Viruses

In the past, viruses were considered nonliving infectious particles, little more than genetic material wrapped in a protein capsid. Today, virologists are beginning to think of viruses as living organisms that can be classified phylogenetically into defined species, much like any other living organism. The primary reasons for this shift in attitude can be partially attributed to the discovery of giant viruses, having large genomes and complex regulatory systems. Aside from that, it has become obvious that viruses lead complex lives; they evolve, speciate, and participate in the evolution of all classes of living organisms. In this chapter, we will discuss the early attempts to classify viruses, and review the biologic properties of the classes of virus that contain human pathogens.

A population-based study of hepatitis D virus as potential risk factor for hepatocellular carcinoma

Hepatitis D virus (HDV) is dependent on the presence of hepatitis B virus (HBV) for transmission and replication because of its inability to produce its own coat. It remains unclear whether HDV infection increases the risk of hepatocellular carcinoma. Using the Swedish Hospital Discharge Register and Outpatient Registry, we identified 9160 patients with chronic HBV infection between 1997 and 2008, of whom 327 had chronic HDV infection and 323 had acute HDV infection. Standardized incidence ratios (SIRs) were calculated for these patients compared with the general population. The risk of hepatocellular carcinoma was greatly increased in patients with HBV and HDV (SIR = 137.17, 95% confidence interval [CI] = 62.19 to 261.51). The risk of hepatocellular carcinoma among patients with HBV and HDV was increased (SIR = 6.11, 95% CI = 2.77 to 11.65) when patients with chronic HBV infection alone were used as the reference population. Similar results were observed for patients with chronic HDV infection (SIR = 99.26, 95% CI = 42.39 to 196.55). Our findings indicate that HDV is a strong risk factor for hepatocellular carcinoma.

Prevalence of hepatitis delta virus (HDV) infection in chronic hepatitis B patients in eastern Turkey: still a serious problem to consider

Hepatitis delta virus (HDV) is a serious cause of liver-related morbidity and mortality. Coexistent infection with HDV tends to aggravate the course of hepatitis B virus (HBV)-associated liver disease. The aim of this study was to determine the prevalence of HDV infection among patients chronically infected with HBV in the Elazig region, which is in eastern Turkey. A group of 282 patients infected with chronic HBV were investigated for the study. Anti-HDV seropositivity was evaluated in all patients. The anti-HDV-positive patients were further tested for HDV RNA. Severity of liver disease was assessed by liver biopsy. Regression analysis was used to determine the relationship between independent variables and HDV positivity. Of 282 chronic HBV patients, 192 were men (68.1%) and 90 were women (31.9%). The mean age was 43.8 ± 12.7 (between 18 and 73 years). Anti-HDV was positive in 45.5% of the patients (128/282). Among the 128 anti-HDV-positive patients, 116 were checked for HDV RNA and 56.9% were found positive (66/116). Chronic HDV infection rate was therefore present in at least 23.4% of the whole study group (66/282). There were 83 patients with cirrhosis (29.4%) in the study group. Anti-HDV seroprevalence and HDV RNA presence were higher in those with cirrhosis (61.4% and 42.2%, respectively). No significant relationship was found between anti-HDV seropositivity and demographic factors such as age, sex and operation or transfusion history except family history. HDV-RNA-positive patients had significantly higher ALT and lower albumin levels when compared to HDV-RNA-negative patients. HDV-RNA-positive patients also had a significantly higher fibrosis stage. In conclusion, these findings demonstrated that HDV infection is endemic and still a serious problem in the Elazig region of eastern Turkey. HDV infection is significantly related to the family exposure and increases the risk of severe liver fibrosis in this region.