Association between hepatitis C infection and other infectious diseases: a case for targeted screening?

Hepatitis C virus (HCV) shares risk factors and routes of transmission with several other infectious agents. However, the prevalence of comorbid infectious disorders among HCV-infected patients remains unknown. To analyze the association between HCV and several categories of infectious disorders, we carried out a case-control study using information from 172 hospitals contained in the computerized databases of the Department of Veterans Affairs.

We identified all HCV-infected patients who were hospitalized during 1992-1999. For each case, four control subjects without HCV were randomly chosen from hospitalized patients and were matched with cases on the year of admission. The frequencies of several predefined infectious disease diagnoses were compared between cases and control subjects, and the strength of these associations were assessed in multivariable logistic regression analyses.

We identified 34,204 HCV-infected patients (cases) and 136,816 control subjects without HCV. Patients in the case group were younger (48.4 yr vs 59.8 yr), were more frequently nonwhite (38.5% vs 26.5%), and were more likely to have served in Vietnam (68.1% vs 33.0%); all p < 0.0001. Compared with control subjects, patients with HCV had a significantly higher prevalence of other blood-borne virus infections, including HIV (14.1% vs 3.0%) and hepatitis B (22.4% vs 0.7%); immunodeficiency-related infections, including cytomegalovirus (0.6% vs 0.2%), toxoplasmosis (0.3% vs 0.1%), cryptococcosis (0.4% vs 0.1%), and tuberculosis (3.3% vs 1.3%); sexually transmitted diseases, including gonococcus (0.5% vs 0.1%), chlamydia (1.6% vs 0.7%), syphilis (2.0% vs 0.6%), and genital herpes (1.0% vs 0.3%); and bacterial infection, including peritonitis, sepsis, endocarditis, cellulitis, and carbuncles (all p < 0.0001). After excluding potentially immunocompromised patients, including those with HIV, organ transplant, and cirrhosis, HCV remained significantly associated with CMV, cryptococcus, tuberculosis, and sexually transmitted diseases. Similar results were obtained when the analyses were restricted to Vietnam-era veterans.

Several infectious diseases are more common among HCV-infected patients compared with those without HCV infection. These findings support an approach of targeted screening for HCV among patients with these infectious diseases.