• COVID-19
• Coronavirus
• Dry eye
• OSDI
• SARS-CoV-2

• European Commission

• COVID-19
• Cairo University hospital
• Healthcare workers
• anxiety
• depression
• post-traumatic stress disorder.
• psychological symptoms
• stigma perception

• COVID-19
• SARS
• health planning
• risk communication
• risk management

• Humans
• COVID-19
• SARS-CoV-2
• Emergencies
• Communication
• Risk Management

Some asymptomatic individuals carrying SARS-CoV-2 can transmit the virus and contribute to outbreaks of COVID-19. Here, we use detailed surveillance data gathered during COVID-19 resurgences in six cities of China at the beginning of 2021 to investigate the relationship between asymptomatic proportion and age. Epidemiological data obtained before mass vaccination provide valuable insights into the nature of pathogenicity of SARS-CoV-2. The data were collected by multiple rounds of city-wide PCR testing with contact tracing, where each patient was monitored for symptoms through the whole course of infection. The clinical endpoint (asymptomatic or symptomatic) for each patient was recorded (the pre-symptomatic patients were classified as symptomatic). We find that the proportion of infections that are asymptomatic declines with age (coefficient = −0.006, 95% CI: −0.008 to −0.003, p < 0.01), falling from 42% (95% CI: 6–78%) in age group 0–9 years to 11% (95% CI: 0–25%) in age group greater than 60 years. Using an age-stratified compartment model, we show that this age-dependent asymptomatic pattern, together with the distribution of cases by age, can explain most of the reported variation in asymptomatic proportions among cities. Our analysis suggests that SARS-CoV-2 surveillance strategies should take account of the variation in asymptomatic proportion with age.

• sars-cov-2
• asymptomatic infection
• age-stratified compartment model

• Immune responses
• Immunoglobulin
• Infection
• SARS coronavirus
• Virus classification

The comprehensive understanding of the characteristics of asymptomatic cases are helpful for the identification and management of patients with asymptomatic COVID-19 infection. Four electronic databases were searched from December 1, 2019 to February 8, 2022 for relevant articles. Data synthesis, subgroup analysis, and sensitivity analysis were performed on the included studies. I² and Q tests were applied to evaluate heterogeneity across studies. The risk of publication bias was assessed and visualized using a funnel plot. A total of 45 studies consisting of 2,655 patients with no symptoms at the screening point were included. Pooled results showed that in China, 65% of initial no-symptoms COVID-19 patients did not present any COVID-19-related symptom during follow-up or by end of disease course (asymptomatic infections). High proportions of initial no-symptoms COVID-19 patients (76%) and patients with asymptomatic infection (55%) had abnormal CT features at the screening point. High proportion of patients with asymptomatic infection had been detected Ig G⁺ (72%) and/or Ig M⁺ (57%) at the screening point. The chest CT scan and SARS-CoV-2-specific antibody testing could serve as effective supplementary methods to identify asymptomatic cases in the early stage of SARS-CoV-2 infection. However, the chest CT scan and the SARS-CoV-2-specific IgM and IgG testing should not replace reverse transcription–polymerase chain reaction (RT-PCR) for screening in asymptomatic patients. The combination of repeated RT-PCR, chest CT scans, and the SARS-CoV-2-specific IgM and IgG testing should be performed for those highly suspected SARS-CoV-2 infections.

• COVID-19
• CT
• SARS-CoV-2
• asymptomatic infection
• presymptomatic infection

The COVID-19 pandemic has disrupted people's normal life as a result of strict policies applied to slow down the pandemic. To find out how extensive the virus spread is, most countries increase their daily testing rates.

This simple modelling work uses stringency index and daily testing (including the lagged version up to the previous 14 days) to predict daily COVID-19 cases in India and Indonesia. A Stepwise Multiple Regression (SWMR) subroutine is used in this modelling to select factors based on a 0.01 significant level affecting daily COVID-19 cases before the epidemic peaks.

The models have high predictability close to 94% (Indonesia) and 99% (India). Increasing number of daily COVID-19 cases in Indonesia is associated with the country's increased testing capacity. On the other hand, stringency indices play more important role in determining India's daily COVID-19 cases.

Our finding shows that one question remains to be answered as to why testing and strict policy differ in determining daily cases in both Asian countries.

