Ad14 Case Study
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First discovered in 1953, human adenoviruses (Ad) are globally distributed and responsible for outbreaks of respiratory disease, conjunctivitis and childhood illnesses. Different Ad species are also responsible for recurring outbreaks of acute respiratory disease. Adenovirus serotype 14 (Ad14) is an emerging adenovirus that was responsible for cases of respiratory infection at the Air Force's only recruit training center, Lackland Air Force Base in San Antonio, Texas, beginning in 2007. The 2007 outbreak alone cost the Air Force over 6,334 training days, $4.6 million, and multiple deaths. Conceptual MindWorks was contracted by the Air Force to conduct research to determine if the process for decontaminating recruit trainees’ gas masks (which were suspected of being a possible source of the outbreak) was sufficient.
Reaching the Solution
The main approach employed to generate the optimal neutralization conditions for Ad14 was a suspension test method in which known amounts of adenovirus were inoculated directly into tubes containing appropriate solutions of household bleach. At the conclusion of the various treatments performed on a known quantity of adenovirus, samples were taken from each tube and analyzed by a quantitative PCR assay, known as real-time PCR. The varying amounts of viral DNA detected were converted into genome equivalents of infectious viral particles, thereby quantitatively demonstrating the amount of virus that was neutralized by the bleach. Additionally, several experiments were conducted in an attempt to recover useful data from mask coupons inoculated with virus. Pieces of the gas mask were inoculated with known amounts of virus and then transferred to tubes containing detergent or bleach. These samples were analyzed in the same manner discussed above. In all experimental procedures, a recombinant Ad5 surrogate virus was utilized instead of Ad14 in order to minimize the dangers of exposure to personnel during the course of this investigation. The results from the suspension assays verified the efficacy (99.9999% inactivation) of using only bleach with a concentration of 257 ppm for 2 minutes, which was the concentration and exposure time used in the Air Force mask sanitization procedure. Results from the inanimate carrier tests, however, indicated that adenovirus with an organic soil load dried onto gas mask coupons and exposed to detergent alone or bleach alone, were not sufficient to inactivate the virus. The inanimate carrier tests indicated that a rinse step between the detergent and bleach steps effectively increased the quantity of adenovirus inactivated (99.88%) by this procedure.
Due to the results of this study, it was shown that the Air Force decontamination process did not adequately address a significant reduction of adenoviral infectivity. Furthermore, results from an experiment conducted to determine the effects of increased levels of detergent carryover into the bleach tank indicated the probable inefficacy of the sanitization process performed, due to inhibition of the bleach virucidal activity by excess detergent carryover. The results of this research effort prompted initiation of change, not only in the Air Force’s decontamination procedure, but also in the Marine’s, Navy’s, and Army’s training and operational decontamination procedures. This decontamination procedure can also be applied to a wider range of infectious agents, including those of biowarfare or bioterrorism.