scholarly journals Asymptomatic SARS-CoV-2 infection and the demography of COVID-19

2021 ◽  
Author(s):  
Zengmiao Wang ◽  
Peiyi Wu ◽  
Jingyuan Wang ◽  
Jose Lourenco ◽  
Bingying Li ◽  
...  
Keyword(s):  
Age Distribution ◽  
Geographic Location ◽  
Compartment Model ◽  
Control Measures ◽  
Contact Tracing ◽  
Age Group ◽  
Age Dependent ◽  
Geographic Differences ◽  
Asymptomatic Infections ◽  
Asymptomatic Individuals

Asymptomatic individuals carrying SARS CoV 2 can transmit the virus and contribute to outbreaks of COVID 19, but it is not yet clear how the proportion of asymptomatic infections varies by age and geographic location. Here we use detailed surveillance data gathered during COVID 19 resurgences in six cities of China at the beginning of 2021 to investigate this question. Data were collected by multiple rounds of city wide PCR test with detailed contact tracing, where each patient was monitored for symptoms through the whole course of infection. We find that the proportion of asymptomatic infections declines with age (coefficient =-0.006, P<0.01), falling from 56% in age group 0~9 years to 12% in age group >60 years. Using an age-stratified compartment model, we show that this age-dependent asymptomatic pattern together with the age distribution of overall cases can explain most of the geographic differences in reported asymptomatic proportions. Combined with demography and contact matrices from other countries worldwide, we estimate that a maximum of 22%~55% of SARS CoV 2 infections would come from asymptomatic cases in an uncontrolled epidemic based on asymptomatic proportions in China. Our analysis suggests that flare ups of COVID 19 are likely if only adults are vaccinated and that surveillance and possibly control measures among children will be still needed in the future to contain epidemic resurgence.

scholarly journals Characteristics and management of asymptomatic SARS-CoV-2 infections

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mine Durusu Tanriover ◽  
Anahita Fathi ◽  
Matthias Raspe ◽  
António Grilo Novais ◽  
Oğuz Abdullah Uyaroğlu
Keyword(s):  
Infected Individual ◽  
Real Life ◽  
Signs And Symptoms ◽  
Control Measures ◽  
Contact Tracing ◽  
Infection Prevention And Control ◽  
Viral Loads ◽  
Asymptomatic Infections ◽  
Prevention And Control Measures ◽  
Asymptomatic Individuals

Abstract The coronavirus disease 2019 (COVID-19) pandemic has caused and is still causing tremendous morbidity, mortality, and damage to our societies. The disease course of COVID-19 can be unpredictable ranging from asymptomatic infections to multi-organ failure and death. Transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) from an asymptomatic infected individual to others has been observed early in the pandemic. Asymptomatic individuals have been shown to have quantitative SARS-CoV-2 viral loads, there may or may not be radiological and/or laboratory abnormalities. No antiviral therapy has been approved for the treatment of asymptomatic SARS-CoV2- infection. The management of asymptomatic individuals at home requires that the person can be monitored for any signs and symptoms of deterioration and that the requirements for infection prevention and control measures can be fulfilled. It is crucial to properly diagnose and manage asymptomatic COVID-19 cases with effective testing, contact tracing, quarantine, and isolation strategies. Preventing asymptomatic SARS-CoV-2 infections that have a major role in the unhindered transmission of the virus is a milestone to take control of the pandemic. Vaccination has been proven to be the crucial pillar for preventing asymptomatic infections and real-life data will continue to exhibit the effects of community vaccination in breaking the transmission chain of SARS-CoV-2 infections.

scholarly journals The contribution of asymptomatic SARS-CoV-2 infections to transmission on the Diamond Princess cruise ship

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Jon C Emery ◽  
Timothy W Russell ◽  
Yang Liu ◽  
Joel Hellewell ◽  
Carl AB Pearson ◽  
...  
Keyword(s):  
Reproduction Number ◽  
Disease Onset ◽  
Control Measures ◽  
Transmission Model ◽  
Cruise Ship ◽  
Transmission Control ◽  
Asymptomatic Infections ◽  
Potential Impact ◽  
Asymptomatic Individuals ◽  
Net Reproduction