• COVID-19
• Pandemic

• respiratory tract microbiota
• defensins and lactoferrin
• surfactant proteins
• epithelial cell interferons
• innate immunity

• Antibodies, Viral/immunology
• Antimicrobial Peptides/immunology
• COVID-19/immunology
• Humans
• Immunity, Innate
• Immunoglobulin A/immunology
• Interferons/immunology
• Lung/immunology
• Lung/virology
• SARS-CoV-2

• COVID-19
• SARS-CoV-2
• dental practice
• infection
• procedure

• COVID-19
• COVID-19 post-intensive care syndrome
• homoeopathy
• post-acute COVID-19 syndrome
• post-acute sequelae of SARS-CoV-2 infection

• asymptomatic fraction
• comorbidity
• novel coronavirus
• presymptomatic
• silent transmission

• Asymptomatic Infections/epidemiology
• COVID-19/diagnosis
• COVID-19/epidemiology
• COVID-19/virology
• Humans
• SARS-CoV-2/isolation & purification

• R01 AI151176 NIAID NIH HHS
• 1R01 AI151176-01 NIH HHS

Universal testing for COVID-19 on admission to the labor and delivery unit identifies asymptomatic patients. Whether or not these patients are at increased risk for adverse outcomes and go on to develop clinically significant disease is uncertain.

This study aimed to assess the prevalence of asymptomatic COVID-19 presentation among pregnant patients admitted for delivery and to determine whether these patients become symptomatic or require hospital readmission after discharge.

We performed a multicenter, prospective cohort study of pregnant patients who delivered between 20^0/7 and 41^6/7 weeks’ gestation and who were found to have COVID-19 based on universal screening on admission for delivery at 1 of 4 medical centers in New Jersey (exposed group). The unexposed group, comprising patients who tested negative for COVID-19, were identified at the primary study site. The primary outcomes were the rates of asymptomatic COVID-19 presentation, the development of symptoms among the asymptomatic positive patients, and hospital readmission rates in the 2 weeks following discharge. We compared the frequency of the distribution of risk factors and outcomes in relation to the COVID-19 status among patients with COVID-19 across all centers and among those without COVID-19 at the primary site. Associations between categorical risk factors and COVID-19 status were expressed as relative risks with 95% confidence intervals.

Between April 10, 2020, and June 15, 2020, there were 218 patients with COVID-19 at the 4 sites and 413 patients without COVID-19 at the primary site. The majority (188 [83.2%]) of patients with COVID-19 were asymptomatic. Compared with the negative controls, these asymptomatic patients were not at increased risk for obstetrical complications that may increase the risk associated with COVID-19, including gestational diabetes (8.2% vs 11.4%; risk ratio, 0.72; 95% confidence interval, 0.24–2.01) and gestational hypertension (6.1% vs 7.0%; risk ratio, 0.88; 95% confidence interval, 0.29–2.67). Postpartum follow-ups via telephone surveys revealed that these patients remained asymptomatic and had low rates of family contacts acquiring the disease, but their adherence to social distancing guidelines waned during the 2-week postpartum period. Review of inpatient and emergency department records revealed low rates of hospital readmission.

Most of the pregnant patients who screened positive for COVID-19 are asymptomatic and do not go on to develop clinically significant infection after delivery. Routine surveillance of these patients after hospital discharge appears to be sufficient.

• COVID-19
• SARS-CoV-2
• asymptomatic disease
• multicenter prospective cohort study
• pregnancy

• Diagnostics
• case definition
• consensus
• golden standard
• metagenomics

• viral infection
• fatigue
• fever
• respiratory signs and symptoms

• Adolescent
• Adult
• Aged
• Antibodies, Viral/blood
• Brazil/epidemiology
• COVID-19/epidemiology
• COVID-19/immunology
• Carrier State/immunology
• Child
• Child, Preschool
• Female
• Humans
• Immunoglobulin G/blood
• Immunoglobulin M/blood
• Infant
• Infant, Newborn
• Male
• Middle Aged
• Prevalence
• Seroepidemiologic Studies
• Young Adult

• Ministério da Saúde
• Instituto Serrapilheira
• JBS S.A. initiative Fazer o Bem Faz Bem
• Brazilian Collective Health Association (ABRASCO)

Notifications of novel coronavirus infections increased in early 2020 in Japan. We described characteristics of novel coronavirus infection cases and analyzed risk factors for severe outcomes.

