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<p>This study helped to identify potential approaches to assist with the interpretation of norovirus RT-PCR results. The work involved a short critical literature review to identify:</p>
<ul>
<li>the methods currently used to detect norovirus in food, the environment and clinical samples</li>
<li>the methods in the pipeline or on the horizon</li>
<li>the methods or approaches that could be capable of distinguishing infectious and non-infectious norovirus</li>
<li>the methods or approaches capable of assessing the integrity of norovirus capsid or RNA as a surrogate for infectivity</li>
</ul>
<p>This review considered all detection and quantification methods, including molecular techniques. Each was critically assessed for their respective strengths, weaknesses and their capacity to distinguish between infectious and non-infectious norovirus particles. The levels of norovirus detected in food by RT-PCR are lower than those in clinical samples and this was taken into account in assessing the different approaches and options. Each approach identified was assessed for the feasibility of their use in routine laboratories and applicability to testing in real food systems. The review also identified research/knowledge gaps in this area and made recommendations for future work.</p>
<p>Background: The conclusion of the Second Study of Infectious Intestinal Disease in the Community (IID2 Study) confirmed a high burden of intestinal viral disease in the UK, particularly that caused by norovirus. Person-to-person spread is a key transmission route for norovirus, although food contaminated at source, or by infected food handlers, is also frequently associated with outbreaks of disease and probably sporadic cases. There are significant gaps in our knowledge of how norovirus is able to survive and remain infectious in food, and on surfaces in kitchens.</p>
<p>Current detection methods for norovirus use reverse transcriptase polymerase chain reaction (RT-PCR) to detect and estimate the titre of norovirus present in food or environmental samples. Enzyme-linked immunosorbent assay (ELISA) methods are also available but are considered to be less sensitive. While the molecular methods are able to detect and in some cases quantify the amount of norovirus RNA present, they do not provide information on whether or not the detected virus is capable of causing human infection or the degree of any degradation/damage to the RNA or capsid.</p>
<p>It is not possible to culture norovirus and other viruses (feline calicivirus, murine norovirus) tend to be used as surrogates for norovirus in in vitro studies. In the absence of human volunteer studies to assess infectivity, other approaches need to be explored to assist the interpretation of the findings from molecular-based testing of food and or the environment. It has been suggested that assessing the condition of the norovirus capsid might provide an indication of the degree of protection for norovirus RNA detected by RT-PCR. However, the applicability and practicality of this approach for food and environmental samples is likely to require further investigation. </p>