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1.
mSphere ; 5(3)2020 06 24.
Article in English | MEDLINE | ID: covidwho-2193484

ABSTRACT

The contamination of patients' surroundings by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains understudied. We sampled the surroundings and the air of six negative-pressure non-intensive care unit (non-ICU) rooms in a designated isolation ward in Chengdu, China, that were occupied by 13 laboratory-confirmed coronavirus disease 2019 (COVID-19) patients who had returned from overseas travel, including 2 asymptomatic patients. A total of 44 of 112 (39.3%) surface samples were positive for SARS-CoV-2 as detected by real-time PCR, suggesting extensive contamination, although all of the air samples were negative. In particular, in a single room occupied by an asymptomatic patient, four sites were SARS-CoV-2 positive, highlighting that asymptomatic COVID-19 patients do contaminate their surroundings and impose risks for others with close contact. Placement of COVID-19 patients in rooms with negative pressure may bring a false feeling of safety, and the importance of rigorous environment cleaning should be emphasized.IMPORTANCE Although it has been well recognized that the virus SARS-CoV-2, the causative agent of COVID-19, can be acquired by exposure to fomites, surprisingly, the contamination of patients' surroundings by SARS-CoV-2 is largely unknown, as there have been few studies. We performed an environmental sampling study for 13 laboratory-confirmed COVID-19 patients and found extensive contamination of patients' surroundings. In particular, we found that asymptomatic COVID-19 patients contaminated their surroundings and therefore imposed risks for other people. Environment cleaning should be emphasized in negative-pressure rooms. The findings may be useful to guide infection control practice to protect health care workers.


Subject(s)
Asymptomatic Infections/epidemiology , Betacoronavirus/isolation & purification , Coronavirus Infections/epidemiology , Environmental Exposure , Environmental Microbiology , Pneumonia, Viral/epidemiology , COVID-19 , Containment of Biohazards/methods , Coronavirus Infections/pathology , Environment , Humans , Pandemics , Pneumonia, Viral/pathology , SARS-CoV-2
2.
Elife ; 92020 08 21.
Article in English | MEDLINE | ID: covidwho-2155740

ABSTRACT

We conducted voluntary Covid-19 testing programmes for symptomatic and asymptomatic staff at a UK teaching hospital using naso-/oro-pharyngeal PCR testing and immunoassays for IgG antibodies. 1128/10,034 (11.2%) staff had evidence of Covid-19 at some time. Using questionnaire data provided on potential risk-factors, staff with a confirmed household contact were at greatest risk (adjusted odds ratio [aOR] 4.82 [95%CI 3.45-6.72]). Higher rates of Covid-19 were seen in staff working in Covid-19-facing areas (22.6% vs. 8.6% elsewhere) (aOR 2.47 [1.99-3.08]). Controlling for Covid-19-facing status, risks were heterogenous across the hospital, with higher rates in acute medicine (1.52 [1.07-2.16]) and sporadic outbreaks in areas with few or no Covid-19 patients. Covid-19 intensive care unit staff were relatively protected (0.44 [0.28-0.69]), likely by a bundle of PPE-related measures. Positive results were more likely in Black (1.66 [1.25-2.21]) and Asian (1.51 [1.28-1.77]) staff, independent of role or working location, and in porters and cleaners (2.06 [1.34-3.15]).


Subject(s)
Coronavirus Infections/epidemiology , Health Personnel/statistics & numerical data , Pneumonia, Viral/epidemiology , Adolescent , Adult , Age Factors , Aged , Asymptomatic Infections/epidemiology , Betacoronavirus/isolation & purification , COVID-19 , Coronavirus Infections/transmission , Coronavirus Infections/virology , Female , Hospitals, Teaching/statistics & numerical data , Humans , Incidence , Infectious Disease Transmission, Patient-to-Professional/statistics & numerical data , Intensive Care Units/statistics & numerical data , Male , Middle Aged , Pandemics , Pneumonia, Viral/transmission , Pneumonia, Viral/virology , Risk , SARS-CoV-2 , Surveys and Questionnaires , United Kingdom/epidemiology , Young Adult
3.
Front Immunol ; 13: 959697, 2022.
Article in English | MEDLINE | ID: covidwho-2141992