Cases were persons with laboratory-confirmed novel coronavirus infection reported under national surveillance between January and March 2020. Clinical characteristics were described, and risk factors of (1) intensive care unit [ICU] admission and (2) invasive ventilation/death were analyzed using Poisson regression.

Among the 516 cases analyzed, median age was 60 years (range: 1–97 years) and 285 (55%) were male. Common symptoms/signs were fever (375/475, 79%), cough (353/465, 76%), and pneumonia (245/387, 63%). Ten (2%) cases died. Of the 348 cases with data, 50 (14%) required invasive ventilation. Adjusted for each other, male gender and 1-year increase in age were associated with ICU admission (risk ratio [RR] 4.18; 95% confidence interval [CI], 1.69–10.32 and RR 1.05; 95% CI, 1.03–1.08, respectively) and invasive ventilation/death (RR 2.79; 95% CI, 1.49–5.21 and RR 1.06; 95% CI, 1.04–1.08, respectively). Diabetes, dyslipidemia, hyperuricemia, and lung diseases were also associated with severe outcomes. Of the 80 cases asymptomatic at hospitalization, 40 developed symptoms and five of them >70 years of age required invasive ventilation.

The early stage of the novel coronavirus epidemic in Japan disproportionately affected the elderly. Older age, male gender, and underlying conditions were associated with severe outcomes. Notably, some elderly case-patients who were asymptomatic at diagnosis and promptly hospitalized still went on to develop severe disease, indicating the importance of careful monitoring of certain populations.

• SARS-CoV-2
• clinical characteristic
• epidemiology
• risk factor
• surveillance

The ongoing SARS-CoV-2 pandemic has spread rapidly worldwide and disease prevention is more important than ever. In the absence of a vaccine, knowledge of the transmission routes and risk areas of infection remain the most important existing tools to prevent further spread.

Here we investigated the presence of the SARS-CoV-2 virus in the hospital environment at the Uppsala University Hospital Infectious Disease ward by RT-qPCR and determined the infectivity of the detected virus in vitro on Vero E6 cells.

SARS-CoV-2 RNA was detected in several areas, although attempts to infect Vero E6 cells with positive samples were unsuccessful. However, RNase A treatment of positive samples prior to RNA extraction did not degrade viral RNA, indicating the presence of SARS-CoV-2 nucleocapsids or complete virus particles protecting the RNA as opposed to free viral RNA.

Our results show that even in places where a moderate concentration (Ct values between 30 and 38) of SARS-CoV-2 RNA was found; no infectious virus could be detected. This suggests that the SARS-CoV-2 virus in the hospital environment subsides in two states; as infectious and as non-infectious. Future work should investigate the reasons for the non-infectivity of SARS-CoV-2 virions.

The online version contains supplementary material available at 10.1186/s12985-021-01556-6.

• COVID-19
• Environmental sampling
• In vitro infection
• RNase A
• SARS-CoV-2
• Viral infectivity

• COVID-19
• Cohort study
• Consecutive
• Early
• PR-PCR tests

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• COVID-19/diagnosis
• COVID-19 Nucleic Acid Testing/methods
• Cohort Studies
• Female
• Humans
• Male
• Middle Aged
• Oropharynx/virology
• SARS-CoV-2/isolation & purification
• Sputum/virology
• Young Adult

• COVID-19
• England
• SARS-CoV-2
• antibodies
• immunity
• seroepidemiology

• COVID-19
• SARS
• SARS-CoV-2
• cross-reactivity
• seroprevalence

• Adult
• Antibodies, Viral/blood
• Antibodies, Viral/immunology
• COVID-19/epidemiology
• COVID-19/immunology
• Cross Reactions
• Cross-Sectional Studies
• Disease Outbreaks
• Female
• Humans
• Immunoglobulin G/blood
• Immunoglobulin G/immunology
• Incidence
• Male
• Middle Aged
• SARS-CoV-2/immunology
• Seroepidemiologic Studies
• Severe Acute Respiratory Syndrome/epidemiology
• Severe Acute Respiratory Syndrome/immunology
• Taiwan/epidemiology

