LB-11 - Comparison of Viral Loads in Individuals With or Without Symptoms At Time of COVID-19 Testing Among 32,480 Residents and Staff of Nursing Homes and Assisted Living Facilities in Massachusetts

Background: Transmission of COVID-19 from people without symptoms confounds public health containment strategies. Comprehensive cross-sectional screening enables assessment of viral load independent of symptoms, informing transmission risks. We quantified SARS-CoV-2 burden by RT-qPCR from comprehensive screening of nursing homes and assisted living facilities in Massachusetts to inform our ability to detect SARS-CoV-2 in individuals with or without symptoms.

Methods: From 4/9/20 to 6/9/20, we tested nasopharyngeal (NP) swabs from 32,480 unique individuals comprising staff and residents of the majority of nursing homes and assisted living facilities in Massachusetts. Symptomatology at the time of sampling and demographic information were provided by each facility. NP swabs were collected, RNA extracted, and SARS-CoV-2 testing performed by RT-qPCR. We compared cycle thresholds (Ct) with a standard curve to quantify viral loads.

Results: The nursing home and assisted living facilities resident cohort (N = 16,966) was 65% female with mean age 82. The staff cohort (N = 15,514) was 76% female with mean age 45. In all, 2654 residents (15.5%) and 624 staff (4.1%) tested positive for SARS-CoV-2, including 12.7% of residents and 3.7% of staff without symptoms, compared to 53.1% of residents and 18.2% of staff with symptoms. The Ct distributions for viral probes were very similar between populations with and without symptoms (Fig 1), with a statistically but not meaningfully different mean (ΔCt 0.71 cycles, p = 0.006) and a similar range (12-38 cycles). This similarity persisted across all sub-categories examined (age, race, ethnicity, sex, resident/staff).Figure 1


Conclusion: In a large cohort of individuals screened for SARS-CoV-2 by RT-qPCR, we found strikingly similar viral load distributions in patients with or without symptoms at the time of testing. The size of the study population, including both staff and residents spanning a wide range of ages, provides a comprehensive cross-sectional point prevalence measurement of viral burden. Because the distributions of viral loads are very similar regardless of symptoms, existing testing modalities validated for detection of SARS-CoV-2 RNA in symptomatic patients should perform similarly well in individuals without symptoms at the time of testing.

Presenter and Author(s)

• 

  Roby P. Bhattacharyya, MD, PhD

  Assistant Professor
  Massachusetts General Hospital
  Boston, MA

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

  Slides

Co-Author(s)

• NL

  Niall J. Lennon, PhD

  Senior Director, Translational Genomics
  Broad Institute
  Cambridge, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• MM

  Michael Mina, MD, PhD

  Assistant Professor
  Harvard School of Public Health
  Boston, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• HR

  Heidi L. Rehm, PhD

  Professor
  Massachusetts General Hospital
  Boston, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• DH

  Deborah T. Hung, MD, PhD

  Professor
  Harvard Medical School
  Boston, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• SS

  Sandra Smole, PhD

  Director
  Massachusetts State Public Health Laboratory
  Boston, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• AW

  Ann E. Woolley, MD, MPH

  Attending Physician
  Brigham and Women's Hospital
  Boston, MA

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• EL

  Eric Lander, PhD

  Institute Director
  Broad Institute
  Cambridge, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
• SG

  Stacey Gabriel, PhD

  Senior Director, Genomics Platform
  Broad Institute
  Cambridge, Massachusetts

  Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.