ABSTRACT

Malaria has been hypothesized as a factor that may have reduced the severity of the COVID-19 pandemic in sub-Saharan Africa. To evaluate the effect of recent malaria on COVID-19 we assessed a subgroup of individuals participating in a longitudinal cohort COVID-19 serosurvey that were also undergoing intensive malaria monitoring as part of antimalarial vaccine trials during the 2020 transmission season in Mali. These communities experienced a high incidence of primarily asymptomatic or mild COVID-19 during 2020 and 2021. In 1314 individuals, 711 were parasitemic during the 2020 malaria transmission season; 442 were symptomatic with clinical malaria and 269 had asymptomatic infection. Presence of parasitemia was not associated with new COVID-19 seroconversion (29.7% (211/711) vs. 30.0% (181/603), p=0.9038) or with rates of reported symptomatic seroconversion during the malaria transmission season. In the subsequent dry season, prior parasitemia was not associated with new COVID-19 seroconversion (30.2% (133/441) vs. 31.2% (108/346), p=0.7499), with symptomatic seroconversion, or with reversion from seropositive to seronegative (prior parasitemia: 36.2% (64/177) vs. no parasitemia: 30.1% (37/119), p=0.3842). After excluding participants with asymptomatic infection, clinical malaria was also not associated with COVID-19 serostatus or symptomatic seroconversion when compared to participants with no parasitemia during the monitoring period. In communities with intense seasonal malaria and a high incidence of asymptomatic or mild COVID-19, we did not demonstrate a relationship between recent malaria and subsequent response to COVID-19. Lifetime exposure, rather than recent infection, may be responsible for any effect of malaria on COVID-19 severity.


Subject(s)
COVID-19 , Malaria , Antibody Formation , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , Humans , Malaria/epidemiology , Mali/epidemiology , Pandemics , Parasitemia/epidemiology
7.
Intern Med ; 61(20): 3053-3062, 2022 Oct 15.
Article in English | MEDLINE | ID: covidwho-2079926

ABSTRACT

Objective To examine the continuation of antibody prevalence status after 12 months and background factors in antibody-positive subjects following asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods We initially determined the SARS-CoV-2 anti-nucleocapsid protein immunoglobulin G (anti-N IgG) antibody prevalence in 1,603 patients, doctors, and nurses at 65 medical institutions in Kanagawa Prefecture, Japan. We then obtained consent from 33 of the 39 subjects who tested positive and performed follow-up for 12 months. Results Follow-up for up to 12 months showed that a long-term response of the anti-N IgG antibody could be detected in 6 of the 33 participants (18.2%). The proportions with hypertension, using an angiotensin-receptor blocker, and without a drinking habit were higher among the participants with a long-term anti-N IgG antibody response for up to 12 months than among those without a long-term antibody response. Conclusions The proportion of individuals with subclinical COVID-19 who continuously had a positive result for the anti-N IgG antibody at 12 months was low.


Subject(s)
COVID-19 , Immunoglobulin G , Angiotensin Receptor Antagonists , Antibodies, Viral/blood , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , COVID-19/immunology , Coronavirus Nucleocapsid Proteins/immunology , Humans , Immunoglobulin G/blood , Phosphoproteins/immunology , SARS-CoV-2
8.
JAMA ; 328(15): 1523-1533, 2022 10 18.
Article in English | MEDLINE | ID: covidwho-2074838

