, while S. Enteritidis infection mainly results in human diseases. The high multi-drug resistance rate detected in the antimicrobial resistance and diverse PFGE profiles of these strains implied that the strains were isolated from different sources, and the increased surveillance of Salmonella from both patients and asymptomatic people should be taken to control the disease.
Topics: Adolescent; Adult; Aged; Asymptomatic Infections; Child; Child, Preschool; China; Drug Resistance, Multiple, Bacterial; Electrophoresis, Gel, Pulsed-Field; Female; Humans; Infant; Male; Microbial Sensitivity Tests; Middle Aged; Salmonella; Salmonella Infections; Serogroup; Serotyping
PubMed: 34210275
DOI: 10.1186/s12879-021-06340-z -
PLoS Medicine Sep 2020There is disagreement about the level of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We conducted a living systematic review and... (Meta-Analysis)
Meta-Analysis
BACKGROUND
There is disagreement about the level of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We conducted a living systematic review and meta-analysis to address three questions: (1) Amongst people who become infected with SARS-CoV-2, what proportion does not experience symptoms at all during their infection? (2) Amongst people with SARS-CoV-2 infection who are asymptomatic when diagnosed, what proportion will develop symptoms later? (3) What proportion of SARS-CoV-2 transmission is accounted for by people who are either asymptomatic throughout infection or presymptomatic?
METHODS AND FINDINGS
We searched PubMed, Embase, bioRxiv, and medRxiv using a database of SARS-CoV-2 literature that is updated daily, on 25 March 2020, 20 April 2020, and 10 June 2020. Studies of people with SARS-CoV-2 diagnosed by reverse transcriptase PCR (RT-PCR) that documented follow-up and symptom status at the beginning and end of follow-up or modelling studies were included. One reviewer extracted data and a second verified the extraction, with disagreement resolved by discussion or a third reviewer. Risk of bias in empirical studies was assessed with an adapted checklist for case series, and the relevance and credibility of modelling studies were assessed using a published checklist. We included a total of 94 studies. The overall estimate of the proportion of people who become infected with SARS-CoV-2 and remain asymptomatic throughout infection was 20% (95% confidence interval [CI] 17-25) with a prediction interval of 3%-67% in 79 studies that addressed this review question. There was some evidence that biases in the selection of participants influence the estimate. In seven studies of defined populations screened for SARS-CoV-2 and then followed, 31% (95% CI 26%-37%, prediction interval 24%-38%) remained asymptomatic. The proportion of people that is presymptomatic could not be summarised, owing to heterogeneity. The secondary attack rate was lower in contacts of people with asymptomatic infection than those with symptomatic infection (relative risk 0.35, 95% CI 0.10-1.27). Modelling studies fit to data found a higher proportion of all SARS-CoV-2 infections resulting from transmission from presymptomatic individuals than from asymptomatic individuals. Limitations of the review include that most included studies were not designed to estimate the proportion of asymptomatic SARS-CoV-2 infections and were at risk of selection biases; we did not consider the possible impact of false negative RT-PCR results, which would underestimate the proportion of asymptomatic infections; and the database does not include all sources.
CONCLUSIONS
The findings of this living systematic review suggest that most people who become infected with SARS-CoV-2 will not remain asymptomatic throughout the course of the infection. The contribution of presymptomatic and asymptomatic infections to overall SARS-CoV-2 transmission means that combination prevention measures, with enhanced hand hygiene, masks, testing tracing, and isolation strategies and social distancing, will continue to be needed.
Topics: Asymptomatic Diseases; Asymptomatic Infections; Betacoronavirus; COVID-19; Coronavirus Infections; Disease Progression; Humans; Mass Screening; Pandemics; Pneumonia, Viral; Reverse Transcriptase Polymerase Chain Reaction; SARS-CoV-2
PubMed: 32960881
DOI: 10.1371/journal.pmed.1003346 -
PLoS Neglected Tropical Diseases Sep 2018Among the neglected tropical diseases, leishmaniasis continues to be prevalent in many tropical and subtropical countries despite international, national, and local... (Review)
Review
BACKGROUND
Among the neglected tropical diseases, leishmaniasis continues to be prevalent in many tropical and subtropical countries despite international, national, and local efforts towards its control and elimination over the last decade. This warrants a critical evaluation of such factors as under-reporting, asymptomatic infections, post kala azar dermal leishmaniasis (PKDL) cases, and drug resistance. In this review, we highlight lesser-understood atypical presentations of the disease involving atypical parasite strains against a background of classical leishmaniasis with a focus on the Indian subcontinent.
