Breath-, air- and surface-borne SARS-CoV-2 in hospitals.
Level 4 - case-series / case-control
Cross-sectional observational sampling study of patients and hospital environments
PubMed 33078030 · doi:10.1016/j.jaerosci.2020.105693
What was done
Researchers collected exhaled breath condensate, environmental air samples, and surface swabs across four hospitals in Wuhan with natural ventilation and regular disinfection. The study evaluated 14 participants (including 10 COVID-19 patients) using RT-PCR and digital PCR to assess SARS-CoV-2 contamination and evaluate patients meeting standard throat-swab discharge criteria.
What was found
Among COVID-19 patients ready for discharge based on standard protocols, 22.2% (n = 9) had detectable SARS-CoV-2 RNA in their exhaled breath (~10^5 RNA copies/m^3, estimated at ~1400 RNA copies/min). Surface swabs were positive in 3.1% (n = 318), showing contamination on healthcare worker face shields and work shift floors (3–8 viruses/cm^2). Air samples were positive in 6.8% (3 of 44, concentration 9–219 viruses/m^3) under natural ventilation conditions (1.6–3.3 m/s).
Why it matters
Standard throat-swab testing protocols may miss patients who continue shedding viral RNA into the air via respiration. Testing exhaled breath condensate could provide an additional safeguard prior to hospital discharge.
Limits
The human sample size was extremely small (10 COVID-19 subjects, 9 evaluated at discharge). PCR detects RNA presence rather than viable infectious virus, and clinical transmission outcomes following discharge were not evaluated.
Cited by
- supports Air sampling studies in Chinese hospital wards with COVID-19 patients found almost undetectable levels of SARS-CoV-2 in the air, but detected viral material on air conditioning grates and filters.