ABSTRACT

Importance: Data on the epidemiology of mild to moderately severe COVID-19 are needed to inform public health guidance. Objective: To evaluate associations between 2 or 3 doses of mRNA COVID-19 vaccine and attenuation of symptoms and viral RNA load across SARS-CoV-2 viral lineages. Design, Setting, and Participants: A prospective cohort study of essential and frontline workers in Arizona, Florida, Minnesota, Oregon, Texas, and Utah with COVID-19 infection confirmed by reverse transcriptase-polymerase chain reaction testing and lineage classified by whole genome sequencing of specimens self-collected weekly and at COVID-19 illness symptom onset. This analysis was conducted among 1199 participants with SARS-CoV-2 from December 14, 2020, to April 19, 2022, with follow-up until May 9, 2022, reported. Exposures: SARS-CoV-2 lineage (origin strain, Delta variant, Omicron variant) and COVID-19 vaccination status. Main Outcomes and Measures: Clinical outcomes included presence of symptoms, specific symptoms (including fever or chills), illness duration, and medical care seeking. Virologic outcomes included viral load by quantitative reverse transcriptase-polymerase chain reaction testing along with viral viability. Results: Among 1199 participants with COVID-19 infection (714 [59.5%] women; median age, 41 years), 14.0% were infected with the origin strain, 24.0% with the Delta variant, and 62.0% with the Omicron variant. Participants vaccinated with the second vaccine dose 14 to 149 days before Delta infection were significantly less likely to be symptomatic compared with unvaccinated participants (21/27 [77.8%] vs 74/77 [96.1%]; OR, 0.13 [95% CI, 0-0.6]) and, when symptomatic, those vaccinated with the third dose 7 to 149 days before infection were significantly less likely to report fever or chills (5/13 [38.5%] vs 62/73 [84.9%]; OR, 0.07 [95% CI, 0.0-0.3]) and reported significantly fewer days of symptoms (10.2 vs 16.4; difference, -6.1 [95% CI, -11.8 to -0.4] days). Among those with Omicron infection, the risk of symptomatic infection did not differ significantly for the 2-dose vaccination status vs unvaccinated status and was significantly higher for the 3-dose recipients vs those who were unvaccinated (327/370 [88.4%] vs 85/107 [79.4%]; OR, 2.0 [95% CI, 1.1-3.5]). Among symptomatic Omicron infections, those vaccinated with the third dose 7 to 149 days before infection compared with those who were unvaccinated were significantly less likely to report fever or chills (160/311 [51.5%] vs 64/81 [79.0%]; OR, 0.25 [95% CI, 0.1-0.5]) or seek medical care (45/308 [14.6%] vs 20/81 [24.7%]; OR, 0.45 [95% CI, 0.2-0.9]). Participants with Delta and Omicron infections who received the second dose 14 to 149 days before infection had a significantly lower mean viral load compared with unvaccinated participants (3 vs 4.1 log10 copies/µL; difference, -1.0 [95% CI, -1.7 to -0.2] for Delta and 2.8 vs 3.5 log10 copies/µL, difference, -1.0 [95% CI, -1.7 to -0.3] for Omicron). Conclusions and Relevance: In a cohort of US essential and frontline workers with SARS-CoV-2 infections, recent vaccination with 2 or 3 mRNA vaccine doses less than 150 days before infection with Delta or Omicron variants, compared with being unvaccinated, was associated with attenuated symptoms, duration of illness, medical care seeking, or viral load for some comparisons, although the precision and statistical significance of specific estimates varied.


Subject(s)
COVID-19 Vaccines , COVID-19 , Vaccination , Viral Load , Adult , Female , Humans , Male , COVID-19/diagnosis , COVID-19/genetics , COVID-19/prevention & control , COVID-19/virology , COVID-19 Vaccines/administration & dosage , COVID-19 Vaccines/therapeutic use , Prospective Studies , RNA, Viral/analysis , RNA, Viral/genetics , RNA-Directed DNA Polymerase , SARS-CoV-2/genetics , Vaccination/statistics & numerical data , United States/epidemiology , Viral Load/drug effects , Viral Load/genetics , Viral Load/statistics & numerical data , Whole Genome Sequencing , Asymptomatic Infections/epidemiology , Asymptomatic Infections/therapy , Time Factors , Patient Acceptance of Health Care/statistics & numerical data
9.
Infect Dis Poverty ; 11(1): 94, 2022 Sep 05.
Article in English | MEDLINE | ID: covidwho-2009471

ABSTRACT

BACKGROUND: A significant decline in malaria burden was documented in previously high burden African countries. Even though the global decline in malaria burden is significant, about 95% of it was typically found in 29 African countries and the decline was affected by COVID-19 in 2020. The considerable reduction in malaria incidence was noted due to effective prevention and treatment efforts, and rapid changes in living conditions. The relationship between the occurrence of asymptomatic malaria infection and household living conditions is well unstudied. This study aimed to determine the association between household living conditions and the occurrence of asymptomatic malaria in the lowlands of Ethiopia. METHODS: A community-based cross-sectional study was conducted from January to March 2021 in twelve villages of Gambella, Southern Nation Nationalities and People Region and Afar in Ethiopia. A total of 1366 households were randomly selected, interviewed, and tested for malaria by rapid diagnostic test and blood film microscopic examination. Multiple logistic regression model was used to determine the independent association between living conditions and asymptomatic malaria infection. RESULTS: The prevalence of asymptomatic malaria infection among individuals living in dwellings built with traditional floor/wall/roof ranges from 8.1% to 8.4% while it ranges from 2.0% to 4.6% among those living in modern floor/wall/roof houses. Dwellings built with traditional wall materials (P = 0.050), spending nights with cattle in the same house (P < 0.001), and availability of kitchen in the main house with no partition (P = 0.004) were significantly associated with asymptomatic malaria infection. CONCLUSIONS: Asymptomatic malaria infection was 4.3 times higher among occupants residing in dwellings built with traditional wall materials; 5.6 times higher among households spending nights with cattle in the same house, and 2.3 times higher among households with kitchen in the main house with no partition. Therefore, policies and strategies on malaria elimination need to address or target improvements of the above listed living conditions for the community. A multi sectoral action is required to use these social determinants as a vector control strategic addition; and malaria elimination programs are expected to coordinate the implementation.