METHODS AND FINDINGS
A literature review based on endemic areas, the nature of disease manifestation, and underlying causative parasite was performed with data collected from WHO reports for each country. Searches on PubMed included the term ''leishmaniasis" and "leishmaniasis epidemiology" alone and in combination with each of the endemic countries, Leishmania species, cutaneous, visceral, endemic, non-endemic, typical, classical, atypical, and unusual with no date limit and published in English up to September 2017. Our findings portray a scenario with a wider distribution of the disease in new endemic foci, with new discoveries of parasite-driven atypical disease manifestations in different regions of the world. Unlike the classical picture, some Leishmania species are associated with more than one disease presentation, e.g., the L. donovani complex, generally associated with the visceral form, is now also associated with a cutaneous disease presentation, while L. tropica species complex, known to cause cutaneous disease, can cause viscerotropic disease. This phenomenon points towards the discovery of novel parasite variants as etiologic agents of atypical disease manifestations and represents an excellent opportunity to identify and study genes that control disease virulence and tropism.
CONCLUSIONS
The increased recognition of atypical leishmaniasis as an outcome of parasite variants has major implications for leishmaniasis control and elimination. Identifying molecular correlates of parasite isolates from distinct regions associated with different disease phenotypes is required to understand the current epidemiology of leishmaniasis in regions with atypical disease.
Topics: Asymptomatic Infections; Humans; India; Leishmania; Leishmaniasis, Cutaneous; Leishmaniasis, Visceral
PubMed: 30260957
DOI: 10.1371/journal.pntd.0006659 -
Journal of Preventive Medicine and... Dec 2021The clinical manifestations of COVID-19 are different, which can be attributed to asymptomatic carriers, acute respiratory disease and pneumonia with different...
BACKGROUND
The clinical manifestations of COVID-19 are different, which can be attributed to asymptomatic carriers, acute respiratory disease and pneumonia with different severities. The aim of this study was to compare the epidemiological characteristics and outcomes of COVID-19 in patients with clinical symptoms versus asymptomatic patients.
METHODS
In this retrospective cohort study, the epidemiological characteristics of two groups of patients, with clinical symptoms (n = 38,630) and without clinical symptoms who were definitive cases of COVID-19 (n = 2,327) were investigated in the southwestern of Iran. Chi-square test was used to evaluate the differences between qualitative variables in the two study groups.
RESULTS
Of 40,957 patients with COVID-19, 2,327 (5.68%) were asymptomatic, of whom 1391 (59.77%) were males, 1841 patients (79.11%) had a history of contact with definite or suspected cases of COVID-19. Asymptomatic patients were older than symptomatic cases. Patients with clinical symptoms had higher mortality rate than asymptomatic patients (2.68% in symptomatic patients vs 0% in asymptomatic patients).
CONCLUSION
According to the results of our study, the detected viral load in asymptomatic individuals was similar to that of symptomatic patients, indicating that asymptomatic infections can potentially transmit the disease. Therefore, screening and detection of asymptomatic cases is an important and key measure in prevention and early control of COVID-19 worldwide.
