Herpesviruses, Arboviruses: Dengue & Chikungunya Explained

Herpesviruses are DNA viruses that infect once and hide in nerve cells for life (latency). Key members: HSV-1 (cold sores), HSV-2 (genital herpes) and VZV (chickenpox, later shingles). Arboviruses spread by arthropod bites; India's most important are dengue virus and chikungunya virus, both carried by Aedes mosquitoes.

Nearly every adult carries a herpesvirus, dengue outbreaks strike every monsoon, and chikungunya leaves joint pain lasting months. Telling a herpes blister from an allergy, or dengue from ordinary viral fever, is daily clinical work.

Key Concepts

• Latency: viral DNA rests silently in nerve ganglia; stress or illness can reactivate it, causing blisters along the same nerve path.
• Tzanck smear: herpesviruses fuse cells into multinucleated giant cells visible on a smear from a blister base.
• NS1 antigen: dengue protein detectable in blood during the first 5 days of fever, before antibodies appear.
• Four dengue serotypes (DEN-1 to 4): infection protects only against that serotype; a second infection with another serotype risks severe dengue.
• Warning signs: severe abdominal pain, persistent vomiting, bleeding, lethargy and rising hematocrit with falling platelets signal severe dengue.

How It Works

Herpesvirus infects skin, causes blisters, then travels up nerves to ganglia where it sleeps for life until reactivated. Dengue arrives via a daytime-biting Aedes aegypti mosquito breeding in clean stagnant water. The virus multiplies in immune cells causing high fever and body ache. In second infections, leftover antibodies can help the new serotype enter cells more easily, causing plasma leakage and shock. Chikungunya, also Aedes-spread, causes sudden fever with intense joint pain lasting months but rarely the dangerous leakage of severe dengue.

Worked Example

A district reports 480 confirmed dengue cases and 12 deaths. The case fatality rate is:

1. Deaths = 12; cases = 480
2. CFR = (12 ÷ 480) × 100 = 0.025 × 100 = 2.5%

A 2.5% CFR signals moderate severity: hospitals must watch warning signs and manage fluids carefully, since delayed recognition of shock causes most dengue deaths.

Common Misconceptions

• "Every dengue patient needs platelet transfusion." Only for severe bleeding or critical counts. Careful IV fluid management during the critical phase is the real lifesaver.
• "Shingles needs antibiotics." It is viral; early acyclovir is the correct drug.
• "One dengue infection protects forever." Only against that serotype; the second infection is the dangerous one.

Real-World Applications

• Acyclovir: shortens herpes/shingles episodes; lifesaving in encephalitis and neonatal herpes.
• Dengue testing: NS1 in the first 5 days, then IgM/IgG, confirms diagnosis and distinguishes primary from secondary infection.
• Vector control: removing stagnant water and larviciding stops both dengue and chikungunya at the source.
• Supportive care: paracetamol (never aspirin/NSAIDs in dengue, due to bleeding risk), hydration and monitoring of hematocrit and platelets.

Herpesviruses hide in nerves for life and reactivate as cold sores or shingles, treated with acyclovir; dengue and chikungunya arrive by daytime mosquito bites, with dengue's second infection carrying the real danger. Early NS1 testing, warning-sign watch, careful fluids and mosquito control save lives every monsoon.