Subject(s)
COVID-19 , Malaria , Animals , Asymptomatic Infections/epidemiology , Cattle , Cross-Sectional Studies , Ethiopia/epidemiology , Humans , Malaria/epidemiology , Malaria/prevention & control , Prevalence , Social Conditions
10.
J Med Virol ; 94(12): 5790-5801, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-2003625

ABSTRACT

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.


Subject(s)
Asymptomatic Infections , COVID-19 , Adolescent , Aged , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , Child , China , Humans , SARS-CoV-2
11.
PLoS One ; 17(1): e0252994, 2022.
Article in English | MEDLINE | ID: covidwho-1997319

ABSTRACT

The global impact of coronavirus disease 2019 (COVID-19) is unprecedented, and many control and prevention measures have been implemented to test for and trace COVID-19. However, invisible-spreaders, who are associated with nucleic acid detection and asymptomatic infections, have received insufficient attention in the current COVID-19 control efforts. In this paper, we analyze the time series infection data for Italy, Germany, Brazil, India and Sweden since the first wave outbreak to address the following issues through a series of experiments. We conclude that: 1) As of June 1, 2020, the proportion of invisible-spreaders is close to 0.4% in Sweden, 0.8% in early Italy and Germany, and 0.4% in the middle and late stages. However, in Brazil and India, the proportion still shows a gradual upward trend; 2) During the spread of this pandemic, even a slight increase in the proportion of invisible-spreaders could have large implications for the health of the community; and 3) On resuming work, the pandemic intervention measures will be relaxed, and invisible-spreaders will cause a new round of outbreaks.


Subject(s)
Asymptomatic Infections/epidemiology , COVID-19/transmission , Brazil/epidemiology , COVID-19/diagnosis , COVID-19/epidemiology , COVID-19/virology , Germany/epidemiology , Humans , India/epidemiology , Italy/epidemiology , Models, Theoretical , Pandemics , SARS-CoV-2/isolation & purification , Sweden/epidemiology
12.
Lancet Infect Dis ; 22(8): 1163-1171, 2022 08.
Article in English | MEDLINE | ID: covidwho-1972392

ABSTRACT

BACKGROUND: Whether or not individuals with pauci-symptomatic or asymptomatic Ebola virus infection and unrecognised Ebola virus disease develop clinical sequelae is unknown. We assessed current symptoms and physical examination findings among individuals with pauci-symptomatic or asymptomatic infection and unrecognised Ebola virus disease compared with Ebola virus disease survivors and uninfected contacts. METHODS: Between June 17, 2015, and June 30, 2017, we studied a cohort of Ebola virus disease survivors and their contacts in Liberia. Surveys, current symptoms and physical examination findings, and serology were used to characterise disease status of reported Ebola virus disease, unrecognised Ebola virus disease, pauci-symptomatic or asymptomatic Ebola virus infection, or no infection. We pre-specified findings known to be differentially prevalent among Ebola virus disease survivors versus their contacts (urinary frequency, headache, fatigue, muscle pain, memory loss, joint pain, neurological findings, chest findings, muscle findings, joint findings, abdominal findings, and uveitis). We estimated the prevalence and incidence of selected clinical findings by disease status. FINDINGS: Our analytical cohort included 991 reported Ebola virus disease survivors and 2688 close contacts. The median time from acute Ebola virus disease onset to baseline was 317 days (IQR 271-366). Of 222 seropositive contacts, 115 had pauci-symptomatic or asymptomatic Ebola virus infection and 107 had unrecognised Ebola virus disease. At baseline, prevalent findings of joint pain, memory loss, muscle pain, and fatigue were lowest among those with pauci-symptomatic or asymptomatic infection or no infection, higher among contacts with unrecognised Ebola virus disease, and highest in reported survivors of Ebola virus disease. Joint pain was the most prevalent finding, and was reported in 434 (18%) of 2466 individuals with no infection, 14 (12%) of 115 with pauci-symptomatic or asymptomatic infection, 31 (29%) of 107 with unrecognised Ebola virus disease, and 476 (48%) of 991 with reported Ebola virus disease. In adjusted analyses, this pattern remained for joint pain and memory loss. Survivors had an increased odds of joint pain compared with unrecognised Ebola virus disease contacts (adjusted odds ratio [OR] 2·13, 95% CI 1·34-3·39); unrecognised Ebola virus disease contacts had an increased odds of joint pain compared with those with pauci-symptomatic or asymptomatic infection and uninfected contacts (adjusted OR 1·89, 95% CI 1·21-2·97). The adjusted odds of memory loss was more than four-times higher among survivors than among unrecognised Ebola virus disease contacts (adjusted OR 4·47, 95% CI 2·41-8·30) and two-times higher among unrecognised Ebola virus disease contacts than in those with pauci-symptomatic or asymptomatic infection and uninfected contacts (adjusted OR 2·05, 95% CI 1·10-3·84). By 12 months, prevalent findings had decreased in the three infected groups. INTERPRETATION: Our findings provide evidence of post-Ebola virus disease clinical sequelae among contacts with unrecognised Ebola virus disease but not in people with pauci-symptomatic or asymptomatic Ebola virus infection. FUNDING: National Cancer Institute and National Institute of Allergy and Infectious Diseases of the National Institutes of Health.


