What are the common infectious diseases specific to Korea and their treatment options?

Common Infectious Diseases Specific to Korea and Their Treatment Options

Chronic hepatitis B (CHB), hepatitis C (HCV), scrub typhus, and hemorrhagic fever with renal syndrome (HFRS) are the most prevalent infectious diseases specific to Korea, with CHB being the most significant public health concern requiring antiviral therapy based on clinical phase assessment.

Chronic Hepatitis B (CHB)

Hepatitis B virus (HBV) infection remains a major public health concern in Korea despite declining prevalence rates due to national vaccination programs.

Epidemiology:

• HBsAg positivity rate: 3.4% for males and 2.6% for females (2012) 1
• Prevalence declined from 8-9% in males and 5-6% in females before the 1980s 1
• National vaccination program initiated in 1995 1
• Most Korean CHB patients are infected with HBV genotype C, which is associated with:
  • Lower HBeAg seroconversion rates
  • More rapid progression to cirrhosis and hepatocellular carcinoma (HCC)
  • Reduced efficacy of interferon treatment
  • Higher rates of relapse after antiviral treatment 1

Clinical Phases and Management:

1. Immune-tolerant phase: HBeAg(+), normal ALT, high viral replication, minimal histological disease
2. Immune-active phase: HBeAg(+), elevated ALT, lower viral replication, active disease
3. Immune-control phase: HBeAg(-), low/undetectable HBV DNA, reduced risk of cirrhosis/HCC
4. Immune-escape phase: HBeAg(-), elevated ALT, moderate to high viral replication
5. HBsAg-clearance phase: HBsAg(-), anti-HBc(+) 1

Treatment Approach:

Treatment decisions should be based on clinical phase, ALT levels, HBV DNA levels, and evidence of liver damage. Antiviral therapy is typically indicated in immune-active and immune-escape phases.

Hepatitis C (HCV)

Epidemiology:

• Overall prevalence: 0.78% in adults ≥20 years (2009) 1
• Higher prevalence in females (0.83%) than males (0.75%) 1
• Increasing prevalence with age (20-29 years: 0.34%, ≥70 years: 2.31%) 1
• Geographic variation: highest in Pusan (1.53%) and Jeollanam-do (2.07%) 1

High-risk populations:

• Intravenous drug users: 48.4-79.2% prevalence 1
• Hemodialysis patients: 5.9-14.7% prevalence 1
• HIV-coinfected individuals: 5.0-6.3% prevalence 1
• Hemophilia patients: 20.0% prevalence 1
• Leprosy patients: 67.7% prevalence 1

Genotype Distribution:

• Genotype 1b: 45-59% of cases
• Genotype 2a: 26-51% of cases 1

Treatment Approach:

Treatment should be tailored based on HCV genotype, with direct-acting antivirals being the standard of care.

Scrub Typhus

Epidemiology:

• Caused by Orientia tsutsugamushi 2
• Seasonal pattern: predominantly in autumn 3
• Challenging to diagnose due to more than twenty serotypes and similar clinical symptoms with other acute febrile illnesses 2

Diagnosis:

• Rapid diagnostic tests (RDTs) show high sensitivity (98.6% for IgM and 97.1% for IgG) and specificity (98.2% for IgM and 97.7% for IgG) 2
• ImmuneMed RDT demonstrates superior performance compared to other diagnostic methods 2

Treatment:

• Streptomycin is indicated for treatment of susceptible strains of microorganisms causing tularemia and other non-tuberculosis infections 4
• Doxycycline is typically the first-line treatment for scrub typhus

Hemorrhagic Fever with Renal Syndrome (HFRS)

Epidemiology:

• Caused by Hantaan and related viruses 5
• Average prevalence rate: 0.81 per 100,000 population (2001-2010) 6
• Case fatality rate: 1.01% 6
• Demographics:
  • More common in men (57%) than women (43%)
  • Higher prevalence in patients older than 40 years (82.1%)
  • Highest among farmers (35.6%) 6

Seasonal and Geographic Distribution:

• Seasonal pattern: 71.3% of cases occur in the last quarter (October to December) 6
• Geographic distribution: more common in western Korea (68.9%) than eastern Korea (31.1%) 6
• Significantly higher incidence in rural areas (80.3%) than urban areas (19.7%) 6

Diagnosis and Treatment:

• Serologic diagnosis based on demonstration of IgM antibodies to Hantaviruses 5
• Treatment is primarily supportive with careful fluid management and dialysis if needed

Other Notable Infectious Diseases in Korea

• Malaria: Prevalent in summer months, with incidence correlated with temperature, humidity, and precipitation 3
• Vibrio vulnificus sepsis: Occurs predominantly in summer, with incidence correlated with meteorological factors 3
• Leptospirosis: Prevalent in autumn, with incidence positively correlated with temperature and humidity in February 3

Climate Change Impact

Climate change appears to be influencing the incidence of infectious diseases in Korea:

• Scrub typhus incidence in endemic regions correlates with temperature and humidity during summer 3
• HFRS incidence correlates with precipitation in November 3
• Leptospirosis correlates with temperature and humidity in February 3
• V. vulnificus sepsis correlates with precipitation in April/May/July 3

Surveillance System

Korea has established a National Notifiable Disease Surveillance System, but timeliness varies by disease:

• Diseases with 1-day reporting requirements show lower compliance (60-70%) compared to those with 7-day requirements (>80%) 7
• Median time from disease onset to notification ranges from 6 to 20 days 7
• The main delay occurs between disease onset and diagnosis, highlighting the need for improved public education and clinical guidelines 7