Public Health Definitions for Hepatitis C Virus (HCV) Investigation

May 14, 2010

	Rose	Audubon
Number of Patients Tested	4065	1183
Number of Patients Not Tested	638	37
TOTAL	4703	1220
Number of Patients Negative	3996	1166
Number of Patients Positive	69	17
Positive Not Associated	44	13
Positive and epidemiologically linked	6	0
Positive and linked by viral sequencing	18	0
Positive/Indeterminate.	1	4
	69	17

The above hepatitis C lab results have been reported following the completion of the department's initial epidemiological investigation.  Viral sequencing results will not be available for weeks to months.  The above results have been classified to provide more specific information, as follows:

Patients Negative
Test negative for HCV (Hepatitis C Virus). NOTE: This represents negative test results reported to the health department as a result of this investigation. Laboratories are not required to report negative results.

Patients Positive / not associated
Indicates a positive HCV test, but determined not to be associated with exposure to former employee through epidemiologic investigation or laboratory testing. This includes patients with previous positive HCV tests, patients with genotypes other than 1b, and patients whose blood was sequenced but whose hepatitis C virus was not highly related to the virus isolated from the infected healthcare worker.

Positive and epidemiologically linked
Indicates a positive HCV test, and determined to be epidemiologically associated with exposure to former employee. This includes patients without genotype testing and those with genotype 1b. It does not include individuals for whom viral sequencing was performed.

Positive and linked by epidemiology and viral sequence analysis
Indicates a positive HCV test, determined to be epidemiologically associated with exposure to former employee, and the virus was found to be highly related to that of the former employee by viral sequence analysis. [NOTE: All viral sequencing results are not completed.]

Patients whose lab results for hepatitis C were genotype 1b are listed as "positive associated."  Lab results that come back in this category (genotype 1b) are sent for further "sequencing" testing, as are other tests that are positive for hepatitis C RNA.  The more extensive sequence testing and analysis is then performed to determine if the virus isolated from specimens obtained from patients is related to the virus isolated from the infected healthcare worker. The degree of relatedness (or similarity) between specimens sent to CDC for this investigation will be compared and expressed as a percent. If this degree is very high (approaching 100%) - and if all the other facts of the case fit with transmission -  it is interpreted as a transmission link between the patient's virus specimen and the health care worker's virus specimen.

Positive / indeterminate
Indicates a positive HCV test, but genotyping and sequencing could not be performed and patient had other risk factors for hepatitis C. Available laboratory and epidemiologic data is insufficient to associate infection with exposure from former employee.

NOTE:  Positives will not be reported until initial epidemiologic investigation is complete.