Vidyya Medical News Service
Volume 6 Issue 154 Published - 14:00 UTC 08:00 EST 2-Jun-2004 Next Update - 14:00 UTC 08:00 EST 3-Jun-2004
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Low outdoor air supply in buildings increases exposure risk to cold viruses

In contrast to prior studies showing that hand contact transmitted cold viruses, investigators who sampled air from 3 buildings over 20 months found that occupants in buildings with a low outdoor air supply appeared to be at increased exposure risk to infectious cold droplets from fellow workers through the building's ventilation system.

Researchers sampled air in 3 different office buildings from 9 a.m. to 5 p.m. each work day, detecting airborne viruses in 32 percent of air sampling filters in the offices, using molecular methods. The investigators said that their data demonstrated a significant positive relationship between frequency of virus detection in air filters and degree of building ventilation. Outdoor air levels were measured by carbon dioxide concentrations greater than 100 parts per million above the background level.

Consequently, the data suggested that lower ventilation rates and resulting higher carbon dioxide concentrations are associated with an increased risk of exposure to potentially infectious droplet nuclei from persons with colds.

In addition to the positive relationship associated with building ventilation and outside air, the researchers discovered that one rhinovirus from a nasal lavage taken from a volunteer with a cold contained an identical nucleic acid sequence similar to that in the building air sample collected during the week.

According to the researchers, cold viral respiratory infections are the most common infectious disease in the U.S., are associated with an annual cost of $25 billion in direct and indirect costs, cause excessive and inappropriate antibiotic prescribing, and lead to 20 million days of work loss each year. The study appears in the first issue for June 2004 of the American Journal of Respiratory and Critical Care Medicine.

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