Asymptomatic versus symptomatic SARS-CoV-2 infection: a cross-sectional seroprevalence study.

BACKGROUND: Although symptomatic SARS-CoV-2 infection predisposes patients to develop complications, the asymptomatic SARS-CoV-2 infection state is of public health importance being a hidden source of infection. Moreover, the asymptomatic state may camouflage the actual burden of the disease. METHODS: Data of 1434 seropositive participants for SARS-CoV-2 spike (anti-S) and/or nucleocapsid antibodies (anti-N) were retrieved from a larger cross-sectional survey on COVID-19. Relevant data were retrieved from records including socio-demographic, medical, and behavioral characteristics of seropositive participants as well as history of COVID-19 symptoms during the last 6 months. Symptomatic/asymptomatic SARS-CoV-2 infection was categorized based on the history of the presence or absence of COVID-19 symptoms. RESULTS: The rate of asymptomatic SARS-CoV-2 infection was 34.9%. There was a statistically significant difference between symptomatic and asymptomatic participants regarding age, residence, medical conditions, habits, and infection control measures. The number of symptoms was positively correlated with anti-S titer and both were positively correlated with adult body mass index. Slum areas residence, client-facing occupation or being a healthcare worker, having lung disease, having blood group type A, never practicing exercise or social distancing, never using soap for hand washing, and minimal engagement in online working/studying were independent factors associated with the symptomatic state. Patients having less than three symptoms were less likely to be diagnosed by any means. CONCLUSIONS: One-third of SARS-CoV-2 infections in our study were asymptomatic. This mandates applying proper measures to prevent transmission even from apparently healthy individuals. Modifiable factors associated with symptomatic infection should be controlled to reduce the risk of COVID-19 complications.

Cross-sectional analysis of students and school workers reveals a high number of asymptomatic SARS-CoV-2 infections during school reopening in Brazilian cities.

Brazil experienced one of the most prolonged periods of school closures, and reopening could have exposed students to high rates of SARS-CoV-2 infection. However, the infection status of students and school workers at the time of the reopening of schools located in Brazilian cities is unknown. Here we evaluated viral carriage by RT-PCR and seroprevalence of anti-SARS-CoV-2 antibodies (IgM and IgG) by immunochromatography in 2259 individuals (1139 students and 1120 school workers) from 28 schools in 28 Brazilian cities. We collected the samples within 30 days after public schools reopened and before the start of vaccination campaigns. Most students (n = 421) and school workers (n = 446) had active (qRT-PCR + IgM- IgG- or qRT-PCR + IgM + IgG-/+) SARS-CoV-2 infection. Regression analysis indicated a strong association between the infection status of students and school workers. Furthermore, while 45% (n = 515) of the students and 37% (n = 415) of the school workers were neither antigen nor antibody positive in laboratory tests, 16% of the participants (169 students and 193 school workers) were oligosymptomatic, including those reinfected. These individuals presented mild symptoms such as headache, sore throat, and cough. Notably, most of the individuals were asymptomatic (83.9%). These results indicate that many SARS-CoV-2 infections in Brazilian cities during school reopening were asymptomatic. Thus, our study highlights the need to promote a coordinated public health effort to guarantee a safe educational environment while avoiding exacerbating pre-existent social inequalities in Brazil, reducing social, mental, and economic losses for students, school workers, and their families.

Long-Term Longitudinal Analysis of Neutralizing Antibody Response to Three Vaccine Doses in a Real-Life Setting of Previously SARS-CoV-2 Infected Healthcare Workers: A Model for Predicting Response to Further Vaccine Doses.

We report the time course of neutralizing antibody (NtAb) response, as measured by authentic virus neutralization, in healthcare workers (HCWs) with a mild or asymptomatic SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection diagnosed at the onset of the pandemic, with no reinfection throughout and after a three-dose schedule of the BNT162b2 mRNA vaccine with an overall follow-up of almost two years since infection. Forty-eight HCWs (median age 47 years, all immunocompetent) were evaluated: 29 (60.4%) were asymptomatic. NtAb serum was titrated at eight subsequent time points: T1 and T2 were after natural infection, T3 on the day of the first vaccine dose, T4 on the day of the second dose, T5, T6, and T7 were between the second and third dose, and T8 followed the third dose by a median of 34 days. NtAb titers at all postvaccination time points (T4 to T8) were significantly higher than all those at prevaccination time points (T1 to T3). The highest NtAb increase was following the first vaccine dose while subsequent doses did not further boost NtAb titers. However, the third vaccine dose appeared to revive waning immunity. NtAb levels were positively correlated at most time points suggesting an important role for immunogenetics.

Field Performance and Public Health Response Using the BinaxNOWTM Rapid Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antigen Detection Assay During Community-Based Testing.

Among 3302 persons tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by BinaxNOWTM and reverse transcription polymerase chain reaction (RT-PCR) in a community setting, rapid assay sensitivity was 100%/98.5%/89% using RT-PCR cycle thresholds of 30, 35, and no threshold. The specificity was 99.9%. Performance was high across ages and those with and without symptoms. Rapid resulting permitted immediate public health action.

Community Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Disproportionately Affects the Latinx Population During Shelter-in-Place in San Francisco.

