PMC:3265313 / 8061-13412 JSONTXT

{"project":"2_test","denotations":[{"id":"22312351-7365274-1233663","span":{"begin":449,"end":451},"obj":"7365274"},{"id":"22312351-11023724-1233664","span":{"begin":794,"end":796},"obj":"11023724"},{"id":"22312351-7365274-1233665","span":{"begin":899,"end":901},"obj":"7365274"},{"id":"22312351-2156469-1233666","span":{"begin":903,"end":905},"obj":"2156469"},{"id":"22312351-2999318-1233667","span":{"begin":995,"end":997},"obj":"2999318"},{"id":"22312351-16490124-1233668","span":{"begin":3901,"end":3903},"obj":"16490124"},{"id":"22312351-15709076-1233669","span":{"begin":3924,"end":3926},"obj":"15709076"},{"id":"22312351-16679182-1233669","span":{"begin":3924,"end":3926},"obj":"16679182"},{"id":"22312351-17307207-1233669","span":{"begin":3924,"end":3926},"obj":"17307207"},{"id":"22312351-16679182-1233670","span":{"begin":4935,"end":4937},"obj":"16679182"},{"id":"22312351-17307207-1233671","span":{"begin":4939,"end":4941},"obj":"17307207"},{"id":"22312351-16142653-1233672","span":{"begin":5116,"end":5118},"obj":"16142653"},{"id":"22312351-15709076-1233673","span":{"begin":5120,"end":5122},"obj":"15709076"},{"id":"22312351-16679182-1233673","span":{"begin":5120,"end":5122},"obj":"16679182"},{"id":"22312351-17307207-1233673","span":{"begin":5120,"end":5122},"obj":"17307207"},{"id":"22312351-16490124-1233674","span":{"begin":5127,"end":5129},"obj":"16490124"},{"id":"22312351-16369534-1233675","span":{"begin":5131,"end":5133},"obj":"16369534"}],"text":"4. Discussion\nViruses do not replicate outside living cell but infectious virus may persist on contaminated environmental surfaces and the duration of persistence of viable virus is affected markedly by temperature and humidity. Contaminated surfaces are known to be significant vectors in the transmission of infections in the hospital setting as well as the community. The role of fomites in the transmission of RSV has been clearly demonstrated [20]. Survival of viruses on a variety of fomites has been studied for influenza viruses, paramyxoviruses, poxviruses, and retroviruses [21]. The human coronavirus associated with the common cold was reported to remain viable only for 3 hours on environmental surfaces after drying, although it remains viable for many days in liquid suspension [13]. Parainfluenza and RSV viruses were viable after drying on surfaces for 2 and 6 hours, respectively [20, 22]. In aerosolised form, human coronavirus 229E is generally less stable in high humidity [12]. The environmental stability of SCoV was previously unknown and this information is clearly important for understanding the mechanisms of transmission of this virus in a hospital and community setting.\nIn the present study, we have demonstrated that SARS CoV can survive at least two weeks after drying at temperature and humidity conditions found in an air-conditioned environment. The virus is stable for 3 weeks at room temperature in a liquid environment but it is easily killed by heat at 56°C for 15 minutes [9]. This indicates that SARS CoV is a stable virus that may potentially be transmitted by indirect contact or fomites. These results may indicate that contaminated surfaces may play a major role in transmission of infection in the hospital and the community.\nOur studies indicate that SCoV is relatively more stable than the human coronaviruses 229E or OC43 and some other viral respiratory pathogens such as respiratory syncytial virus. These findings suggest that, while direct droplet transmission is an important route of transmission [23], the role of fomites and environmental contamination in virus transmission may play a significant role in virus transmission. In particular, fomites may contribute to the continued transmission of infection in the nosocomial setting that continues to occur in spite of the great attention and stringent precautions taken to prevent droplet spread. In addition to droplet precautions, reenforcing contact precautions and hand washing is called for.\nFaecal contamination of SCoV coronavirus may thus be an effective route of transmission of the disease. The outbreak in Amoy Garden in Hong Kong which affected over 300 residents in a single-apartment block with thought to have been transmitted by contaminated sewage. The stability of the virus on environmental surfaces and its presence in faeces indicates the potential that fecal contamination of fresh-food production may pose a threat for virus transmission; especially in countries with poor sanitation and sewage disposal systems and that studies to address this possibility are needed.\nIn this study, we showed that high temperature at high relative humidity has a synergistic effect on inactivation of SARS CoV viability while lower temperatures and low humidity support prolonged survival of virus on contaminated surfaces. The environmental conditions of countries such as Malaysia, Indonesia, and Thailand are thus not conducive to the prolonged survival of the virus. In countries such as Singapore and Hong Kong where there is a intensive use of air-conditioning, transmission largely occurred in well-air-conditioned environments such as hospitals or hotels. Further, a separate study has shown that during the epidemic, the risk of increased daily incidence of SARS was 18.18-fold higher in days with a lower air temperature than in days with a higher temperature in Hong Kong [24] and other regions [15–17]. Taken together, these observations may explain why some Asian countries in tropical area (with high temperature at high relative humidity) such as Malaysia, Indonesia, and Thailand did not have nosocomial outbreaks of SARS (Tables 1 and 2(a)–2(c)). It may also explain why Singapore, which is also in tropical area (Table 2(d)), had most of its SARS outbreaks in hospitals (air-conditioned environment). Interestingly, during the outbreak of SARS in Guangzhou, clinicians kept the windows of patient rooms open and well ventilated and these may well have reduced virus survival and this reduced nosocomial transmission. SARS CoV can retain its infectivity up to 2 weeks at low temperature and low humidity environment, which might facilitate the virus transmission in community as in Hong Kong which locates in subtropical area (Table 2(e)). Other environmental factors including wind velocity, daily sunlight, and air pressure, had shown to be associated with SARS epidemic, should also be considered [16, 17]. The dynamics of SARS epidemic involves multiple factors including physical property of virus, outdoor and indoor environments, hygiene, space, and genetic predispositions [10, 15–17, 24, 25]. Understanding the stability of viruses in different temperature and humidity conditions is important in understanding transmission of novel infectious agent including that of the recent influenza Apandemic H1N12009."}