Rabies - Mad Dog's Menace
- Etiology: Lyssavirus (Rhabdoviridae); bullet-shaped RNA virus.
- Transmission: Animal bite (dogs, bats); bat cave aerosols.
- Pathogenesis: Enters PNS → retrograde axonal transport to CNS. Incubation: 1-3 months (variable).
- Clinical:
- Prodrome: Fever, paresthesia at bite site.
- Furious (~80%): Agitation, hydrophobia, aerophobia.
⭐ Hydrophobia is pathognomonic in furious rabies.
- Paralytic (~20%): Ascending flaccid paralysis.
- Diagnosis:
- Clinical; Negri bodies (intracytoplasmic inclusions: hippocampus, Purkinje cells).
- dFA (skin biopsy), RT-PCR (saliva, CSF).
- Clinical; Negri bodies (intracytoplasmic inclusions: hippocampus, Purkinje cells).
- Post-Exposure Prophylaxis (PEP):
- Wound: Wash (soap & water, 15 mins).
- Rabies Immunoglobulin (RIG): Infiltrate wound, rest IM.
- Human (HRIG): 20 IU/kg.
- Equine (ERIG): 40 IU/kg.
- Vaccine (IM):
- Essen: Days 0, 3, 7, 14, 28.
- Zagreb: Days 0 (2 doses), 7, 21.
- 📌 PEP: Wash, RIG, Vaccinate!
- Pre-Exposure Prophylaxis (PrEP): Days 0, 7, 21/28 (high-risk).
Arboviruses - Mosquito Mayhem Makers
Arthropod-borne viruses (arboviruses) are primarily transmitted by mosquitoes or ticks.
| Feature | Dengue (Flavivirus) | Chikungunya (Alphavirus) | Japanese Encephalitis (JE) (Flavivirus) | Kyasanur Forest Disease (KFD) (Flavivirus) |
|---|---|---|---|---|
| Vector | Aedes aegypti/albopictus | Aedes spp. | Culex tritaeniorhynchus | Haemaphysalis spinigera (tick) |
| Reservoir | Humans (4 serotypes) | Humans | Pigs, Ardeid birds | Monkeys, Rodents |
| Key Notes | Break-bone fever, rash. 📌 Warning signs: abd. pain, persistent vomiting, fluid accumulation, mucosal bleed, lethargy, liver >2cm, ↑Hct + rapid ↓platelets (<100,000/mm³). DHF/DSS. Dx: NS1 Ag, IgM/IgG. | Severe, debilitating arthralgia (may be chronic), fever, rash. Differentiate from Dengue. | Encephalitis, seizures, altered sensorium. CSF pleocytosis. Vaccine preventable. | Biphasic: fever/myalgia → hemorrhagic/neuro sx. South India (Karnataka focus). |
Other Threats - Zoonotic Spillover Surprises
- Influenza (Orthomyxoviridae)
- Antigenic drift (gradual) & shift (sudden, major changes)
⭐ Antigenic shift in Influenza A viruses is responsible for pandemics.
- H5N1 (Avian Flu), H1N1 (Swine Flu) - significant pandemic risk
- Tx: Oseltamivir
- Nipah Virus (Paramyxoviridae, Henipavirus)
- Reservoir: Fruit bats (Pteropus); Pigs are intermediate hosts
- Human-to-human transmission documented
- Causes encephalitis, severe respiratory illness; High Case Fatality Rate (CFR)
- Tx: Ribavirin efficacy doubtful
- Crimean-Congo Hemorrhagic Fever (CCHF) (Nairovirus, Bunyaviridae)
- Vector: Ticks (esp. Hyalomma genus)
- Key: Hemorrhagic symptoms, thrombocytopenia
- Tx: Ribavirin (supportive care crucial)
- Hantavirus (Bunyaviridae)
- Transmission: Inhalation of aerosolized rodent excreta (urine, feces, saliva)
- Causes: Hantavirus Pulmonary Syndrome (HPS) or Hemorrhagic Fever with Renal Syndrome (HFRS)
High‑Yield Points - ⚡ Biggest Takeaways
- Rabies: Transmitted by animal bites; Negri bodies are pathognomonic; post-exposure prophylaxis is crucial.
- Dengue & Chikungunya: Both transmitted by Aedes mosquitoes; Dengue causes hemorrhagic fever & thrombocytopenia, Chikungunya causes severe arthralgia.
- Japanese Encephalitis: Transmitted by Culex mosquitoes; pigs are amplifying hosts; causes childhood encephalitis.
- Kyasanur Forest Disease (KFD): Tick-borne viral hemorrhagic fever; monkeys are reservoirs; endemic to Karnataka.
- Avian Influenza (H5N1/H7N9): High mortality in humans; direct contact with infected birds; antigenic shift poses pandemic risk.
- Crimean-Congo Hemorrhagic Fever (CCHF): Tick-borne (Hyalomma); causes severe hemorrhagic symptoms and high fatality rate.
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