What are the risk factors for developing hepatitis?

Risk Factors for Hepatitis

Intravenous drug use is the single most important risk factor for hepatitis C (accounting for 80% of cases and approximately 60% of new infections), while for hepatitis B, the primary routes are perinatal transmission in endemic areas and sexual/percutaneous exposure in developed countries. 1

Hepatitis C Risk Factors

High-Risk Exposures

• Injection drug use: Represents 80% of confirmed HCV cases with available risk factor data, with 50-100% of intravenous drug users testing anti-HCV positive 1
• Blood products and transfusions: Account for 10.8% of confirmed cases, though transmission has been virtually eliminated in developed countries (risk <1 in 200,000 in England) 1
• Intranasal cocaine use: Identified as a significant risk factor in 68% of HCV-positive blood donors, likely through sharing contaminated straws 2

Moderate-Risk Exposures

• Hemodialysis: Documented as a parenteral transmission route 1
• Tattooing and body piercing: Particularly ear piercing in men showed statistical significance as a risk factor 2
• Sharing personal items: Razors and toothbrushes can transmit HCV through unapparent parenteral exposure 1, 3
• Occupational needlestick injuries: Estimated transmission risk of 1.8%, though healthcare workers show no higher prevalence than general population 1

Sexual Transmission (Limited Role)

• Sexual transmission risk is low (<5% in long-term monogamous relationships) unless multiple risk factors present 1
• Multiple sexual partners, sexually transmitted disease clinic attendance, and prostitution are associated with increased HCV risk 1
• HIV coinfection facilitates sexual transmission (11.7% seropositivity in HIV-positive homosexuals without transfusion/IVDU history) 1
• No patient in referral studies reported sexual activity as sole risk factor 4

Vertical Transmission

• Risk <6% unless mother is HIV-positive or has high-level viremia 1
• Breastfeeding has not been implicated in HCV transmission 1

Hepatitis B Risk Factors

Perinatal and Early Childhood

• Perinatal transmission from HBeAg-positive mothers: 90% risk of chronic infection in newborns 1
• Infection in children under 5 years: 25-30% develop chronic infection 1
• Close person-to-person contact in hyperendemic areas through open cuts and sores, especially among children 1

Percutaneous Exposures

• Injection drug use: Major risk factor in developed countries 1
• Blood transfusions: Historical risk factor, now largely eliminated through screening 1
• Hemodialysis, organ transplantation: Documented transmission routes 1
• Tattooing and non-sterilized needles: Particularly in traditional practices and large-scale immunization programs in certain countries 1

Sexual Transmission

• Heterosexual contact: Most common method of adult HBV transmission in developed countries (because this exposure occurs most frequently) 1
• Men who have sex with men: Significant risk factor requiring screening 1
• Multiple sexual partners: Associated with increased transmission risk 1

Geographic and Demographic Factors

• Birth in hyperendemic areas: Asia, South Pacific, sub-Saharan Africa, Arctic regions, parts of South America and Middle East 1
• Immigrants from endemic areas: Higher prevalence in developed countries 1
• Age demographics: Most HCV cases occur in 25-34 year age group (38%) and 35-44 year age group (27%), with males affected twice as frequently as females 1

Additional Risk Factors

Immunosuppression-Related

• Immunosuppressive therapy or chemotherapy: Increases risk of HBV reactivation, with high-risk regimens (≥10% reactivation rate) including rituximab-based therapy for lymphoma 1
• HIV coinfection: Associated with higher HBV DNA levels, lower spontaneous HBeAg seroconversion rates, and more severe liver disease 1
• Solid organ transplantation: Increases reactivation risk 1

Coinfections

• HBV/HCV coinfection: More rapid progression of liver disease and higher HCC risk than HBV alone 1
• HBV/HDV coinfection: Higher proportion develop cirrhosis, hepatic decompensation, and HCC compared to HBV alone 1

Occupational and Healthcare-Related

• Healthcare workers treating bleeding injuries: At particular risk, especially in settings without trained providers 1
• Coaches and athletes performing first aid: May have higher risk due to limited knowledge and skills 1

Behavioral and Social Factors

• Incarceration history: Significantly associated with HCV infection 3
• Sex for money or drugs: Risk factor for both HCV and HIV coinfection 3
• Sharing drug paraphernalia: Beyond needles, includes all equipment used in drug preparation 1
• Travel to endemic regions: Increases HBV exposure risk, particularly for professional athletes 1

Important Clinical Caveats

Multiple risk factors are the norm, not the exception: 95.3% of HCV patients in referral practices had identifiable risk factors, with 53.4% having more than two risk factors 4. This has important implications for surveillance using hierarchical algorithms that may miss the complexity of transmission patterns.

Age-related patterns differ: Blood product exposure is less common in younger than older HCV patients, while street drug exposure is more common in younger populations 4.

Environmental persistence: HBV can survive outside the body for prolonged periods, and HBeAg-positive carriers can shed large quantities of viral particles on environmental surfaces through open cuts or sores 1.