SARS-CoV-2 and other respiratory pathogens are detected in continuous air samples from congregate settings.

Two years after the emergence of SARS-CoV-2, there is still a need for better ways to assess the risk of transmission in congregate spaces. We deployed active air samplers to monitor the presence of SARS-CoV-2 in real-world settings across communities in the Upper Midwestern states of Wisconsin and Minnesota. Over 29 weeks, we collected 527 air samples from 15 congregate settings and detected 106 SARS-CoV-2 positive samples, demonstrating SARS-CoV-2 can be detected in air collected from daily and weekly sampling intervals. We expanded the utility of air surveillance to test for 40 other respiratory pathogens. Surveillance data revealed differences in timing and location of SARS-CoV-2 and influenza A virus detection in the community. In addition, we obtained SARS-CoV-2 genome sequences from air samples to identify variant lineages. Collectively, this shows air surveillance is a scalable, cost-effective, and high throughput alternative to individual testing for detecting respiratory pathogens in congregate settings.

Viral sequencing reveals US healthcare personnel rarely become infected with SARS-CoV-2 through patient contact

BackgroundHealthcare personnel (HCP) are at increased risk of infection with the severe acute respiratory coronavirus 2019 virus (SARS-CoV-2). Between 12 March 2020 and 10 January 2021, >1,170 HCP tested positive for SARS-CoV-2 at a major academic medical institution in the Upper Midwest of the United States. We aimed to understand the sources of infections in HCP and to evaluate the efficacy of infection control procedures used at this institution to protect HCP from healthcare-associated transmission. MethodsIn this retrospective case series, we used viral genomics to investigate the likely source of SARS-CoV-2 infection in 96 HCP where epidemiological data alone could not be used to rule out healthcare-associated transmission. We obtained limited epidemiological data through informal interviews and review of the electronic health record. We combined viral sequence data and available epidemiological information to infer the most likely source of HCP infection. FindingsWe investigated 32 SARS-CoV-2 infection clusters involving 96 HCP, 140 possible patient contacts, and 1 household contact (total n = 237). Of these, 182 sequences met quality standards and were used for downstream analysis. We found the majority of HCP infections could not be linked to a patient or co-worker and therefore likely occurred in the outside community (58/96; 60.4%). We found a smaller percentage could be traced to a coworker (10/96; 10.4%) or were part of a patient-employee cluster (12/96; 12.5%). Strikingly, the smallest proportion of HCP infections could be clearly traced to a patient source (4/96; 4.2%). InterpretationInfection control procedures, consistently followed, offer significant protection to HCP caring for COVID-19 patients in a representative American academic medical institution. Rapid SARS-CoV-2 genome sequencing in healthcare settings can be used retrospectively to reconstruct the likely source of HCP infection when epidemiological data are not available or are inconclusive. Understanding the source of SARS-CoV-2 infection can then be used prospectively to adjust and improve infection control practices and guidelines. FundingThis project was funded in part through a COVID-19 Response grant from the Wisconsin Partnership Program at the University of Wisconsin School of Medicine and Public Health to T.C.F. and D.H.O. Author N.S. is supported by the National Institute of Allergy and Infectious Diseases Institute (NIAID) Grant 1DP2AI144244-01. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSOn 16 January 2021 we searched for "SARS-CoV-2" AND "healthcare workers" AND "viral sequencing" in Google Scholar. This search returned 57 results, and included a number of preprint articles. We found two studies that used viral sequencing to investigate healthcare-associated outbreaks in the Netherlands 1 and the United Kingdom 2. To our knowledge, no study has used viral sequencing to specifically investigate the source of SARS-CoV-2 infections in healthcare workers in the United States. Although we and others have written about the potential utility of sequencing as an infection control asset 3-6, few have demonstrated the practical application of such efforts. Added value of this studyOur study suggests infection control measures in place at the institution evaluated in this case series are largely protecting healthcare personnel (HCP) from healthcare-associated SARS-CoV-2 infections. Even so, the majority of healthcare-associated infections we did identify appeared to be linked to HCP-to-HCP spread so additional messaging and guidelines to reduce HCP-to-HCP spread in and out of the workplace may be warranted. In addition, we demonstrated how rapid viral sequencing can be combined with, even limited, epidemiological information to reconstruct healthcare-associated SARS-CoV-2 outbreaks. Implications of all the available evidenceHealthcare-associated SARS-CoV-2 infections negatively affect HCP, patients, and communities. Infections among HCP add further strain to the healthcare system and put patients and other HCP at risk. We found the majority of HCP infections appeared to be acquired through community exposure so measures to reduce community spread are critical. This further emphasizes the importance of mask-wearing, physical distancing, robust testing programs, and the rapid distribution of vaccines.