A key unknown for SARS-CoV-2 is how asymptomatic infections contribute to transmission. We used a transmission model with asymptomatic and presymptomatic states, calibrated to data on disease onset and test frequency from the Diamond Princess cruise ship outbreak, to quantify the contribution of asymptomatic infections to transmission. The model estimated that 74% (70–78%, 95% posterior interval) of infections proceeded asymptomatically. Despite intense testing, 53% (51–56%) of infections remained undetected, most of them asymptomatic. Asymptomatic individuals were the source for 69% (20–85%) of all infections. The data did not allow identification of the infectiousness of asymptomatic infections, however low ranges (0–25%) required a net reproduction number for individuals progressing through presymptomatic and symptomatic stages of at least 15. Asymptomatic SARS-CoV-2 infections may contribute substantially to transmission. Control measures, and models projecting their potential impact, need to look beyond the symptomatic cases if they are to understand and address ongoing transmission.

scholarly journals Description of measles D4-Hamburg outbreak in Hamburg, Germany, December 2008 to June 2009, which disproportionally affected a local Roma community

2012 ◽  
Vol 17 (24) ◽  
Author(s):  
G Hegasy ◽  
K Kätzner ◽  
M Helle ◽  
A Mankertz ◽  
S Baumgarte ◽  
...  
Keyword(s):  
Influencing Factors ◽  
Age Distribution ◽  
Control Measures ◽  
European Countries ◽  
Federal State ◽  
Age Group ◽  
Measles Outbreak ◽  
Stratified Analysis ◽  
Epidemiological Characteristics

From December 2008 to June 2009 a measles outbreak occurred in the Federal State of Hamburg, Germany. The outbreak affected 216 persons and was caused by a new measles strain termed D4-Hamburg which led to consecutive outbreaks between 2009 and 2011 in at least 12 European countries. Here, we describe epidemiological characteristics of the outbreak and evaluate the control measures taken in Hamburg. In one of the seven boroughs of Hamburg a local Roma community comprised more than 50% of the notified cases. We compared in a stratified analysis the age distribution of these cases with cases of fellow citizens who did not belong to the Roma community. The age group of infants (0-11 months) comprised 33% among the non-Roma measles cases, while in the Roma community only 4% belonged to this stratum. In the stratum of 5-17 year-olds only 8% were affected among the non-Roma cases, whereas in the Roma community 50% belonged to this age group. We discuss the influencing factors that might have led to this difference in age distribution between the two groups.

scholarly journals The contribution of asymptomatic SARS-CoV-2 infections to transmission - a model-based analysis of the Diamond Princess outbreak

2020 ◽  
Author(s):  
Jon C Emery ◽  
Timothy W Russell ◽  
Yang Liu ◽  
Joel Hellewell ◽  
Carl AB Pearson ◽  
...  
Keyword(s):  
Control Measures ◽  
Transmission Model ◽  
Cruise Ship ◽  
Symptomatic Disease ◽  
Transmission Data ◽  
Asymptomatic Infections ◽  
Using Data ◽  
Asymptomatic Individuals ◽  
Net Reproduction ◽  
Model Based Analysis

AbstractBackgroundSome key gaps in the understanding of SARS-CoV-2 infection remain. One of them is the contribution to transmission from individuals experiencing asymptomatic infections. We aimed to characterise the proportion and infectiousness of asymptomatic infections using data from the outbreak on the Diamond Princess cruise ship.MethodsWe used a transmission model of COVID-19 with asymptomatic and presymptomatic states calibrated to outbreak data from the Diamond Princess, to quantify the contribution of asymptomatic infections to transmission. Data available included the date of symptom onset for symptomatic disease for passengers and crew, the number of symptom agnostic tests done each day, and date of positive test for asymptomatic and presymptomatic individuals.FindingsOn the Diamond Princess 74% (70-78%) of infections proceeded asymptomatically, i.e. a 1:3.8 case-to-infection ratio. Despite the intense testing 53%, (51-56%) of infections remained undetected, most of them asymptomatic. Asymptomatic individuals were the source for 69% (20-85%) of all infections. While the data did not allow identification of the infectiousness of asymptomatic infections, assuming no or low infectiousness resulted in posterior estimates for the net reproduction number of an individual progressing through presymptomatic and symptomatic stages in excess of 15.InterpretationAsymptomatic SARS-CoV-2 infections may contribute substantially to transmission. This is essential to consider for countries when assessing the potential effectiveness of ongoing control measures to contain COVID-19.FundingERC Starting Grant (#757699), Wellcome trust (208812/Z/17/Z), HDR UK (MR/S003975/1)

scholarly journals Increased investment in gametocytes in asymptomatic Plasmodium falciparum infections in the wet season

