This study produced the first quantification of classical swine fever virus in air from infected pigs and in experimentally generated aerosols. The virus remained infectious in the aerosolized state for at least 30 minutes, with a half life between 4.5 and 15 minutes. Concentrations in cage air ranged from ten to the 0.3 to ten to the 1.6 TCID50 per cubic metre, and in expired air from ten to the 0.4 to ten to the 4.0.
Survival time in air is the variable that determines how far an airborne route can reach, and it is measured far less often than detection is. A half life of a few minutes constrains transmission to distances air can cover within a small multiple of that time, which is consistent with CSFV being placed in the short distance category, from zero to 150 metres, in the review by Hu and colleagues in 2023. The same research group applied the approach to African swine fever virus in 2013, and Nguyen and colleagues measured a comparable quantity for airborne E. coli in 2022, reporting a half life of 5.7 plus or minus 1.2 minutes.
The difference between a decay measurement and a distance measurement is worth keeping clear. A distance figure records where something was found on a particular day under particular weather. A half life describes a rate that applies wherever the organism travels, and it is the more transferable of the two. For a design decision, the distinction separates pathogens whose airborne risk is a matter of site geometry from those whose airborne risk extends to the neighbourhood.