Barriers to hepatitis C transmission within breathing systems: efficacy of a pleated hydrophobic filter.

It has been suggested that breathing circuits contaminated with body fluids may provide a route of nosocomial patient-to-patient transmission of the hepatitis C virus. Thus, a number of authorities have recommended the use of breathing circuit filters to minimize such risks. The present study sought to simulate a humidified breathing circuit and evaluate two different designs of breathing circuit filters to determine their efficacy in preventing passage of the hepatitis C virus. A hydrophobic pleated-membrane filter consistently prevented the passage of hepatitis C virus while a large-pore "electret" filter design was ineffective. We conclude that not all filter types are equally suited to preventing the passage of viruses and we therefore consider it essential that, if filters are intended to prevent the passage of named pathogens in a humidified breathing circuit, they should be evaluated in a similar experimental system to that described in order to prove their efficacy.