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Colins O. Oduma ◽  
Sidney Ogolla ◽  
Harrysone Atieli ◽  
Bartholomew N. Ondigo ◽  
Ming-Chieh Lee ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Limit Of Detection ◽  
Parasite Prevalence ◽  
Dry Season ◽  
Control Measures ◽  
Wet Season ◽  
Western Kenya ◽  
Vector Abundance ◽  
Asymptomatic Infections ◽  
Asymptomatic Individuals

Abstract Background Transmission stemming from asymptomatic infections is increasingly being recognized as a threat to malaria elimination. In many regions, malaria transmission is seasonal. It is not well understood whether Plasmodium falciparum modulates its investment in transmission to coincide with seasonal vector abundance. Methods We sampled 1116 asymptomatic individuals in the wet season, when vectors are abundant, and 1743 in the dry season, in two sites in western Kenya, representing different transmission intensities (Chulaimbo, moderate transmission, and Homa Bay, low transmission). Blood samples were screened for P. falciparum by qPCR, and gametocytes by pfs25 RT-qPCR. Results Parasite prevalence by qPCR was 27.1% (Chulaimbo, dry), 48.2% (Chulaimbo, wet), 9.4% (Homabay, dry), and 7.8% (Homabay, wet). Mean parasite densities did not differ between seasons (P = 0.562). pfs25 transcripts were detected in 119/456 (26.1%) of infections. In the wet season, fewer infections harbored detectable gametocytes (22.3% vs. 33.8%, P = 0.009), but densities were 3-fold higher (wet: 3.46 transcripts/uL, dry: 1.05 transcripts/uL, P < 0.001). In the dry season, 4.0% of infections carried gametocytes at moderate-to-high densities likely infective (> 1 gametocyte per 2 uL blood), compared to 7.9% in the wet season. Children aged 5–15 years harbored 76.7% of infections with gametocytes at moderate-to-high densities. Conclusions Parasites increase their investment in transmission in the wet season, reflected by higher gametocyte densities. Despite increased gametocyte densities, parasite density remained similar across seasons and were often below the limit of detection of microscopy or rapid diagnostic test, thus a large proportion of infective infections would escape population screening in the wet season. Seasonal changes of gametocytemia in asymptomatic infections need to be considered when designing malaria control measures.

scholarly journals Suppression of COVID-19 outbreak in the municipality of Vo’, Italy

2020 ◽  
Author(s):  
Enrico Lavezzo ◽  
Elisa Franchin ◽  
Constanze Ciavarella ◽  
Gina Cuomo-Dannenburg ◽  
Luisa Barzon ◽  
...  
Keyword(s):  
Viral Load ◽  
Control Measures ◽  
Contact Tracing ◽  
Contact Network ◽  
Threshold Data ◽  
Serial Interval ◽  
Significant Difference ◽  
Consecutive Time ◽  
Asymptomatic Infections ◽  
Regional Authorities

AbstractOn the 21st of February 2020 a resident of the municipality of Vo’, a small town near Padua, died of pneumonia due to SARS-CoV-2 infection1. This was the first COVID-19 death detected in Italy since the emergence of SARS-CoV-2 in the Chinese city of Wuhan, Hubei province2. In response, the regional authorities imposed the lockdown of the whole municipality for 14 days3. We collected information on the demography, clinical presentation, hospitalization, contact network and presence of SARS-CoV-2 infection in nasopharyngeal swabs for 85.9% and 71.5% of the population of Vo’ at two consecutive time points. On the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI) 2.1-3.3%). On the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI 0.8-1.8%). Notably, 43.2% (95% CI 32.2-54.7%) of the confirmed SARS-CoV-2 infections detected across the two surveys were asymptomatic. The mean serial interval was 6.9 days (95% CI 2.6-13.4). We found no statistically significant difference in the viral load (as measured by genome equivalents inferred from cycle threshold data) of symptomatic versus asymptomatic infections (p-values 0.6 and 0.2 for E and RdRp genes, respectively, Exact Wilcoxon-Mann-Whitney test). Contact tracing of the newly infected cases and transmission chain reconstruction revealed that most new infections in the second survey were infected in the community before the lockdown or from asymptomatic infections living in the same household. This study sheds new light on the frequency of asymptomatic SARS-CoV-2 infection and their infectivity (as measured by the viral load) and provides new insights into its transmission dynamics, the duration of viral load detectability and the efficacy of the implemented control measures.

