First evidence of measles virus detected from exhaled breath in humans

Measles is among the most transmissible human infections, yet direct capture of measles virus from an infected person's exhaled breath has not been described. We assessed whether measles virus RNA can be detected from exhaled breath using facemask sampling (FMS).

We studied a 23-year-old unvaccinated woman with laboratory-confirmed measles (throat-swab RT-qPCR positive on day 5 post symptom onset). From day 10 post symptom onset, longitudinal sampling was performed for six consecutive days with duplicate specimens collected at each timepoint from the throat, face, cutaneous lesions and exhaled breath using a surgical mask fitted with polyvinyl alcohol sampling strips (FMS). Dissolved mask strips and swab eluates underwent RNA extraction followed by RT-qPCR targeting measles nucleoprotein and haemagglutinin genes, with human RNase P as a sample adequacy control. Quantification was derived from nucleoprotein-gene standards and normalised per strip or per 100 μL of swab eluate.

Measles virus RNA was consistently detected in exhaled breath captured by FMS and remained >10ˆ4 genome copies per sampling strip despite sampling beginning 10 days after symptom onset. During FMS collection, the participant reported no respiratory symptoms and did not vocalise. RNA kinetics differed by sampling site: throat and facial swabs increased even after complete rash resolution, whereas cutaneous-lesion swabs yielded comparatively low RNA levels. FMS kinetics diverged from throat swabs over time, suggesting distinct patterns of virus emission across compartments.

This study provides the first empirical evidence that measles virus RNA can be captured directly from the exhaled breath of an individual with measles. Although RNA detection does not confirm infectious virus, persistent high-level exhaled RNA supports FMS as a practical, non-invasive tool to study measles respiratory emission and may inform understanding of transmission and the duration of potential contagiousness. Empirical sampling of different respiratory compartments may help refine infection-prevention guidance during resurgent outbreaks.