Household Transmission of Influenza A Viruses in 2021-2022.

Importance: Influenza virus infections declined globally during the COVID-19 pandemic. Loss of natural immunity from lower rates of influenza infection and documented antigenic changes in circulating viruses may have resulted in increased susceptibility to influenza virus infection during the 2021-2022 influenza season. Objective: To compare the risk of influenza virus infection among household contacts of patients with influenza during the 2021-2022 influenza season with risk of influenza virus infection among household contacts during influenza seasons before the COVID-19 pandemic in the US. Design, Setting, and Participants: This prospective study of influenza transmission enrolled households in 2 states before the COVID-19 pandemic (2017-2020) and in 4 US states during the 2021-2022 influenza season. Primary cases were individuals with the earliest laboratory-confirmed influenza A(H3N2) virus infection in a household. Household contacts were people living with the primary cases who self-collected nasal swabs daily for influenza molecular testing and completed symptom diaries daily for 5 to 10 days after enrollment. Exposures: Household contacts living with a primary case. Main Outcomes and Measures: Relative risk of laboratory-confirmed influenza A(H3N2) virus infection in household contacts during the 2021-2022 season compared with prepandemic seasons. Risk estimates were adjusted for age, vaccination status, frequency of interaction with the primary case, and household density. Subgroup analyses by age, vaccination status, and frequency of interaction with the primary case were also conducted. Results: During the prepandemic seasons, 152 primary cases (median age, 13 years; 3.9% Black; 52.0% female) and 353 household contacts (median age, 33 years; 2.8% Black; 54.1% female) were included and during the 2021-2022 influenza season, 84 primary cases (median age, 10 years; 13.1% Black; 52.4% female) and 186 household contacts (median age, 28.5 years; 14.0% Black; 63.4% female) were included in the analysis. During the prepandemic influenza seasons, 20.1% (71/353) of household contacts were infected with influenza A(H3N2) viruses compared with 50.0% (93/186) of household contacts in 2021-2022. The adjusted relative risk of A(H3N2) virus infection in 2021-2022 was 2.31 (95% CI, 1.86-2.86) compared with prepandemic seasons. Conclusions and Relevance: Among cohorts in 5 US states, there was a significantly increased risk of household transmission of influenza A(H3N2) in 2021-2022 compared with prepandemic seasons. Additional research is needed to understand reasons for this association.

Forty Years of Molecular Diagnostics for Infectious Diseases.

Nearly 40 years have elapsed since the invention of the PCR, with its extremely sensitive and specific ability to detect nucleic acids via in vitro enzyme-mediated amplification. In turn, more than 2 years have passed since the onset of the coronavirus disease 2019 (COVID-19) pandemic, during which time molecular diagnostics for infectious diseases have assumed a larger global role than ever before. In this context, we review broadly the progression of molecular techniques in clinical microbiology, to their current prominence. Notably, these methods now entail both the detection and quantification of microbial nucleic acids, along with their sequence-based characterization. Overall, we seek to provide a combined perspective on the techniques themselves, as well as how they have come to shape health care at the intersection of technologic innovation, pathophysiologic knowledge, clinical/laboratory logistics, and even financial/regulatory factors.

Mobilizing an Institutional Research Enterprise to Support Pandemic Diagnostic Care.

