Norovirus Infection

How is a norovirus infection diagnosed?

Because the symptoms of norovirus are similar to those of other common viral diarrheas like rotavirus, it is necessary to do specific tests to identify the virus. Norovirus cannot be cultured in a laboratory. However, the RNA inside the virus may be detected directly using polymerase chain reaction (PCR) tests, and these tests are the ones that are most commonly used. Enzyme-based immunoassays (EIA) can also be used to detect the virus in stool samples. EIAs use special antibodies that attach to virus particles. In addition, the Ridascreen Norovirus 3rd Generation EIA assay is approved for use to detect norovirus when a number of people have simultaneously contracted gastroenteritis and there is a clear avenue for virus transmission, such as a shared location or food source. However, this new test is not sensitive enough for definitive diagnosis of norovirus infection in an individual. The human body makes antibodies against norovirus, and these can be identified with immunoassay testing of blood samples. Unfortunately, it takes 10-14 days for the body to make antibodies, so this test is not useful for real-time diagnosis. It is also possible to see the virus particles using electron microscopy, although this is mostly a research tool. Currently, the preferred test for norovirus according to the CDC is the PCR test. This test helps distinguish between other diseases (for example, rotavirus and Salmonella infections) that may produce similar symptoms.

Once norovirus has been confirmed in an outbreak setting, it is not necessary to test every person. Rather, people with typical symptoms are assumed to have acquired the virus. Continue Reading

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Reviewed on 10/28/2015
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