Airborne severe acute respiratory syndrome coronavirus and its implications.

Airborne transmission of the severe acute respiratory syndrome (SARS) coronavirus (CoV) has been the favored explanation for its transmission on an aircraft [1] and appeared to explain a large community outbreak of SARS in the Amoy Gardens in Hong Kong [2]. The article by Booth et al. in this issue of the Journal of Infectious Diseases [3] suggests that airborne dissemination of SARS-CoV may also occur in the health-care setting. A patient with SARS who was breathing quietly but coughing occasionally in a hospital room contaminated the surrounding air with SARS-CoV, as shown by experiments conducted during the SARS outbreak in Can-ada in early 2003. Several viruses and other pathogens, such as Mycobacterium tuberculosis, have been shown to be transmitted by airborne dissemination [4–8]. However, the possibility of airborne dissemination of SARS-CoV has been controversial. The important work by Booth et al. has shown beyond doubt that SARS-CoV aerosol generation can occur from a patient with SARS. The study was well conceived and designed and employed nucleic acid amplification and state-of-the-art air slit-sampling technology. To ensure the accuracy of their results, the authors followed stringent control measures in their studies. For example, empty specimen containers made the same trip from outside to the hospital ward and then to the laboratory , in the same way as the real specimen containers. All samples were tested similarly, and the technologists were blinded to their true nature. These procedures helped to control for possible contamination of the outside of the specimen containers, a little-thought-of possible cause of false-positive test results. Another , even more stringent measure was the dedication of special rooms for these experiments. These researchers anticipated laboratory contamination as a possible cause of false-positive results long before news broke of SARS-CoV escaping microbiology laboratories through infection of workers [9, 10]. Other measures, such as use of dummy controls (with water only), confirming the identity of SARS-CoV by testing more than one region of the viral genome, and sequencing the amplified products, add to the credibility of their results. The authors use their findings to make several valid recommendations regarding proper ventilation, air filtration, and aerosol prevention. Because none of the SARS-CoV cultures were found to be positive and host infection was not involved, the authors rightly avoided drawing a conclusion of airborne transmission of SARS-CoV. Definitive proof of transmission will need to come from experiments similar to those performed by Riley …