BACKGROUND: There is an urgent need to understand the dynamics and risk factors driving ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during shelter-in-place mandates. METHODS: We offered SARS-CoV-2 reverse-transcription polymerase chain reaction (PCR) and antibody (Abbott ARCHITECT IgG) testing, regardless of symptoms, to all residents (aged ≥4 years) and workers in a San Francisco census tract (population: 5174) at outdoor, community-mobilized events over 4 days. We estimated SARS-CoV-2 point prevalence (PCR positive) and cumulative incidence (antibody or PCR positive) in the census tract and evaluated risk factors for recent (PCR positive/antibody negative) vs prior infection (antibody positive/PCR negative). SARS-CoV-2 genome recovery and phylogenetics were used to measure viral strain diversity, establish viral lineages present, and estimate number of introductions. RESULTS: We tested 3953 persons (40% Latinx; 41% White; 9% Asian/Pacific Islander; and 2% Black). Overall, 2.1% (83/3871) tested PCR positive: 95% were Latinx and 52% were asymptomatic when tested; 1.7% of census tract residents and 6.0% of workers (non-census tract residents) were PCR positive. Among 2598 tract residents, estimated point prevalence of PCR positives was 2.3% (95% confidence interval [CI], 1.2%-3.8%): 3.9% (95% CI, 2.0%-6.4%) among Latinx persons vs 0.2% (95% CI, .0-.4%) among non-Latinx persons. Estimated cumulative incidence among residents was 6.1% (95% CI, 4.0%-8.6%). Prior infections were 67% Latinx, 16% White, and 17% other ethnicities. Among recent infections, 96% were Latinx. Risk factors for recent infection were Latinx ethnicity, inability to shelter in place and maintain income, frontline service work, unemployment, and household income <$50 000/year. Five SARS-CoV-2 phylogenetic lineages were detected. CONCLUSIONS: SARS-CoV-2 infections from diverse lineages continued circulating among low-income, Latinx persons unable to work from home and maintain income during San Francisco's shelter-in-place ordinance.

Detection of a COVID-19 cluster by universal SARS-CoV-2 testing in a geriatric hospital and implications for infection control management.

Hospital-level COVID-19 testing strategies may require rapid changes depending on the dynamics of local epidemiology. A COVID-19 outbreak in a hospital near the authors' institution, a Geriatric Medicine centre in Berlin, Germany, prompted the implementation of comprehensive SARS-CoV-2 testing. Serial nasopharyngeal swabs were collected from all patients and staff and analysed for SARS-CoV-2 virus RNA using quantitative real-time PCR. In total, 11 of 84 patients (13.1%) and 1 of 147 employees (0.68%) tested positive. Of the 11 positive patients, 9 (81.8%) were asymptomatic at the time of testing. The data were used as the basis for adjusting local COVID-19 containment measures. Only one staff-to-staff transmission was observed, and there was no patient-to-patient, patient-to-staff or staff-to-patient transmission. Three patients infected with SARS-CoV2 died, two deaths being attributable to advanced malignant disease and one to COVID-19-associated myocarditis. In conclusion, universal SARS-CoV-2 testing revealed a cluster of predominantly asymptomatic infections, enabled appropriate local COVID-19 containment decisions and presumably contributed to the prevention of in-hospital SARS-CoV-2 transmission.

COVID-19 as an independent risk factor for subclinical placental dysfunction.

BACKGROUND: The pandemic of the severe acute respiratory distress syndrome-associated Coronavirus-2 (SARS-CoV-2) has affected millions around the world. In pregnancy the dangers to the mother and fetus are still being explored. SARS-CoV2 can potentially compromise maternal and neonatal outcomes and this may be dependent on the pregnancy stage during which the infection occurs. OBJECTIVE: The present study was done to find the histopathological alterations in the placenta of SARS-CoV-2 positive pregnancies with either no symptoms or mild coronavirus disease (COVID)-19 related symptoms and its association with neonatal outcomes. STUDY DESIGN: This was a prospective analytical study. Twenty seven asymptomatic or mildly symptomatic SARS-CoV-2 positive pregnant women with a singleton pregnancy delivered between 1st July 2020 and 15th September 2020, were included as cases. An equal number of SARS-CoV-2 negative singleton pregnancies matched for maternal and gestational age during the same period were included as controls. After delivery the histopathological examination of the placenta of these women was done and the findings recorded on a predesigned proforma based on the Amsterdam consensus criteria for evidence of maternal and fetal vascular malperfusion changes. RESULTS: The baseline characteristics were comparable between the cases and controls. The following features of maternal vascular malperfusion (MVM) were significantly higher in the placentae of COVID-19 positive pregnancies: retroplacental hematomas (RPH), accelerated villous maturation (AVM), distal villous hyperplasia (DVH), atherosis, fibrinoid necrosis, mural hypertrophy of membrane arterioles (MHMA), vessel ectasia and persistence of intramural endovascular trophoblast (PIEVT). Fetal vascular malperfusion (FVM) significantly associated with the positive pregnancies were chorioangiosis, thrombosis of the fetal chorionic plate (TFCP), intramural fibrin deposition (IMFD) and vascular ectasia. Additionally, perivillous fibrin deposition was also significantly higher in the placentae of cases. The percentage of spontaneously delivered women was comparable in the two groups. The sex and weight of the newborn and the number of live births were comparable between the two groups. CONCLUSIONS: Asymptomatic or mildly symptomatic SARS-CoV-2 positive pregnant women, with otherwise uncomplicated pregnancies, show evidence of placental injury at a microscopic level. Similar findings have been demonstrated in other studies too. This placental injury apparently does not lead to poor pregnancy outcomes. The extent of this injury in symptomatic cases of COVID-19 pregnancies and its consequences on the outcomes need to be analysed.