Certain neurodegenerative diseases such as mad cow disease (bovine spongiform encephalopathy, BSE) and the human version vCJD (variant Creutzfeldt-Jakob disease) are caused by the misfolded proteins, prions. Prions act as a template for further misfolding and are transmitted through contaminated food, drink and bodily fluids.

Johannes Haybaeck and co-workers, University Hospital Zurich, Switzerland, have shown that airborne infection is also a route to transmission. They studied immunocompetent and immunodeficient mice, which were exposed to aerosols containing prion infected cells in an inhalation chamber. Both sets of mice became infected after a short exposure. The prions entered the brain via nerve endings in the nose without propagating or adapting further.

The team note that the conditions and level of infectivity leading to infection are unlikely to exist outside the lab. However, current biosafety guidelines for diagnostic and scientific laboratories or slaughterhouses should be revised to consider aerosols as a potential vector for prion infection.

• Aerosols Transmit Prions to Immunocompetent and Immunodeficient Mice
  J. Haybaeck, M. Heikenwalder, B. Klevenz, P. Schwarz, I. Margalith,et al.,
  PLoS Pathog. 2011, 7(1), e1001257.
  DOI: 10.1371/journal.ppat.1001257