Subject(s)
Ebolavirus , Hemorrhagic Fever, Ebola , Arthralgia/epidemiology , Asymptomatic Infections/epidemiology , Cohort Studies , Disease Progression , Fatigue/epidemiology , Hemorrhagic Fever, Ebola/complications , Hemorrhagic Fever, Ebola/epidemiology , Humans , Liberia/epidemiology , Longitudinal Studies , Memory Disorders/complications
13.
Viruses ; 14(8)2022 07 28.
Article in English | MEDLINE | ID: covidwho-1969499

ABSTRACT

In the COVID-19 epidemic the mildly symptomatic and asymptomatic infections generate a substantial portion of virus spread; these undetected individuals make it difficult to assess the effectiveness of preventive measures as most epidemic prevention strategies are based on the detected data. Effectively identifying the undetected infections in local transmission will be of great help in COVID-19 control. In this work, we propose an RNA virus transmission network representation model based on graph attention networks (RVTR); this model is constructed using the principle of natural language processing to learn the information of gene sequence and using a graph attention network to catch the topological character of COVID-19 transmission networks. Since SARS-CoV-2 will mutate when it spreads, our approach makes use of graph context loss function, which can reflect that the genetic sequence of infections with close spreading relation will be more similar than those with a long distance, to train our model. Our approach shows its ability to find asymptomatic spreaders both on simulated and real COVID-19 datasets and performs better when compared with other network representation and feature extraction methods.


Subject(s)
COVID-19 , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , Humans , SARS-CoV-2/genetics
14.
Math Biosci Eng ; 19(9): 9658-9696, 2022 07 04.
Article in English | MEDLINE | ID: covidwho-1954192

ABSTRACT

In this paper, we propose a new mathematical model to study the epidemic and economic consequences of COVID-19, with a focus on the interaction between the disease transmission, the pandemic management, and the economic growth. We consider both the symptomatic and asymptomatic infections and incorporate the effectiveness of disease control into the respective transmission rates. Meanwhile, the progression of the pandemic and the evolution of the susceptible, infectious and recovered population groups directly impact the mitigation and economic development levels. We fit this model to the reported COVID-19 cases and unemployment rates in the US state of Tennessee, as a demonstration of a real-world application of the modeling framework.