scholarly journals Re-emergence of Invasive Pneumococcal Disease in Germany during the Spring and Summer of 2021

2021 ◽  
Author(s):  
Stephanie R Perniciaro ◽  
Mark PG van der Linden ◽  
Daniel M Weinberger
Keyword(s):  
Invasive Pneumococcal Disease ◽  
Pneumococcal Disease ◽  
Age Distribution ◽  
Geographic Location ◽  
Surveillance Data ◽  
Age Group ◽  
Percent Change ◽  
Mobility Data ◽  
Baseline Values ◽  
Pharmaceutical Interventions

Abstract Background: The incidence of invasive pneumococcal disease (IPD) decreased worldwide in 2020 and the first quarter of 2021, concurrent with non-pharmaceutical interventions (NPIs) intended to stymie transmission of SARS-CoV-2. In 2021, stringency of these NPI strategies has varied. We investigated age- and serotype-specific variations in IPD case counts in Germany in 2020-2021. Methods: IPD cases through July 31, 2021 were stratified by age group, serotype, or geographic location. IPD surveillance data in 2020-2021 were compared with: 1) IPD surveillance data from 2015-2019, 2) mobility data during 2020 and 2021, and 3) NPI stringency data in 2020 and 2021. Results: IPD began to return towards baseline values among children 0 to 4 years old in April 2021 and exceeded baseline levels by June 2021 (a 9% increase over the average monthly values for 2015-2019). Children 5 to 14, adults aged 15-34 and adults 80 years and older showed increases in IPD cases which went over baseline values starting in July 2021, with increases also starting in Spring 2021. The age distribution and proportion of vaccine serotype IPD remained comparable to previous years despite lower overall case counts in 2020 and 2021. The percent change in IPD incidence compared to the previous five years correlated with changes in mobility and with NPI stringency. Conclusions: IPD levels began to return to and exceed seasonal levels in Spring/Summer 2021 in Germany following sharp declines in 2020 that coincided with NPIs related to the COVID-19 pandemic. Proportions of vaccine serotypes remained largely consistent throughout 2020-2021.

An Epidemiological Analysis of COVID-19 Confirmed Cases, Reported at National Institute of Health, Pakistan (Preprint)

2020 ◽  
Author(s):  
Ambreen Chaudhry
Keyword(s):  
Age Groups ◽  
Target Population ◽  
Control Measures ◽  
Contact Tracing ◽  
Bivariate Analysis ◽  
Travel History ◽  
Disease Epidemiology ◽  
Hygiene Practices ◽  
Multi Center Study ◽  
Epidemiological Characteristics

BACKGROUND Coronavirus disease (Covid-19) is a zoonotic disease of novel origin that posed a continuous threat to health worldwide after taking the shape of the pandemic. An understanding of disease epidemiology is supportive in timely preventive and control measures as well as contact tracing and curbing surveillance activities. OBJECTIVE The objective of our study was to determine the epidemiological characteristics of COVID-19 confirmed cases reported at the National Institute of Health Pakistan and elements of its spread in Pakistan. METHODS A retrospective record review was conducted at the National Institute of Health (NIH) Islamabad, Pakistan from January 25 to April 4, 2020. Univariate and bivariate analysis was done with 95% CI and p<0.05. RESULTS A total of 14,422 samples of suspected COVID-19 cases were received with a positivity rate of 9% (n=1348). Among all 70% (n=939) were male. The median age was 41years of age (range: 01-99Years). Among all, 19% were from 30-39 years old followed by 50-59 years old (17%). Children remained the least affected by 3% (n=35). Of the total reported cases, 55% (n=735) have reported the travel history within the last 14 days. Among these travelers’ international travelers were 23% (n=166) and domestic travelers were 77% (n=569). Travel history including both international and domestic remained significantly associated with the different age groups and Young adults remained more vulnerable to COVID-19 (P=0.03). Fever, SOB, and Cough remained the most significantly associated (P<0.05) in all age groups. CONCLUSIONS A higher incidence of COVID-19 among elderly men suggests robust quarantine measures for this target population. An escalating incidence of local transmission needs strict social distancing and hygiene practices to help flatten the curve. An extensive multi-center study is also recommended for a full understanding of disease dynamics.