Topics: Asymptomatic Infections; COVID-19; Female; Humans; Male; Retrospective Studies; SARS-CoV-2; Viral Load
PubMed: 35603235
DOI: 10.15167/2421-4248/jpmh2021.62.4.2254 -
Demand for longer quarantine period among common and uncommon COVID-19 infections: a scoping review.Infectious Diseases of Poverty Apr 2021As one of the non-pharmacological interventions to control the transmission of COVID-19, determining the quarantine duration is mainly based on the accurate estimates of... (Review)
Review
BACKGROUND
As one of the non-pharmacological interventions to control the transmission of COVID-19, determining the quarantine duration is mainly based on the accurate estimates of the incubation period. However, patients with coarse information of the exposure date, as well as infections other than the symptomatic, were not taken into account in previously published studies. Thus, by using the statistical method dealing with the interval-censored data, we assessed the quarantine duration for both common and uncommon infections. The latter type includes the presymptomatic, the asymptomatic and the recurrent test positive patients.
METHODS
As of 10 December 2020, information on cases have been collected from the English and Chinese databases, including Pubmed, Google scholar, CNKI (China National Knowledge Infrastructure) and Wanfang. Official websites and medias were also searched as data sources. All data were transformed into doubly interval-censored and the accelerated failure time model was applied. By estimating the incubation period and the time-to-event distribution of worldwide COVID-19 patients, we obtain the large percentiles for determining and suggesting the quarantine policies. For symptomatic and presymptomatic COVID-19 patients, the incubation time is the duration from exposure to symptom onset. For the asymptomatic, we substitute the date of first positive result of nucleic acid testing for that of symptom onset. Furthermore, the time from hospital discharge or getting negative test result to the positive recurrence has been calculated for recurrent positive patients.
RESULTS
A total of 1920 laboratory confirmed COVID-19 cases were included. Among all uncommon infections, 34.1% (n = 55) of them developed symptoms or were identified beyond fourteen days. Based on all collected cases, the 95th and 99th percentiles were estimated to be 16.2 days (95% CI 15.5-17.0) and 22.9 days (21.7‒24.3) respectively. Besides, we got similar estimates based on merely symptomatic and presymptomatic infections as 15.1 days (14.4‒15.7) and 21.1 days (20.0‒22.2).
CONCLUSIONS
There are a certain number of infected people who require longer quarantine duration. Our findings well support the current practice of the extended active monitoring. To further prevent possible transmissions induced and facilitated by such infectious outliers after the 14-days quarantine, properly prolonging the quarantine duration could be prudent for high-risk scenarios and in regions with insufficient test resources.
Topics: Adolescent; Adult; Aged; Asymptomatic Diseases; Asymptomatic Infections; COVID-19; Carrier State; Child; Child, Preschool; Female; Humans; Infant; Infant, Newborn; Infectious Disease Incubation Period; Male; Middle Aged; Models, Statistical; Quarantine; SARS-CoV-2; Time Factors; Young Adult
PubMed: 33902695
DOI: 10.1186/s40249-021-00847-y -
Annals of Internal Medicine May 2021Asymptomatic infection seems to be a notable feature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen that causes coronavirus disease 2019...
BACKGROUND
Asymptomatic infection seems to be a notable feature of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen that causes coronavirus disease 2019 (COVID-19), but the prevalence is uncertain.
PURPOSE
To estimate the proportion of persons infected with SARS-CoV-2 who never develop symptoms.
DATA SOURCES
Searches of Google News, Google Scholar, medRxiv, and PubMed using the keywords , , , , , , and .
STUDY SELECTION
Observational, descriptive studies and reports of mass screening for SARS-CoV-2 that were either cross-sectional or longitudinal in design; were published through 17 November 2020; and involved SARS-CoV-2 nucleic acid or antibody testing of a target population, regardless of current symptomatic status, over a defined period.
DATA EXTRACTION
The authors collaboratively extracted data on the study design, type of testing performed, number of participants, criteria for determining symptomatic status, testing results, and setting.
DATA SYNTHESIS
Sixty-one eligible studies and reports were identified, of which 43 used polymerase chain reaction (PCR) testing of nasopharyngeal swabs to detect current SARS-CoV-2 infection and 18 used antibody testing to detect current or prior infection. In the 14 studies with longitudinal data that reported information on the evolution of symptomatic status, nearly three quarters of persons who tested positive but had no symptoms at the time of testing remained asymptomatic. The highest-quality evidence comes from nationwide, representative serosurveys of England ( = 365 104) and Spain ( = 61 075), which suggest that at least one third of SARS-CoV-2 infections are asymptomatic.