Subject(s)
COVID-19 , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , Humans , Models, Economic , Pandemics/prevention & control , SARS-CoV-2
15.
Epidemics ; 40: 100606, 2022 09.
Article in English | MEDLINE | ID: covidwho-1926431

ABSTRACT

BACKGROUND: The first wave of SARS-CoV-2 infection in Chile occurred during the cold season reaching a peak by the end of June 2020, with 80 % of the cases concentrated in its capital, Santiago. The main objective of this study was to estimate the attack rate during this first wave of SARS-CoV-2 in a large, densely populated city with more than seven million inhabitants. Since the number of confirmed cases provides biased information due to individuals' potential self-selection, mostly related to asymptomatic patients and testing access, we measured antibodies against SARS-CoV-2 to assess infection prevalence during the first wave in the city, as well as estimate asymptomatic cases, and infection fatality ratio. To our knowledge this is one of the few population-based cross-sectional serosurvey during the first wave in a highly affected emerging country. The challenges of pandemic response in urban settings in a capital city like Santiago, with heterogeneous subpopulations and high mobility through public transportation, highlight the necessity of more accurate information regarding the first waves of new emerging diseases. METHODS: From April 24 to June 21, 2020, 1326 individuals were sampled from a long-standing panel of household representatives of Santiago. Immunochromatographic assays were used to detect IgM and IgG antibody isotypes. RESULTS: Seroprevalence reached 6.79 % (95 %CI 5.58 %-8.26 %) in the first 107 days of the pandemic, without significant differences among sex and age groups; this figure indicates an attack rate 2.8 times higher than the one calculated with registered cases. It also changes the fatality rate estimates, from a 2.33 % case fatality rate reported by MOH to an estimated crude 1.00 % (CI95 % 0.97-1.03) infection fatality rate (adjusted for test performance 1.66 % [CI95 % 1.61-1.71]). Most seropositive were symptomatic (81,1 %). CONCLUSIONS: Despite the high number of cases registered, mortality rates, and the stress produced over the health system, the vast majority of the people remained susceptible to potential new epidemic waves. We contribute to the understanding of the initial spread of emerging epidemic threats. Consequently, our results provide better information to design early strategies that counterattack new health challenges in urban contexts.


Subject(s)
COVID-19 , SARS-CoV-2 , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , Chile/epidemiology , Cross-Sectional Studies , Humans , Immunoglobulin G , Immunoglobulin M , Seroepidemiologic Studies
16.
J Adv Res ; 39: 157-166, 2022 07.
Article in English | MEDLINE | ID: covidwho-1921030

ABSTRACT

INTRODUCTION: Different COVID-19 vaccine efficacies are reported, with remarkable effectiveness against severe disease. The so called sterilizing immunity, occurring when vaccinated individuals cannot transmit the virus, is still being evaluated. It is also unclear to what extent people with no symptoms or mild infection transmit the disease, and estimating their contribution to outbreaks is challenging. OBJECTIVE: With an uneven roll out of vaccination, the purpose of this study is to investigate the role of mild and asymptomatic infections on COVID-19 vaccine performance as vaccine efficacy and vaccine coverage vary. METHODS: We use an epidemiological SHAR (Susceptible-Hospitalized-Asymptomatic-Recovered) model framework to evaluate the effects of vaccination in different epidemiological scenarios of coverage and efficacy. Two vaccination models, the vaccine V1 protecting against severe disease, and the vaccine V2, protecting against infection as well as severe disease, are compared to evaluate the reduction of overall infections and hospitalizations. RESULTS: Vaccine performance is driven by the ability of asymptomatic or mild disease cases transmitting the virus. Vaccines protecting against severe disease but failing to block transmission might not be able to reduce significantly the severe disease burden during the initial stage of a vaccination roll out programme, with an eventual increase on the number of overall infections in a population. CONCLUSION: The different COVID-19 vaccines currently in use have features placing them closer to one or the other of these two extreme cases, V1 and V2, and insights on the importance of asymptomatic infection in a vaccinated population are of a major importance for the future planning of vaccination programmes. Our results give insights on how to best combine the use of the available COVID-19 vaccines, optimizing the reduction of hospitalizations.


Subject(s)
COVID-19 , Vaccines , Asymptomatic Infections/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines , Humans , Vaccination
17.
PLoS One ; 17(2): e0253638, 2022.
Article in English | MEDLINE | ID: covidwho-1910476