Moderate cases account for the majority in hospitalized patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and can also progress to severe/critical condition. Here, we investigated the clinical course and management of hospitalized moderate SARS-CoV-2 patients. The medical records and follow-up data were analyzed from the SARS-CoV-2 patients outside Wuhan. A total of 73 moderate patients (38 men, 35 women) were included, with median age of 47.0 (38.5–57.5) years. Among them, only one patient (1.4%) died using active treatment to improve symptoms. The median duration of the four main symptoms cough, fever, chest tightness, and fatigue were 11.0, 8.0, 11.0, and 7.0 days, respectively; the median duration of the positive nucleic acid test (NAT) results for SARS-CoV-2 was 16.5 days; the median hospitalization time was 25.0 days in 72 moderate survivors. The duration of cough and fever was positively correlated with the duration of the positive NAT results. On admission, 50% had lymphopenia; less than 30% had abnormal blood biochemistry findings involving hyperglycemia, liver function and myocardial enzymes. At discharge, the laboratory indexes were substantially improved. Two weeks after discharge, 5.6% survivors experienced a recurrence of the positive NAT results. Moderate SARS-CoV-2 patients have a good prognosis by the active treatment. A small proportion of the recovered moderate patients still may be virus carriers and require an additional round of viral detection.

• Adult
• Antiviral Agents/therapeutic use
• COVID-19/blood
• COVID-19/diagnosis
• COVID-19/epidemiology
• COVID-19/therapy
• China/epidemiology
• Disease Management
• Female
• Follow-Up Studies
• Hospitalization
• Humans
• Male
• Middle Aged
• Retrospective Studies
• SARS-CoV-2/isolation & purification

• Key Laboratory of Tumor Precision Medicine, Hunan colleges and Universities Project
• Science and Technology Funding Project of Chenzhou, Hunan province, China
• Health Commission Funding Project of Hunan province, China

• COVID-19
• Hong Kong
• epidemic
• instantaneous asymptomatic proportion
• likelihood-based framework

The current gold standard for the diagnosis of coronavirus disease-19 (COVID-19) is a positive reverse transcriptase polymerase chain reaction (RT-PCR) test, on the background of clinical suspicion. However, RT-PCR has its limitations; this includes issues of low sensitivity, sampling errors and appropriate timing of specimen collection. As pulmonary involvement is the most common manifestation of severe COVID-19, early and appropriate lung imaging is important to aid diagnosis. However, gross discrepancies can occur between the clinical and imaging findings in patients with COVID-19, which can mislead clinicians in their decision making. Although chest X-ray (CXR) has a low sensitivity for the diagnosis of COVID-19 associated lung disease, especially in the earlier stages, a positive CXR increases the pre-test probability of COVID-19. CXR scoring systems have shown to be useful, such as the COVID-19 opacification rating score which helps to predict the need of tracheal intubation. Furthermore, artificial intelligence-based algorithms have also shown promise in differentiating COVID-19 pneumonia on CXR from other lung diseases. Although costlier than CXR, unenhanced computed tomographic (CT) chest scans have a higher sensitivity, but lesser specificity compared to RT-PCR for the diagnosis of COVID-19 pneumonia. A semi-quantitative CT scoring system has been shown to predict short-term mortality. The routine use of CT pulmonary angiography as a first-line imaging modality in patients with suspected COVID-19 is not justifiable due to the risk of contrast nephropathy. Scoring systems similar to those pioneered in CXR and CT can be used to effectively plan and manage hospital resources such as ventilators. Lung ultrasound is useful in the assessment of critically ill COVID-19 patients in the hands of an experienced operator. Moreover, it is a convenient tool to monitor disease progression, as it is cheap, non-invasive, easily accessible and easy to sterilise. Newer lung imaging modalities such as magnetic resonance imaging (MRI) for safe imaging among children, adolescents and pregnant women are rapidly evolving. Imaging modalities are also essential for evaluating the extra-pulmonary manifestations of COVID-19: these include cranial imaging with CT or MRI; cardiac imaging with ultrasonography (US), CT and MRI; and abdominal imaging with US or CT. This review critically analyses the utility of each imaging modality to empower clinicians to use them appropriately in the management of patients with COVID-19 infection.

• COVID-19
• Pneumonia
• Lung imaging
• Chest X-ray
• Computed tomography
• Lung ultrasound

The proportion of UK oncology healthcare professionals (HCPs) infected with SARS-CoV-2 during the COVID-19 pandemic's first wave is unknown. The primary aim of this study was to determine the SARS-CoV-2 infection and seroprevalence rates among HCPs.