LIMITATION
For PCR-based studies, data are limited to distinguish presymptomatic from asymptomatic infection. Heterogeneity precluded formal quantitative syntheses.
CONCLUSION
Available data suggest that at least one third of SARS-CoV-2 infections are asymptomatic. Longitudinal studies suggest that nearly three quarters of persons who receive a positive PCR test result but have no symptoms at the time of testing will remain asymptomatic. Control strategies for COVID-19 should be altered, taking into account the prevalence and transmission risk of asymptomatic SARS-CoV-2 infection.
PRIMARY FUNDING SOURCE
National Institutes of Health.
Topics: Asymptomatic Infections; COVID-19; Humans; Pandemics; SARS-CoV-2
PubMed: 33481642
DOI: 10.7326/M20-6976 -
MSphere May 2020serovar Newport ( Newport) infections are gradually on the rise in China from the last decade. For humans' infections, Newport has been ranked among the top five...
serovar Newport ( Newport) infections are gradually on the rise in China from the last decade. For humans' infections, Newport has been ranked among the top five serovars responsible for persistent infections, globally. A total of 290 Newport strains with their relevant clinical metadata were analyzed, and the strains were subjected to whole-genome sequence analysis. Among these, 62.4% ( = 181) were from diarrheic patients and 28.9% ( = 84) were from asymptomatic individuals (including adults and youngsters) while 8.6% ( = 25) were from cases of persistent diarrhea in infants (28%, = 7) and toddlers (72%, = 18). The association between the sequence types (STs) and the variations in the clinical presentation was statistically significant (0.0432), with ST46 causing diarrhea or representing asymptomatic patients and ST31 or ST68 causing persistent diarrhea. Genomic analysis revealed that the highest proportion of the isolates (98.5%, = 279), primarily from patients with or without diarrhea rather than from asymptomatic individuals, carried antimicrobial resistance determinants corresponding to the aminoglycosides and beta-lactams, highlighting the need for cautionary usage of antimicrobials in such patients. These findings also suggest that cases of nontyphoidal infection with symptoms of acute diarrhea or persistent diarrhea caused by Newport should be handled with caution, due to the high chance of development of an antimicrobial resistance phenotype that might lead to therapeutic failures. Together, Newport ST31 and ST46, which have the highest frequency of carriage of multidrug resistance, are potentially responsible for antimicrobial-resistant diarrhea/persistent diarrhea in infants and children, while adult humans are more likely to be (asymptomatic) carriers of the Newport strains. Human infections caused by Newport generally lead to gastrointestinal diseases. These infections are normally self-limiting; however, in certain cases, broad-spectrum antimicrobials are prescribed for the treatment. The Chinese National Foodborne Disease Surveillance Network has reported a gradual increase in the incidence of multidrug-resistant Newport infections in humans. After careful evaluation of the dynamic relationship among the clinical findings, the age group, and the genomic sequence data, it was found that young patients represented the major group with persistent diarrhea, whereas adults were either asymptomatic or diarrheic. Furthermore, all these strains contained multiple acquired antimicrobial resistance determinants, which limited the use of antimicrobials for human patients of all age groups. This analysis of the laboratory-confirmed cases, coupled with genetic analysis of the corresponding pathogen, revealed that antimicrobial treatment of persistent infections by Newport in infants and toddlers, and in asymptomatic or diarrheic adults, may not be successful. If the antimicrobials must be prescribed at all, they must be used with caution because of the presence of multiple acquired antimicrobial resistance determinants in such strains.
Topics: Adolescent; Adult; Anti-Bacterial Agents; Asymptomatic Infections; Child; Child, Preschool; China; Diarrhea; Epidemiological Monitoring; Female; Humans; Infant; Microbial Sensitivity Tests; Salmonella Infections; Salmonella enterica; Serogroup; Whole Genome Sequencing; Young Adult
PubMed: 32461269
DOI: 10.1128/mSphere.00163-20