Arboviruses: Overview - Buzzing Bad News
- Arboviruses: Arthropod-borne viruses, transmitted by blood-sucking arthropods after biological replication within them.
- Transmission Cycle: Virus replicates in both arthropod vector & vertebrate host.
- Humans are often incidental or dead-end hosts.
- Key Vectors:
- Mosquitoes: Aedes (e.g., Dengue, Chikungunya, Zika), Culex (e.g., Japanese Encephalitis, West Nile Virus), Anopheles.
- Ticks: e.g., Ixodes (Kyasanur Forest Disease), Dermacentor.
- Nature: Predominantly RNA viruses (e.g., Flavivirus, Alphavirus, Bunyavirus); mostly enveloped.
⭐ Most arboviruses belong to families: Togaviridae (Alphavirus), Flaviviridae (Flavivirus), Bunyavirales order (e.g., Nairoviridae, Peribunyaviridae), and Reoviridae (Orbivirus).
Arboviruses: Classification - Viral Family Album
Arboviruses (arthropod-borne viruses) are classified into four main viral families/orders:
| Family | Genus | Key Arboviruses (Indian Context) |
|---|---|---|
| Togaviridae | Alphavirus | Chikungunya (CHIKV), Sindbis (SINV) |
| Flaviviridae | Flavivirus | Dengue (DENV), JE, WNV, KFDV |
| Nairoviridae (Bunyavirales) | Nairovirus | CCHF virus, Ganjam virus |
| Phenuiviridae (Bunyavirales) | Phlebovirus | Sandfly Fever virus (e.g., SFSV) |
| Peribunyaviridae (Bunyavirales) | Orthobunyavirus | Batai virus |
| Reoviridae | Orbivirus | Bluetongue Virus (BTV - vet), Palyam virus |
Arboviruses: Clinical Syndromes - Symptom Showdown
Arboviruses manifest in distinct clinical syndromes, crucial for differential diagnosis.
| Syndrome | Key Viruses (Vectors) | Core Features | Key Differentiators |
|---|---|---|---|
| Encephalitis | JE (Culex), WNV (Culex), Chandipura (Sandfly) | Altered sensorium, seizures, focal deficits. WNV: flaccid paralysis. Chandipura: rapid, children <15y. | JE: parkinsonian. |
| Hemorrhagic Fevers | Dengue (Aedes), KFD (Ticks) | Fever, hemorrhage, shock. KFD: biphasic, neuro. | Dengue: ↑HCT, ↓platelets. KFD: "Monkey disease", forest. |
| Fever-Arthralgia-Rash | Chikungunya (Aedes), Zika (Aedes) | High fever, severe arthralgia, rash. Zika: conjunctivitis. | CHIKV: "Bending up" pain. Zika: GBS, congenital syndrome. |
⭐ Dengue warning signs are critical for early detection of severe dengue: abdominal pain/tenderness, persistent vomiting, clinical fluid accumulation (e.g., ascites, pleural effusion), mucosal bleeding, lethargy/restlessness, liver enlargement >2 cm, and laboratory finding of ↑hematocrit concurrent with rapid ↓platelet count.
Arboviruses: Dx & Prevention - Detect & Deflect
Diagnosis (Detect):
- Primary: RT-PCR (blood, CSF, urine) during viremic phase (first week). Sensitive/specific.
- Serology: IgM capture ELISA (MAC-ELISA) from day 5-7 (CSF/serum). Paired sera for IgG rise.
- Virus Isolation: Cell culture; less for routine Dx.
Prevention & Control (Deflect):
- Vector Control: Key!
- Mosquitoes: Source reduction (stagnant water), larvicides (Temephos), adulticides (fogging), personal protection (DEET, nets). 📌 "DENY, DESTROY, DEFEND."
- Ticks: Avoid areas, protective clothes, repellents (Permethrin).
- Vaccination:
- JE: Live (SA 14-14-2), inactivated.
- KFD: Formalin-inactivated.
- Yellow Fever: Live (17D strain).
- Surveillance & Education.
⭐ JE vaccine (live attenuated SA 14-14-2 strain) single dose can provide long-term, possibly lifelong, immunity.
High‑Yield Points - ⚡ Biggest Takeaways
- Arboviruses: Arthropod-Borne Viruses, transmitted by mosquitoes (Aedes, Culex) and ticks.
- Key families: Togaviridae (Chikungunya), Flaviviridae (Dengue, JE, Zika, KFD), Bunyaviridae (CCHF).
- Dengue: 4 serotypes; secondary infection with different serotype risks DHF/DSS.
- Japanese Encephalitis (JE): Viral encephalitis in Asia; pigs & birds are amplifying hosts.
- Chikungunya: Characterized by high fever and severe, debilitating arthralgia.
- KFD (Monkey Fever) is a tick-borne hemorrhagic fever in India; Zika causes microcephaly.
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