Fully automated detection and differentiation of pandemic and endemic coronaviruses (NL63, 229E, HKU1, OC43 and SARS-CoV-2) on the Hologic Panther Fusion

The Hologic Panther Fusion (PF) platform provides fully automated CE marked diagnostics for respiratory viruses, including recently SARS-coronavirus 2 by a transcription mediated amplification (TMA) assay, but not for the endemic human coronaviruses (hCoV). Therefore, a laboratory developed multiplexed RT-PCR protocol (LDT) that detects and differentiates the four hCoV NL63, 229E, HKU1 and OC43 was adapted on the PF. The novel CE marked Aptima SARS-CoV-2 TMA and the LDT for hCoV were validated with 321 diagnostic specimens from the upper and lower respiratory tract in comparison to two SARS-CoV-2 RT-PCRs (PF E-gene LDT and genesig RT-PCR, 157 specimens) or the R-GENE hCoV / hParaFlu RT-PCR (164 specimens), respectively. For the endemic hCoV, results were 96.3% concordant with two specimens discordantly positive in the PF and four specimens discordantly positive in the R-GENE assay. All discordantly positive samples had Ct values between 33 and 39. The PF hCoV LDT identified 23 hCoV positive specimens as NL63, 15 as 229E, 15 as HKU1 and 25 as OC43. The Aptima SARS-CoV-2 TMA gave 99.4 % concordant results compared to the consensus results with a single specimen discordantly positive. Moreover, 36 samples from proficiency testing panels were detected and typed correctly by both novel methods. In conclusion, the SARS-CoV-2 TMA and the LDT for hCoV enhanced the diagnostic spectrum of the PF for all coronaviruses circulating globally for a multitude of diagnostic materials from the upper and lower respiratory tract.

Optimizing direct RT-LAMP to detect transmissible SARS-CoV-2 from primary patient samples

SARS-CoV-2 testing is crucial to controlling the spread of this virus, yet shortages of nucleic acid extraction supplies and other key reagents have hindered the response to COVID-19 in the US. Several groups have described loop-mediated isothermal amplification (LAMP) assays for SARS-CoV-2, including testing directly from nasopharyngeal swabs and eliminating the need for reagents in short supply. Here we describe a fluorescence-based RT-LAMP test using direct nasopharyngeal swab samples and show consistent detection in clinically confirmed samples, albeit with approximately 100-fold lower sensitivity than qRT-PCR. We demonstrate that adding lysis buffer directly into the RT-LAMP reaction improves the sensitivity of some samples by approximately 10-fold. Overall, the limit of detection (LOD) of RT-LAMP using direct nasopharyngeal swab or saliva samples without RNA extraction is 1x105-1x106 copies/ml. This LOD is sufficient to detect samples from which infectious virus can be cultured. Therefore, samples that test positive in this assay contain levels of virus that are most likely to perpetuate transmission. Furthermore, purified RNA achieves a similar LOD to qRT-PCR. These results indicate that high-throughput RT-LAMP testing could augment qRT-PCR in SARS-CoV-2 screening programs, especially while the availability of qRT-PCR testing and RNA extraction reagents is constrained.

Initial evaluation of a mobile SARS-CoV-2 RT-LAMP testing strategy

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) control in the United States remains hampered, in part, by testing limitations. We evaluated a simple, outdoor, mobile, colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay workflow where self-collected saliva is tested for SARS-CoV-2 RNA. From July 16 to November 19, 2020, 4,704 surveillance samples were collected from volunteers and tested for SARS-CoV-2 at 5 sites. A total of 21 samples tested positive for SARS-CoV-2 by RT-LAMP; 12 were confirmed positive by subsequent quantitative reverse-transcription polymerase chain reaction (qRT-PCR) testing, while 8 were negative for SARS-CoV-2 RNA, and 1 could not be confirmed because the donor did not consent to further molecular testing. We estimated the RT-LAMP assays false-negative rate from July 16 to September 17, 2020 by pooling residual heat-inactivated saliva that was unambiguously negative by RT-LAMP into groups of 6 or less and testing for SARS-CoV-2 RNA by qRT-PCR. We observed a 98.8% concordance between the RT-LAMP and qRT-PCR assays, with only 5 of 421 RT-LAMP negative pools (2,493 samples) testing positive in the more sensitive qRT-PCR assay. Overall, we demonstrate a rapid testing method that can be implemented outside the traditional laboratory setting by individuals with basic molecular biology skills and can effectively identify asymptomatic individuals who would not typically meet the criteria for symptom-based testing modalities.

Distinct patterns of SARS-CoV-2 transmission in two nearby communities in Wisconsin, USA

Evidence-based public health approaches that minimize the introduction and spread of new SARS-CoV-2 transmission clusters are urgently needed in the United States and other countries struggling with expanding epidemics. Here we analyze 247 full-genome SARS-CoV-2 sequences from two nearby communities in Wisconsin, USA, and find surprisingly distinct patterns of viral spread. Dane County had the 12th known introduction of SARS-CoV-2 in the United States, but this did not lead to descendant community spread. Instead, the Dane County outbreak was seeded by multiple later introductions, followed by limited community spread. In contrast, relatively few introductions in Milwaukee County led to extensive community spread. We present evidence for reduced viral spread in both counties, and limited viral transmission between counties, following the statewide "Safer at Home" public health order, which went into effect 25 March 2020. Our results suggest that early containment efforts suppressed the spread of SARS-CoV-2 within Wisconsin.