Patient-facing oncology HCPs working at three large UK hospitals during the COVID-19 pandemic's first wave underwent polymerase chain reaction (PCR) and antibody testing [Luminex and point-of-care (POC) tests] on two occasions 28 days apart (June–July 2020).

In total, 434 HCPs were recruited: nurses (58.3%), doctors (21.2%), radiographers (10.4%), administrators (10.1%); 26.3% reported prior symptoms suggestive of SARS-CoV-2. All participants were PCR negative during the study, but 18.4% were Luminex seropositive on day 1, of whom 42.5% were POC seropositive. Nurses had the highest seropositive prevalence trend (21.3%, P = 0.2). Thirty-eight per cent of seropositive HCPs reported previous SARS-CoV-2 symptoms: 1.9 times higher odds than seronegative HCPs (P = 0.01). Of 400 participants retested on day 28, 13.3% were Luminex seropositive (92.5% previously, 7.5% newly). Thirty-two per cent of initially seropositive HCPs were seronegative on day 28.

In this large cohort of PCR-negative patient-facing oncology HCPs, almost one in five were SARS-CoV-2 antibody positive at the start of the pandemic's first wave. Our findings that one in three seropositive HCPs retested 28 days later became seronegative support regular SARS-CoV-2 PCR and antibody testing until widespread immunity is achieved by effective vaccination.

• Antibody
• COVID-19
• PCR
• SARS-CoV-2
• healthcare professionals
• serology

While the role of contact tracing in the containment of the COVID-19 epidemic remains important until vaccines are widely available, literature on objectively measurable indicators for the effectiveness of contact tracing is scarce. We suggest the diagnostic serial interval, the time between the diagnosis of the infector and infectee, as a new indicator for the effectiveness of contact tracing.

Using an agent-based simulation model, we demonstrate how the diagnostic serial interval correlates with the course of the epidemic. We consider four scenarios of how diagnosis and subsequent isolation are triggered: 1. never, 2. by symptoms, 3. by symptoms and loose contact tracing, 4. by symptoms and tight contact tracing. We further refine scenarios 3 and 4 with different lengths of target diagnostic serial intervals.

Scenarios 1 and 2 did not yield a notable difference. In scenarios 3 and 4, however, contact tracing led to a decrease of the height of the epidemic as well as the cumulative proportion of infected agents. Generally, the shorter the diagnostic serial interval was, the smaller the peak of the epidemic became, and the more proportion of the population remained susceptible at the end of the epidemic.

A short target diagnosis interval is critical for contact tracing to be effective in the epidemic control. The diagnosis interval can be used to assess and guide the contact tracing strategy.

• Agent based model
• COVID-19
• Contact tracing
• Diagnostic serial interval
• Epidemic control
• SARS-CoV-2
• Serial interval

COVID-19 can be asymptomatic in a substantial proportion of patients. The assessment and management of these patients constitute a key element to stop dissemination.

To describe the assessment and treatment of asymptomatic infection in patients with a confirmed diagnosis of COVID-19.

We searched five databases and search engines for preprints/preproofs, up to August 22, 2020. We included cohort, cross-sectional, and case series studies, reporting the assessment and management of asymptomatic individuals. We extracted data on total discharges with negative PCR, length of hospitalization, treatment, and number of patients who remained asymptomatic. A random-effects model with inverse variance method was used to calculate the pooled prevalence.

41 studies (nine cross-sectional studies, five retrospective studies and 27 reports/case series; 647 asymptomatic individuals), were included, of which 47% were male (233/501). The age of patients was between 1month and 73 years. In patients who became symptomatic, length of hospitalization mean was 13.6 days (SD 6.4). Studies used lopinavir/ritonavir, hydroxychloroquine plus ritonavir/lopinavir, hydroxychloroquine with and without azithromycin, ribavirin plus interferon and interferon alfa. The proportion of individuals who remained asymptomatic was 91% (463/588 patients; 95%CI: 78.3%–98.7%); and asymptomatic individuals discharged with negative PCR was 86% (102/124 individuals; 95%CI: 58.4%–100%).

There is no standard treatment for asymptomatic COVID-19 individuals. There are no studies of adequate design to make this decision. It has been shown that most asymptomatic individuals who were followed have recovered, but this cannot be attributed to standard treatment.