ABSTRACT

Population immunity (herd immunity) to SARS-CoV-2 derives from two sources: vaccinations or cases of infection with the virus. Infections can be diagnosed as COVID-19 and registered, or they can be asymptomatic, oligosymptomatic, or even full-blown but undiagnosed and unregistered when patients recovered at home. Estimation of population immunity to SARS-CoV-2 is difficult and remains a subject of speculations. Here we present a population screening for SARS-CoV-2 specific IgG and IgA antibodies in Polish citizens (N = 501) who had never been positively diagnosed with or vaccinated against SARS-CoV-2. Serum samples were collected in Wroclaw (Lower Silesia) on 15th and 22nd May 2021. Sera from hospitalized COVID-19 patients (N = 22) or from vaccinated citizens (N = 14) served as positive controls. Sera were tested with Microblot-Array COVID-19 IgG and IgA (quantitative) that contain specific SARS-CoV-2 antigens: NCP, RBD, Spike S2, E, ACE2, PLPro protein, and antigens for exclusion cross-reactivity with other coronaviruses: MERS-CoV, SARS-CoV, HCoV 229E Np, HCoV NL63 Np. Within the investigated population of healthy individuals who had never been positively diagnosed with or vaccinated against SARS-CoV-2, we found that 35.5% (178 out of 501) were positive for SARS-CoV-2-specific IgG and 52.3% (262 out of 501) were positive for SARS-CoV-2-specific IgA; 21.2% of the investigated population developed virus-specific IgG or IgA while being asymptomatic. Anti-RBD IgG, which represents virus-neutralizing potential, was found in 25.6% of individuals (128 out of 501). These patients, though positive for anti-SARS-CoV-2 antibodies, cannot be identified in the public health system as convalescents due to undiagnosed infections, and they are considered unaffected by SARS-CoV-2. Their contribution to population immunity against COVID-19 should however be considered in predictions and modeling of the COVID-19 pandemic. Of note, the majority of the investigated population still lacked anti-RBD IgG protection (74.4%); thus vaccination against COVID-19 is still of the most importance for controlling the pandemic.


Subject(s)
Asymptomatic Infections/epidemiology , COVID-19 Vaccines/therapeutic use , COVID-19/epidemiology , COVID-19/immunology , Immunity, Herd , Pandemics/prevention & control , SARS-CoV-2/immunology , Vaccination/methods , Adolescent , Adult , Aged , Antibodies, Viral/blood , Antibodies, Viral/immunology , Antigens, Viral/immunology , COVID-19/blood , COVID-19/prevention & control , Cross Reactions , Female , Humans , Immunoglobulin A/blood , Immunoglobulin A/immunology , Immunoglobulin G/blood , Immunoglobulin G/immunology , Male , Middle Aged , Poland/epidemiology , Treatment Outcome , Young Adult
18.
Zhonghua Wei Zhong Bing Ji Jiu Yi Xue ; 34(5): 449-453, 2022 May.
Article in Chinese | MEDLINE | ID: covidwho-1903530

ABSTRACT

OBJECTIVE: To analyze the clinical characteristics and prognosis of patients infected with novel coronavirus Omicron variant in Shanghai, as to provide a reference for epidemic prevention, clinical diagnosis, and treatment. METHODS: Altogether 4 264 novel coronavirus Omicron variant-infected patients with positive results of nucleic acid admitted to Shanghai New International Expo Center N3 Mobile Cabin Hospital from April 2 to May 7, 2022, were included. The demographic and baseline clinical characteristics, treatment strategy, prognosis, and different factors affecting the length of hospital stay were analyzed. RESULTS: A total of 4 264 novel coronavirus variant Omicron-infected cases were collected, including 3 111 cases (73.0%) asymptomatic infections and 1 153 cases (27.0%) mild infections. The overall median age was 45 (33, 55) years old with a range from 2 years old to 81 years old. The male to female ratio was 1.37:1. Altogether 3 305 cases (77.5%) had been vaccinated, of which 3 166 cases completed more than 2 doses. The upper respiratory tract symptoms such as cough and expectoration were the most common clinical manifestations of these infected patients. During the course of the disease, patients with asymptomatic infection were mainly treated with traditional Chinese medicine (TCM, 55.1%) and clinical observation (36.8%), and those with mild infection were mainly treated with TCM (42.2%) or integrated Chinese and Western medicine (30.4%). All patients were cured and discharged. The overall median length of hospital stay and the negative conversion time of nucleic acid were 9 (6, 10) days and 8 (5, 9) days, respectively. Compared with the asymptomatic infected patients, the hospitalization duration and the nucleic acid negative conversion time of the mildly infected patients were slightly longer [days: 10 (8, 11) vs. 9 (5, 10); 8 (6, 10) vs. 7 (4, 9), both P < 0.001]. Multiple linear regression analysis showed that the increasing age and mild infection were associated with longer hospitalization duration, and the treatment of TCM or integrated Chinese and Western medicine was associated with shortened length of hospital stay (all P < 0.05). CONCLUSIONS: The current novel coronavirus Omicron variant epidemic in Shanghai mainly caused asymptomatic and mild infections. The young and middle-aged population had a relatively high infection rate. The upper respiratory tract symptoms such as cough and expectoration were the most common clinical symptoms. Elderly and confirmed patients had prolonged hospitalization duration, while for patients receiving TCM treatment, the hospitalization duration was shortened.