CONTEXT.­: The COVID-19 pandemic has triggered a worldwide crisis that created unprecedented challenges for the health care system, including diagnostic laboratories that faced an ever-increasing demand for SARS-CoV-2 testing. OBJECTIVE.­: To share our experiences mobilizing a large-scale volunteer operation within a diagnostic laboratory in response to the COVID-19 crisis. In particular, during the early stages of the pandemic, research scientists at Vanderbilt University Medical Center were called upon to address challenges put forth by the rapid increase in testing demands. Volunteer scientists became a valuable resource to the clinical laboratory team after stay-at-home orders were in place and rapid diagnostic capabilities for COVID-19 were not yet widespread, thus necessitating significant manual laboratory analysis to support patient care. However, these volunteer efforts were not without challenges, including considerations around the licensure of clinical laboratory workers. Requirements can differ significantly between states and, in our case, were alleviated by an emergency gubernatorial decree. DATA SOURCES.­: We summarize these experiences here as an operational roadmap for other institutions that wish to leverage biomedical research staff in response to future emergencies. We include recruitment and organizational schemes, as well as results of a survey that details participant experiences and identifies strategies for optimization. Lastly, we present considerations around long-term hosting of clinical laboratory volunteers, beyond just the initial stages of an emergency. CONCLUSIONS.­: Through strategic implementation, scientists can provide diagnostic laboratories with invaluable support in times of need, while maintaining high clinical quality and regulatory compliance.

Ligation-based assay for variant typing without sequencing: Application to SARS-CoV-2 variants of concern.

BACKGROUND: COVID-19 prevalence has remained high throughout the pandemic with intermittent surges, due largely to the emergence of genetic variants, demonstrating the need for more accessible sequencing technologies for strain typing. METHODS: A ligation-based typing assay was developed to detect known variants of severe acute respiratory syndrome virus 2 (SARS-CoV-2) by identifying the presence of characteristic single-nucleotide polymorphisms (SNPs). General principles for extending the strategy to new variants and alternate diseases with SNPs of interest are described. Of note, this strategy leverages commercially available reagents for assay preparation, as well as standard real-time polymerase chain reaction (PCR) instrumentation for assay performance. RESULTS: The assay demonstrated a combined sensitivity and specificity of 96.6% and 99.5%, respectively, for the classification of 88 clinical samples of the Alpha, Delta, and Omicron variants relative to the gold standard of viral genome sequencing. It achieved an average limit of detection of 7.4 × 104 genome copies/mL in contrived nasopharyngeal samples. The ligation-based strategy performed robustly in the presence of additional polymorphisms in the targeted regions of interest as shown by the sequence alignment of clinical samples. CONCLUSIONS: The assay demonstrates the potential for robust variant typing with performance comparable with next-generation sequencing without the need for the time delays and resources required for sequencing. The reduced resource dependency and generalizability could expand access to variant classification information for pandemic surveillance.

Direct PCR with the CDC 2019 SARS-CoV-2 assay: optimization for limited-resource settings.

PCR-based diagnostics generally require nucleic acid extraction from patient specimens prior to amplification. As highlighted early in the COVID-19 pandemic, extraction steps may be difficult to scale during times of massive demand and limited reagent supply. Forgoing an extraction step, we previously reported that the N1 primer/probe-set of the widespread CDC COVID-19 assay maintains high categorical sensitivity (95%) and specificity (100%) with direct inoculation of viral transport media (VTM) into qRT-PCR reactions. In contrast, the N2 set demonstrated a prominent Ct delay and low sensitivity (33%) without extraction. In the current study, we have improved the performance of this modified CDC assay (in particular the N2 set) by incorporating N1/N2/RNase P multiplexing and dissecting the effects of annealing temperature, VTM interference, and inoculum volume. The latter two factors exerted a more prominent effect on the performance of N2 than N1, although these effects were largely overcome through elevated annealing temperature. This unextracted/multiplex protocol was evaluated with 41 SARS-CoV-2 positive and 43 negative clinical samples, demonstrating a categorical sensitivity of 92.7% and specificity of 100% versus the unmodified CDC methodology. Overall, this work offers a generalizable strategy to maximize testing capabilities for COVID-19 or other emerging pathogens when resources are constrained.

COVID-19 severity from Omicron and Delta SARS-CoV-2 variants.

The Omicron variant of SARS-CoV-2 achieved worldwide dominance in late 2021. Early work suggests that infections caused by the Omicron variant may be less severe than those caused by the Delta variant. We sought to compare clinical outcomes of infections caused by these two strains, confirmed by whole genome sequencing, over a short period of time, from respiratory samples collected from SARS-CoV-2 positive patients at a large medical center. We found that infections caused by the Omicron variant caused significantly less morbidity, including admission to the hospital and requirement for oxygen supplementation, and significantly less mortality than those caused by the Delta variant.

