Delaware Public Health Laboratory Norovirus Policy Re: Norovirus Testing

NOROVIRUS REAL-TIME POLYMERASE CHAIN REACTION (PCR) TESTING

At the Delaware Public Health Laboratory (DPHL), the RNA of the virus is first extracted from stool specimens. Then, a complementary DNA strand is made using the RNA from the virus as a template and Real-Time PCR is performed to amplify the product. Real time PCR utilizes a fluorescent probe that gives off a light signal every time a copy of the target sequence is produced. This signal is read by an instrument and represented graphically on a computer. This method allows for the user to obtain data while the run is in progress. In the case of norovirus, probes are designed to be genogroup specific which allows not only for real time, data, but also differentiation of the virus into a specific genogroup based on the probe that registers.

SPECIMEN SUBMISSION

DPHL tests for norovirus during outbreaks and/or disease cluster situations, but not for individual cases. When multiple cases (more than 2) of enteric diseases are suspected in day care centers, nursing homes, restaurants or places of high risk, the facility or nursing director should notify the Bureau of Epidemiology (EPI) of the Division of Public Health to ensure that the event is appropriate for investigation. Foodborne illnesses may also be reported by families, schools, organizations, etc., to either the Foodborne Epidemiologist or the Office of Food Protection (OFP). OFP should be notified when restaurant or institution associated illness is suspected.

After approval by EPI, a specimen for each patient should be submitted and norovirus testing requested. Specimen collection kits for collection of stool are available from the DPHL. Each specimen must be clearly labeled with the patient's name and date of birth and accompanied by a Test Requisition Form. Please follow all relevant Laboratory Specimen Collection Procedures. Unlabeled specimens will not be tested. The Bureau of Epidemiology will determine how many specimens to collect, from what units, etc. based on the nature of the cluster. Generally, specimens from 3 to 5 patients are recommended for testing. Once positive specimens are obtained from a cluster, testing of additional patients is considered unnecessary. Specimen collection for viral testing should begin as soon as an outbreak is suspected. Ideally, specimens should be collected during the acute phase of the illness while the stools are still liquid or semi-solid. While stool specimens are preferred, emesis specimens are also acceptable. Specimens should be kept refrigerated at 4 degrees C until they can be tested (freezing can destroy virus particles).

RESULT REPORTING

Norovirus testing will be performed within 1-2 business days of receipt. The results will be reported for a positive norovirus test as "Nucleic Acid Detected" and for a negative norovirus test as "No Nucleic Acid Detected." The Bureau of Epidemiology and the submitting facility will be notified of the results via telephone, fax, or email, and the official report will be forwarded to Epidemiology and recorded on the Laboratory Information Management System (LIMS).

Return to Delaware Public Health Laboratory page.

Please note: Some of the files available on this page are in Adobe PDF format which requires Adobe Acrobat Reader. A free copy of Adobe Acrobat Reader can be downloaded directly from Adobe . If you are using an assistive technology unable to read Adobe PDF, please either view the corresponding text only version (if available) or visit Adobe's Accessibility Tools page.