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Katerine Aldrige
One important area of norovirus research is finding ways of inactivating the virus on hands, foods, and surfaces so that it cannot cause disease. Think about the common places norovirus turns up, such as schools, hospitals, restaurants, and other areas where lots of people gather, and it is easy to see why having effective disinfection methods are important. Norovirus is also known for being particularly hard to get rid of, and many of the common disinfectants and sanitizers have not been shown to be effective against the virus.
There are several methods we currently use to inactivate norovirus, such as through the use of heat, changes in pH, ultraviolet light, high pressure, and chemicals like alcohols and chlorine bleach. However, the all-important caveat is that we have been unable to propagate norovirus in cell culture, meaning we have not been able to directly examine what these things do to the virus, and whether they render the virus unable to infect someone.
We have instead turned to the next best thing, which is studying other related viruses that we can culture, and use them to make inferences about the human version. Some of the common surrogate viruses include feline calicivirus (FCV) in cats, murine norovirus (MNV) in mice, porcine enteric calicivirus (PEC) in pigs, and Tulane virus (TuV) in rhesus macaques. FCV has been a classic stand-in for norovirus because we have been able to culture it for decades. MNV is a newer choice, discovered in 2003, and is genetically closer to norovirus than FCV. Newer still is TuV, and it and PEC have been gaining a lot of attention in recent years.
Unfortunately, the different surrogates perform differently when exposed to the various inactivation methods, muddying the waters when it comes to comparing them to human noroviruses. For example, FCV is inactivated at a pH of 2, while MNV and TuV are not, and norovirus is similarly resistant to low pH. Compared to the other four surrogates, FCV is the most susceptible to changes in pH, chlorine bleach, and high pressure. This does not mean FCV does not have its place in research, because no one surrogate is the best choice for all tests. For example, MNV is more susceptible to alcohols than the other viruses, including norovirus. On the whole, MNV and TuV are the most resistant to inactivation methods, making them the conservative way to go when testing ways of inactivating norovirus.