Subject(s)
COVID-19 , Adolescent , Adult , Aged , Aged, 80 and over , Asymptomatic Infections/epidemiology , COVID-19/diagnosis , COVID-19/drug therapy , COVID-19/epidemiology , Child , Child, Preschool , China/epidemiology , Cough , Female , Hospitalization , Humans , Length of Stay , Male , Medicine, Chinese Traditional , Middle Aged , Prognosis , Retrospective Studies , SARS-CoV-2 , Young Adult
19.
Immun Inflamm Dis ; 10(7): e670, 2022 07.
Article in English | MEDLINE | ID: covidwho-1894599

ABSTRACT

BACKGROUND: Asymptomatic infections may play an important role in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) Delta variant transmissions. However, the immunologic features of asymptomatic postvaccination infections with the Delta variant of SARS-CoV-2 in adults remain to be defined. METHODS: A retrospective study involving 36 vaccinated adults infected with the SARS-CoV-2 Delta variant was performed. Their demographic and laboratory data were collected and analyzed in The First People's Hospital of Jingmen from August 4 to 20, 2021. RESULTS: Of the 36 adults, 6 persons had an asymptomatic infection. The severity of the SARS-CoV-2 infections was highly correlated with the doses of vaccinations (p = 0.019). The symptomatic and asymptomatic infected SARS-CoV-2 adults showed normal levels of leukocytes and lymphocytes. The C-reactive protein (CRP) and interleukin-6 (IL-6) levels were elevated in the symptomatic groups. The period between the last vaccination to the time of infection in the asymptomatic group was longer than that in the mild and moderate groups (73 vs. 61 vs. 50 days; p = 0.047). The percentage of suppressor T-cells in the asymptomatic group was the highest (32.2 ± 4.0% vs. 22.0 ± 7.2% vs. 29.3 ± 8.0%; p = 0.004). The signal-to-cutoff ratio value of total antibody against SARS-CoV-2 in the asymptomatic group was lower than that in the other two groups (383 vs. 703 vs. 1792; p < 0.001) and much lower than that in the moderate group. The multivariate ordinal logistic analysis after adjusting for gender, vaccination date, and vaccination dose indicated that CRP at Days 4-7 and 8-14, IL-6 on Days 4-7, and total antibody were risk factors for coronavirus disease 2019 severity. CONCLUSIONS: Asymptomatic postvaccination infections with the Delta variant of SARS-CoV-2 in adults tend to infect persons vaccinated twice. The immunophenotype profile for asymptomatic postvaccination infections is less inflammatory and accompanied by relatively lower antibody titers.


Subject(s)
COVID-19 , SARS-CoV-2 , Adult , Asymptomatic Infections/epidemiology , COVID-19/epidemiology , COVID-19/prevention & control , Humans , Interleukin-6 , Retrospective Studies
20.
J Infect Dev Ctries ; 16(5): 768-777, 2022 05 30.
Article in English | MEDLINE | ID: covidwho-1879508

ABSTRACT

Despite efforts to contain and manage the SARS-CoV-2 outbreak which was declared a public health emergency of international concern in January 2020 by the World Health Organization (WHO), the COVID-19 pandemic still remains a major global challenge. Patients who display the classical symptoms of the infection are easily identified, tested, isolated and monitored. However, many cases of infected asymptomatic patients have been documented. These patients are not easily identified even though many evidences suggest that they can spread the virus to others. How and why these COVID-19 asymptomatic presentations occur remain unclear. The many theories and views are conjectural, and supporting evidences are still needed. In this review, we described the trend in SARS-CoV-2 viral shedding and susceptibility, providing perspectives on gender differences and asymptomatic patients. We further discussed how genetics, gender, viral inoculum, and pre-existing immunity may influence asymptomatic presentations in COVID-19 infections. We hope that this article improves our understanding of asymptomatic SAR-CoV-2 infection and it sheds light on some salient areas that should be considered as the search for a potent vaccine continues.


Subject(s)
COVID-19 , SARS-CoV-2 , Asymptomatic Infections/epidemiology , Humans , Pandemics , Virus Shedding
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