SARS-CoV-2 Testing of Aerosols Emitted During Pediatric Minimally Invasive Surgery: A Prospective, Case-Controlled Study.

BACKGROUND: The COVID-19 pandemic has presented significant safety concerns for healthcare providers, especially those performing aerosol-generating procedures. Several surgical societies issued early warnings that aerosols generated during minimally invasive surgery (MIS) could harbor infectious quantities of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). This study tested the hypothesis that MIS-aerosols contain SARS-CoV-2. METHODS: To evaluate SARS-CoV-2 presence in aerosols emitted during intracavitary MIS, children <18 years who required emergent MIS and were discovered to be SARS-CoV-2-positive were enrolled. Swabs were obtained from the port in-line with a filtered smoke evacuation system, the tubing adjacent to this port, the fluid collection chamber and filter, and the distal endotracheal tube (ETT). All swabs were analyzed for SARS-CoV-2 using quantitative reverse-transcription polymerase chain reaction. To evaluate viral distribution in tissues, fluorescence in situ hybridization for SARS-CoV-2 was performed on resected specimens. Outcomes were recorded, and participating healthcare workers were tracked for SARS-CoV-2 conversion. RESULTS: From July 1, 2020, to June 30, 2021, 11 children requiring emergent MIS were discovered preoperatively to be SARS-CoV-2 positive (median age: 14 years [5-17]). SARS-CoV-2 was detected only in ETT swabs and not in surgical aerosols or specimens. Median operative time was 56.5 minutes (IQR: 46-66), and postoperative stay was 21.2 hours (IQR: 1.97-57.57). No complications or viral eruption were recorded, and none of 63 healthcare workers tested positive for SARS-CoV-2 within 6 weeks. DISCUSSION: SARS-CoV-2 was detected only in ETT secretions and not in surgical aerosols or specimens among a pediatric cohort of asymptomatic patients having emergent MIS.

Diurnal Variation in SARS-CoV-2 PCR Test Results: Test Accuracy May Vary by Time of Day.

False negative tests for SARS-CoV-2 are common and have important public health and medical implications. We tested the hypothesis of diurnal variation in viral shedding by assessing the proportion of positive versus negative SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) tests and cycle time (Ct) values among positive samples by the time of day. Among 86,342 clinical tests performed among symptomatic and asymptomatic patients in a regional health care network in the southeastern United States from March to August 2020, we found evidence for diurnal variation in the proportion of positive SARS-CoV-2 tests, with a peak around 1400 h and 1.7-fold variation over the day after adjustment for age, sex, race, testing location, month, and day of week and lower Ct values during the day for positive samples. These findings have important implications for public health testing and vaccination strategies.

The first 1000 symptomatic pediatric SARS-CoV-2 infections in an integrated health care system: a prospective cohort study.