• Asymptomatic
• COVID-19
• SARS-CoV-2
• Systematic review

• asymptomatic COVID-19
• characteristics
• pneumonia
• spectrum
• symptomatic

• COVID-19 vaccine
• Nanovaccine
• SARS-CoV-2
• mRNA vaccine

• Animals
• COVID-19/immunology
• COVID-19/prevention & control
• COVID-19 Vaccines/administration & dosage
• COVID-19 Vaccines/immunology
• Drug Carriers/administration & dosage
• Drug Delivery Systems/methods
• Drug Delivery Systems/trends
• Humans
• Nanocapsules/administration & dosage
• SARS-CoV-2/drug effects
• SARS-CoV-2/immunology
• Viral Vaccines/administration & dosage
• Viral Vaccines/immunology

• R01 NS036126 NINDS NIH HHS
• R01 MH115860 NIMH NIH HHS
• P01 DA028555 NIDA NIH HHS
• P30 MH062261 NIMH NIH HHS
• F31 NS042419 NINDS NIH HHS
• T32 NS105594 NINDS NIH HHS
• R01 MH121402 NIMH NIH HHS
• R01 AG043530 NIA NIH HHS
• R01 AG043540 NIA NIH HHS
• R01 NS034239 NINDS NIH HHS

• Asymptomatic Infections/epidemiology
• COVID-19/epidemiology
• COVID-19/pathology
• COVID-19/virology
• Databases, Factual
• Humans
• SARS-CoV-2/isolation & purification

• COVID-19
• Laboratory Diagnosis
• Polymerase Chain Reaction
• SARS-CoV-2

• COVID-19/diagnosis
• COVID-19 Testing
• Humans
• Molecular Diagnostic Techniques
• Sensitivity and Specificity

• Adolescent
• Adult
• Aged
• Asymptomatic Diseases/epidemiology
• COVID-19/diagnosis
• COVID-19/epidemiology
• COVID-19/virology
• Child
• China/epidemiology
• Cough/diagnosis
• Cough/epidemiology
• Cough/virology
• Female
• Fever/diagnosis
• Fever/epidemiology
• Fever/virology
• Humans
• Male
• Middle Aged
• Retrospective Studies
• SARS-CoV-2/genetics
• SARS-CoV-2/isolation & purification
• SARS-CoV-2/physiology
• Young Adult

• COVID-19
• Pregnancy
• Presymptomatic
• SARS-CoV-2
• asymptomatic
• household contact
• transmission

• COVID-19
• asymptomatic
• pregnancy
• thromboembolism risk
• vertical transmission

• Drugs
• High-Performance Computing in Bioinformatics
• Structural Biology
• Virology

• R01 GM136859 NIGMS NIH HHS
• R01 AI037581 NIAID NIH HHS
• R01 AI128364 NIAID NIH HHS
• P01 AI120943 NIAID NIH HHS
• R01 CA200913 NCI NIH HHS

• COVID-19
• SARS-CoV-2
• cohort study
• social distancing
• viral inoculum

• Adult
• COVID-19
• Cohort Studies
• Humans
• Male
• Physical Distancing
• SARS-CoV-2
• Switzerland/epidemiology
• Young Adult

• MC_PC_12009 Medical Research Council
• MC_PC_17230 Medical Research Council

• COVID-19
• Epidemic modeling
• Social distancing

• Asymptomatic Infections/epidemiology
• Basic Reproduction Number/statistics & numerical data
• COVID-19/epidemiology
• COVID-19/prevention & control
• COVID-19/transmission
• Disease Susceptibility/epidemiology
• Humans
• Mathematical Concepts
• Models, Biological
• Pandemics/prevention & control
• Pandemics/statistics & numerical data
• Physical Distancing
• SARS-CoV-2
• Systems Biology
• Time Factors

• COVID-19
• Epidemic modeling
• Social distancing

• Asymptomatic Infections/epidemiology
• Basic Reproduction Number/statistics & numerical data
• COVID-19/epidemiology
• COVID-19/prevention & control
• COVID-19/transmission
• Disease Susceptibility/epidemiology
• Humans
• Mathematical Concepts
• Models, Biological
• Pandemics/prevention & control
• Pandemics/statistics & numerical data
• Physical Distancing
• SARS-CoV-2
• Systems Biology
• Time Factors

• asymptomatic carriers
• clinical characteristics
• coronavirus disease 2019
• infectivity