scholarly journals Countries with delayed COVID-19 introduction – characteristics, drivers, gaps, and opportunities

2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Zheng Li ◽  
Cynthia Jones ◽  
Girum S. Ejigu ◽  
Nisha George ◽  
Amanda L. Geller ◽  
...  
Keyword(s):  
Geographic Location ◽  
Control Measures ◽  
World Health ◽  
Small Island ◽  
Influenza Surveillance ◽  
Middle Income ◽  
School Closing ◽  
Travel Restrictions ◽  
Potential Factors ◽  
Health Organization

Abstract Background Three months after the first reported cases, COVID-19 had spread to nearly 90% of World Health Organization (WHO) member states and only 24 countries had not reported cases as of 30 March 2020. This analysis aimed to 1) assess characteristics, capability to detect and monitor COVID-19, and disease control measures in these 24 countries, 2) understand potential factors for the reported delayed COVID-19 introduction, and 3) identify gaps and opportunities for outbreak preparedness, particularly in low and middle-income countries (LMICs). We collected and analyzed publicly available information on country characteristics, COVID-19 testing, influenza surveillance, border measures, and preparedness activities in these countries. We also assessed the association between the temporal spread of COVID-19 in all countries with reported cases with globalization indicator and geographic location. Results Temporal spreading of COVID-19 was strongly associated with countries’ globalization indicator and geographic location. Most of the 24 countries with delayed COVID-19 introduction were LMICs; 88% were small island or landlocked developing countries. As of 30 March 2020, only 38% of these countries reported in-country COVID-19 testing capability, and 71% reported conducting influenza surveillance during the past year. All had implemented two or more border measures, (e.g., travel restrictions and border closures) and multiple preparedness activities (e.g., national preparedness plans and school closing). Conclusions Limited testing capacity suggests that most of the 24 delayed countries may have lacked the capability to detect and identify cases early through sentinel and case-based surveillance. Low global connectedness, geographic isolation, and border measures were common among these countries and may have contributed to the delayed introduction of COVID-19 into these countries. This paper contributes to identifying opportunities for pandemic preparedness, such as increasing disease detection, surveillance, and international collaborations. As the global situation continues to evolve, it is essential for countries to improve and prioritize their capacities to rapidly prevent, detect, and respond, not only for COVID-19, but also for future outbreaks.

scholarly journals Relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals: a rapid scoping review

BMJ Open ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. e042354
Author(s):  
David McEvoy ◽  
Conor McAloon ◽  
Aine Collins ◽  
Kevin Hunt ◽  
Francis Butler ◽  
...  
Keyword(s):  
Scoping Review ◽  
Quantitative Measure ◽  
Contact Tracing ◽  
Cochrane Library ◽  
International Studies ◽  
Screening Process ◽  
Modelling Studies ◽  
Asymptomatic Individuals ◽  
Definition Of ◽  
The Cochrane Library

ObjectivesThe aim of this study was to determine the relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals based on a scoping review of available literature.DesignRapid scoping review of peer-reviewed literature from 1 January to 5 December 2020 using the LitCovid database and the Cochrane library.SettingInternational studies on the infectiousness of individuals infected with SARS-CoV-2.ParticipantsStudies were selected for inclusion if they defined asymptomatics as a separate cohort distinct from presymptomatics and if they provided a quantitative measure of the infectiousness of asymptomatics relative to symptomatics.Primary outcome measuresPCR result (PCR studies), the rate of infection (mathematical modelling studies) and secondary attack rate (contact tracing studies) - in each case from asymptomatic in comparison with symptomatic individuals.ResultsThere are only a limited number of published studies that report estimates of relative infectiousness of asymptomatic compared with symptomatic individuals. 12 studies were included after the screening process. Significant differences exist in the definition of infectiousness. PCR studies in general show no difference in shedding levels between symptomatic and asymptomatic individuals; however, the number of study subjects is generally limited. Two modelling studies estimate relative infectiousness to be 0.43 and 0.57, but both of these were more reflective of the infectiousness of undocumented rather than asymptomatic cases. The results from contact tracing studies include estimates of relative infectiousness of 0, but with insufficient evidence to conclude that it is significantly different from 1.ConclusionsThere is considerable heterogeneity in estimates of relative infectiousness highlighting the need for further investigation of this important parameter. It is not possible to provide any conclusive estimate of relative infectiousness, as the estimates from the reviewed studies varied between 0 and 1.

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