Intervention methods to control the transmission of noroviruses and other enteric and respiratory viruses

<strong>Intervention methods to control the transmission of noroviruses and other enteric and respiratory viruses</strong> <strong>Era Tuladhar</strong> Abstract Human noroviruses are the leading cause of acute and outbreak associated gastroenteritis worldwide. The outbreaks occur often in hospitals, nursing homes, health care centers as well as in individual homes. Due to the high number of outbreaks and frequency of infection, the burden of disease is high. The virus transmission takes place from person to person directly through the fecal oral route or indirectly through contaminated surfaces or consumption of contaminated food. This study aimed to investigate methods to reduce the burden of disease caused by norovirus and focuses on reducing the transmission through hands and contaminated surfaces. Besides human norovirus, other enteric and respiratory viruses are also transmitted through these routes and were included in the study. Enteric viruses included in the study were human norovirus GI.4 and GII.4, poliovirus Sabin1, rotavirus SA11, parechovirus 1 and murine norovirus 1 (MNV1). The respiratory viruses were adenovirus type 5 and influenza A (H1N1) virus. These viruses can contaminate food through food handler-related contamination. Heating and pasteurizing is a commonly used method for inactivation of microorganisms in food. Heating at commonly used temperatures of 56°C and 73°C showed that thermo-stability of parechovirus and influenza virus was found to be similar to that of proven foodborne viruses and heating at 73°C for 3 min is sufficient to reduce the infectivity of the tested viruses > 4 log10. Not only food, contaminated hands can also transfer viruses to different surfaces, which are then sources of further transmission of the viruses. Cleaning and disinfection of contaminated surfaces are common intervention methods used in health care and kitchen facilities. The enteric and respiratory viruses showed varying susceptibility to cleaning and disinfection procedures applied. Data on infectious doses and transfer efficiencies was used to estimate a target level to which the residual contamination should be reduced and it was found that a single wipe with liquid soap followed by a wipe with 250 ppm free chlorine solution was sufficient to reduce the residual contamination to below the target level for most of the pathogens tested. Spot disinfection by 1000 ppm chlorine solution after wiping with liquid soap was sufficient to reduce the genomic copies of human norovirus GI.4 and GII.4 (> 5 log10 PCRU) completely within 10 min. In addition to manual cleaning and disinfection, non-touch disinfection of contaminated surfaces by vaporized hydrogen peroxide disinfection at 127 ppm for 1 h, as approved disinfection in the Netherlands for hospitals and health care centers, is effective against poliovirus Sabin 1, rotavirus SA11, adenovirus type 5 and MNV1 on stainless steel, framing panel (> 4 log10 infectivity reduction) and gauze (> 2 log10 infectivity reduction). Beside non-touch disinfection, immobilized biocidals have been tested for disinfection of contaminated surfaces. Immobilized quaternary ammonium compound coatings were virucidal against the influenza virus within 2 min but no virucidal effect against poliovirus was found in 6 h. Thus the coating can be used against the influenza A virus to prevent the transmission through frequently touched sites but not for non-enveloped viruses. Our study demonstrated that a norovirus contaminated hand can transfer the viruses to different surfaces, including food, even after the virus is dried. As an intervention method to prevent the transmission of the virus, washing hands with soap and water (> 5 log10 PCRU reduction) is better than using alcohol based hand disinfectants in removing noroviruses from hands. This research has delivered new insights in methods to reduce transmission of human norovirus and produced comparative quantitative data on intervention methods to control transmission of other enteric and respiratory viruses. The study has additionally contributed to a better understanding of human norovirus transmission intervention efficiency. The new insights allow for the development of science based guidelines to control norovirus and other enteric and respiratory viruses in outbreak settings and thus help to reduce the burden of illness caused by these viruses.