Why in the news?

  • The declining immunity against Japanese Encephalitis is leading to increased threat of Dengue fever.

Japanese Encephalitis

  • What is it?:
    • It is a vector-borne viral disease caused by the Japanese Encephalitis Virus (JEV).
    • First identified in Japan in 1935, now endemic across 24 countries in the WHO South-East Asia and Western Pacific regions.
    • Major cause of viral encephalitis in Asia.
  • Cause and Transmission:
    • Virus: Flavivirus (same family as Dengue, Zika, Yellow Fever).
    • Transmission Vector: Culex mosquitoes, especially Culex tritaeniorhynchus.
    • Reservoirs: Pigs & water birds (amplifying hosts).
    • Humans: “Dead-end hosts” (cannot spread infection further).
  • Symptoms:
    • Most infections are asymptomatic.
    • Severe cases: High fever, headache, seizures, disorientation, coma.
    • Case fatality: 20–30%.
    • Neurological sequelae: 30–50% survivors develop long-term disabilities (paralysis, cognitive impairment).
  • In India:
    • Endemic in Assam, Bihar, Uttar Pradesh, Tamil Nadu, Karnataka, West Bengal, Odisha.
    • Major outbreaks: Uttar Pradesh & Bihar (notably Gorakhpur region).
    • Outbreaks common in monsoon & post-monsoon periods due to waterlogging.
  • Control Measures by GoI:
    • National Vector Borne Disease Control Programme (NVBDCP) – umbrella programme for JE along with malaria, dengue, etc.
    • Intensified JE–AES Control Programme (2014):
      • Vector control (fogging, larvicides, source reduction).
      • Vaccination drives.
      • Early case detection & referral.
      • Safe drinking water & sanitation.
    • JE Vaccination:
      • SA 14-14-2 (Live Attenuated Vaccine) used widely.
      • It has been integrated into the Universal Immunisation Programme (UIP) since 2006.
      • Focus on children (1–15 years age group).
    • AES-Je management centres in endemic districts for treatment & rehabilitation.

Dengue

  • What is it?:
    • It is a mosquito-borne viral disease caused by the Dengue Virus (DENV), belonging to the Flavivirus genus.
    • First identified in the 18th century; now one of the most prevalent vector-borne diseases globally.
    • WHO classifies dengue as a neglected tropical disease of major global concern.
  • Cause and Transmission:
    • Virus: Four serotypes (DENV-1, DENV-2, DENV-3, DENV-4).
    • Transmission Vector: Female Aedes aegypti (primary) and Aedes albopictus.
    • Transmission cycle: Human–mosquito–human (unlike Japanese Encephalitis, which involves animal reservoirs).
    • High-risk period: Post-monsoon due to water stagnation.
  • Symptoms:
    • Classical Dengue Fever: Sudden high fever, severe headache, retro-orbital pain, muscle and joint pain (“breakbone fever”), rash.
    • Severe Dengue (Dengue Hemorrhagic Fever / Dengue Shock Syndrome): plasma leakage, severe bleeding, organ impairment, shock.
    • Mortality: Less than 1% with proper treatment but up to 20% without.
  • In India:
    • Endemic across most states, especially Delhi, UP, Tamil Nadu, Kerala, Maharashtra, West Bengal.
    • Recurrent outbreaks during monsoon & post-monsoon.
  • Treatment:
    • No specific antiviral treatment.
    • Supportive therapy: fluid replacement, monitoring for shock, paracetamol (avoid NSAIDs like aspirin).
    • Vaccine: Dengvaxia (first licensed dengue vaccine, Sanofi, 2015) – limited use; WHO recommends only for seropositive individuals.
      • Indian trials ongoing for indigenous vaccines.
  • Control Measures by GoI:
    • National Vector Borne Disease Control Programme (NVBDCP): umbrella programme for dengue, malaria, JE, etc.
    • Integrated Disease Surveillance Programme (IDSP): tracks outbreaks and spread.
    • National Dengue Day (May 16) – awareness campaign.
    • Public Health Measures:
      • Source reduction (anti-larval measures, eliminating stagnant water).
      • Fogging and spraying during outbreaks.
      • Community participation through “Dry Day” initiatives.