Inactivation of airborne SARS-CoV-2 by thyme volatile oil vapor phase

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a global pandemic mainly through air transmission. Novel variants are emerging and thus innovative methods of air disinfection still warrant exploration. Essential oils with virucidal properties may be an alternative to known air disinfectants.

Analysis of virucidal potential of thyme oil vapor phase against airborne SARS-CoV-2.

Chemical composition of thyme oil was analyzed by Gas chromatography-mass spectrometry.Thyme oil was tested in solution in different dilutions against soluble SARS-CoV-2. For air disinfection analysis, different volumes of thyme oil were placed in a container with hot water and its vapor phase was tested against airborne/aerosolized SARS-CoV-2 in a 30 m³ room. The aerosolized virus was collected in a gelatine filter using a vacuum system after the test and the collected virus was quantified utilizing inoculations of serial dilutions into 96-well plates with VERO E6 cells.

The main component of thyme oil was carvacrol. Thyme oil had virucidal action both in solution and in the air. Thyme oil at 1/1000 dilution (volume/volume, final concentration) in a solution eliminated more than 99,99% of SARS-CoV-2 in the solution in 60 min. In air disinfection tests in 30 m³ room, vapor phase of 40 ml of extracted thyme oil eliminated more than 99,99% (>4 LOG₁₀) of airborne SARS-CoV-2, and vapor phase of 20 ml of thyme oil resulted in elimination of 90,88% (1,04 LOG₁₀) airborne SARS-CoV-2 in 60 min.

We have shown that vapor phase of thyme oil inactivates more than 99,99% of airborne SARS-CoV-2 in a room for the first time to the best of our knowledge. This finding may have implications on the use of thyme oil as a potential air disinfectant against SARS-CoV-2.