BACKGROUND: The spectrum of illness and predictors of severity among children with SARS-CoV-2 infection are incompletely understood. METHODS: Active surveillance was performed for SARS-CoV-2 by polymerase chain reaction among symptomatic pediatric patients in a quaternary care academic hospital laboratory beginning March 12, 2020. We obtained sociodemographic and clinical data 5 (+/-3) and 30 days after diagnosis via phone follow-up and medical record review. Logistic regression was used to assess predictors of hospitalization. RESULTS: The first 1000 symptomatic pediatric patients were diagnosed in our institution between March 13, 2020 and September 28, 2020. Cough (52 %), headache (43 %), and sore throat (36 %) were the most common symptoms. Forty-one (4 %) were hospitalized; 8 required ICU admission, and 2 required mechanical ventilation (< 1 %). One patient developed multisystem inflammatory syndrome in children; one death was possibly associated with SARS-CoV-2 infection. Symptom resolution occurred by follow-up day 5 in 398/892 (45 %) patients and by day 30 in 443/471 (94 %) patients. Pre-existing medical condition (OR 7.7; 95 % CI 3.9-16.0), dyspnea (OR 6.8; 95 % CI 3.2-14.1), Black race or Hispanic ethnicity (OR 2.7; 95 % CI 1.3-5.5), and vomiting (OR 5.4; 95 % CI 1.2-20.6) were the strongest predictors of hospitalization. The model displayed excellent discriminative ability (AUC = 0.82, 95 % CI 0.76-0.88, Brier score = 0.03). CONCLUSIONS: In 1000 pediatric patients with systematic follow-up, most SARS-CoV-2 infections were mild, brief, and rarely required hospitalization. Pediatric predictors of hospitalization included comorbid conditions, Black race, Hispanic ethnicity, dyspnea and vomiting and were distinct from those reported among adults.

Low In-School COVID-19 Transmission and Asymptomatic Infection Despite High Community Prevalence.

There is concern that in-person schooling during the coronavirus disease 2019 (COVID-19) pandemic will facilitate disease transmission. Through asymptomatic surveillance and contact tracing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we found low rates of asymptomatic SARS-CoV-2 infection and little in-school transmission of COVID-19 when physical distancing and masking strategies were enforced despite a high community prevalence of COVID-19.

COVID-19 diagnostics for resource-limited settings: Evaluation of "unextracted" qRT-PCR.

The coronavirus disease 2019 (COVID-19) pandemic has created a precipitous increase in the need for molecular diagnostics. Unfortunately, access to RNA extraction reagents can represent a bottleneck for quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR)-based methodologies, stemming from both extraordinary supply-chain stresses and the global reach of the virus into resource-limited settings. To provide flexible diagnostic options for such environments, we report here an "unextracted modification" for qRT-PCR using the Centers for Disease Control's (CDC's) widely utilized primers/probe sets for severe acute respiratory syndrome coronavirus 2 (N1/N2/N3 targeting viral nucleocapsid and RP-control targeting human RNase P). This approach replaces RNA extraction/purification with a heat-inactivation step of viral transport media (VTM), followed by direct inoculation-with or without VTM spin concentration-into PCR master mixes. Using derivatives of care from our clinical workflow, we compared traditional and unextracted CDC methodologies. Although some decrease in analytic sensitivity was evident (by higher Ct values) without extraction, in particular for the N2 primer/probe-set, we observed high categorical positive agreement between extracted and unextracted results for N1 (unconcentrated VTM-38/40; concentrated VTM-39/41), N3 (unconcentrated VTM-38/40; concentrated VTM-41/41), and RP (unconcentrated and concentrated VTM-81/81). The negative categorical agreement for N1/N2/N3 was likewise high. Overall, these results suggest that laboratories could adapt and validate unextracted qRT-PCR protocols as a contingency to overcome supply limitations, with minimal impact on categorical results.

Laboratory Diagnosis of COVID-19: Current Issues and Challenges.

The COVID-19 outbreak has had a major impact on clinical microbiology laboratories in the past several months. This commentary covers current issues and challenges for the laboratory diagnosis of infections caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In the preanalytical stage, collecting the proper respiratory tract specimen at the right time from the right anatomic site is essential for a prompt and accurate molecular diagnosis of COVID-19. Appropriate measures are required to keep laboratory staff safe while producing reliable test results. In the analytic stage, real-time reverse transcription-PCR (RT-PCR) assays remain the molecular test of choice for the etiologic diagnosis of SARS-CoV-2 infection while antibody-based techniques are being introduced as supplemental tools. In the postanalytical stage, testing results should be carefully interpreted using both molecular and serological findings. Finally, random-access, integrated devices available at the point of care with scalable capacities will facilitate the rapid and accurate diagnosis and monitoring of SARS-CoV-2 infections and greatly assist in the control of this outbreak.