Detection of SARS-CoV-2 infection by saliva and nasopharyngeal sampling in frontline healthcare workers: an observational cohort study

Abstract

Background The SARS-CoV-2 pandemic has caused an unprecedented strain on healthcare systems worldwide, including the UK National Health Service (NHS). During the first wave of SARS-CoV-2 transmission in UK, SARS-CoV-2 NHS diagnostic test availability was limited to self-isolating symptomatic staff. The burden of symptomatic and asymptomatic infection in healthcare workers (HCW) attending work was unknown. Methods We conducted an observational cohort study of SARS-CoV-2 infection in HCW working in an acute NHS Trust during the first wave of the COVID-19 pandemic, using serial self-collected saliva and nasopharyngeal (NP) samples. We also collected self-assessed symptom profiles and isolation behaviours. We retrospectively compared SARS-CoV-2 detection by RT-PCR from saliva (weekly) and NP swabs (twice weekly) from 85 individuals in this cohort and evaluated the association with symptoms. Findings Over a 12-week period from 30th March 2020, 40% (n=34/85, CI95% 31.3-51.8%) HCWs had evidence of SARS-CoV-2 infection by surveillance NP swab and/or saliva RT-qPCR. Agreement between paired saliva and NP swabs was poor (28.6%, CI95% 13.2-48.7%) with both methods detecting symptomatic and asymptomatic infections. Symptoms were reported by 47.1% (n=40) and self-isolation by 25.9% participants (n=22). Only 41.2% (n=14/34) participants with SARS-CoV-2 infection reported any symptoms within 14 days of the infection. Interpretation HCWs are a potential source of SARS-CoV-2 transmission in hospitals and symptom screening will identify the minority of infections in HCW. Saliva is an easily accessible fluid sample for screening for SARS-CoV-2 infection and in addition to NP swab, facilitated ascertainment of symptomatic and asymptomatic cases in this setting. Combined saliva and NP testing would improve detection of SARS-CoV-2 for surveillance. Better understanding of transmissibility from asymptomatic staff using transmission-based infection precautions, is required to inform policy.

Streptococcus pneumoniae colonization associates with impaired adaptive immune responses against SARS-CoV-2

“…Participants were screened for both SARS-CoV-2 and Spn presence in the naso/oropharynx ( Figure 1A ). Among HCWs, 34% (29 of 85) tested positive for SARS-CoV-2 at any time point during the 3-month follow-up period of the study on a combined nose and throat (NT) swab or on NT swab and saliva sample, and all of these HCWs experienced asymptomatic or mildly symptomatic viral infection ( 20 ). In the patient cohort, 63.5% (255 of 400) tested positive for SARS-CoV-2 at the time of recruitment to the study on the basis of NT swabs, and their symptoms ranged from moderate to severe ( 21 ).…”

“…Screening against SARS-CoV-2 and Spn was performed on NT swabs and saliva samples ( Figure 1A ). Symptom reporting was done via a questionnaire completed twice weekly, accompanying each sampling episode ( 20 ).…”