SARS‐CoV‐2 detection in bioaerosols using a liquid impinger collector and ddPCR

The airborne route is the dominant form of COVID‐19 transmission, and therefore, the development of methodologies to quantify SARS‐CoV‐2 in bioaerosols is needed. We aimed to identify SARS‐CoV‐2 in bioaerosols by using a highly efficient sampler for the collection of 1–3 µm particles, followed by a highly sensitive detection method. 65 bioaerosol samples were collected in hospital rooms in the presence of a COVID‐19 patient using a liquid impinger sampler. The SARS‐CoV‐2 genome was detected by ddPCR using different primer/probe sets. 44.6% of the samples resulted positive for SARS‐CoV‐2 following this protocol. By increasing the sampled air volume from 339 to 650 L, the percentage of positive samples went from 41% to 50%. We detected five times less positives with a commercial one‐step RT‐PCR assay. However, the selection of primer/probe sets might be one of the most determining factor for bioaerosol SARS‐CoV‐2 detection since with the ORF1ab set more than 40% of the samples were positive, compared to <10% with other sets. In conclusion, the use of a liquid impinger collector and ddPCR is an adequate strategy to detect SARS‐CoV‐2 in bioaerosols. However, there are still some methodological aspects that must be adjusted to optimize and standardize a definitive protocol.