The more outdoor air is pumped into office ventilation systems, the lower the inside levels of viruses that cause the common cold. Few studies have considered the possible link between the ventilation of buildings and respiratory illness in their occupants. Researchers from the Harvard School of Public Health in Boston, USA, sampled the workday air from three office buildings and used molecular techniques to detect and identify rhinoviruses in air samples and in nasal mucus from building occupants. The concentration of carbon dioxide in the air was used as a measure of exhaled breath and the supply rate of outdoor air. There was a significant relationship between the detection of airborne rhinoviruses and the amount of stale indoor air, the researchers found. Also, one rhinovirus present in a nasal mucus sample from an occupant with a cold proved to be identical to a rhinovirus collected on an air filter from the same building during the occupant's illness. The data suggests that lower ventilation rates and resulting increased carbon dioxide concentrations are associated with increased risk of exposure to potentially infectious droplets. Although the current study does not provide definitive proof that rhinovirus is transmitted through the aerosol route and is modulated by outdoor air supply rates, it does provide support for this hypothesis.
American Journal of Respiratory and Critical Care Medicine,
June 2004