RNA Viruses: Paramyxoviruses

Paramyxoviruses - General Properties & Fusion Fanatics

• Structure: Enveloped viruses; helical nucleocapsid. Genome: linear, non-segmented, negative-sense RNA ($-ssRNA$).
  • Key Proteins:
    • F (Fusion) protein: Mediates viral entry and cell-to-cell fusion, forming characteristic syncytia (multinucleated giant cells).
    • HN/H/G protein: Attachment glycoproteins (Hemagglutinin-Neuraminidase, Hemagglutinin, or Glycoprotein).
• Replication: Occurs in the cytoplasm.

  ⭐ Paramyxoviruses possess an RNA-dependent RNA polymerase in their virion, essential for transcription of $-ssRNA$ to $+mRNA$.

• Pathogenesis: Syncytia formation is a hallmark, driven by F protein.
• 📌 Mnemonic: PaRaMyxo = Parainfluenza, RSV, Measles, Mumps.

Measles (Rubeola) - Koplik's Calling Card

• Virus: Morbillivirus (Paramyxoviridae), highly contagious RNA virus.
• Prodrome: Fever with Cough, Coryza, Conjunctivitis (the 3 Cs), lasting 3-4 days.
  • Koplik's spots: Pathognomonic bluish-white lesions on buccal mucosa opposite molars.

  ⭐ Koplik's spots on the buccal mucosa are pathognomonic for measles and appear 1-2 days before the rash.

• Rash: Erythematous maculopapular rash; begins on face/hairline, spreads cephalocaudally over 3 days.
• Complications: 📌 "MEASLES gives you POME"
  • Pneumonia (most common cause of death)
  • Otitis Media
  • Myocarditis
  • Encephalitis (ADEM), Subacute Sclerosing Panencephalitis (SSPE - rare, late, fatal).
• Diagnosis: Primarily clinical; confirmed by IgM antibodies or PCR.
• Prevention: MMR vaccine (live-attenuated virus).

Mumps Virus - Swollen & Sore Saga

• Genus: Rubulavirus; single-stranded RNA virus.
• Primary Manifestation: Acute parotitis (painful, unilateral or bilateral swelling of salivary glands).
  • 📌 Mumps makes your Parotids and Privates Puffy.
• Systemic Complications:
  • Orchitis: Inflammation of testes, common in post-pubertal males, can lead to ↓fertility or rarely sterility.
  • Meningitis: Aseptic meningitis is a frequent neurological complication.
  • Encephalitis: Less common but serious.
  • Pancreatitis: Abdominal pain, nausea.
  • Oophoritis: Inflammation of ovaries.
• Diagnosis: Primarily clinical; confirmed by detecting IgM antibodies or viral RNA via PCR.
• Prevention: Highly effective MMR (Measles, Mumps, Rubella) live-attenuated vaccine.

  ⭐ Mumps is a common cause of aseptic meningitis.

Respiratory Syncytial Virus (RSV) - Tiny Airways Terror

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Parainfluenza Viruses (PIVs) - Croup's Croaky Crew

• Types & Genera:
  • Respirovirus: HPIV-1, HPIV-3
  • Rubulavirus: HPIV-2, HPIV-4
• Clinical Features:
  • Croup (Laryngotracheobronchitis): Barking cough, inspiratory stridor, hoarseness (esp. HPIV-1, HPIV-2). 📌 Croup: Steeple sign on neck X-ray.
  • Bronchiolitis, pneumonia (esp. HPIV-3).
• Diagnosis: Clinical grounds; confirmed by Immunofluorescence (IF), PCR.
• Management: Supportive; no specific antiviral or vaccine available.

⭐ Parainfluenza viruses, particularly types 1 and 2, are the most common cause of croup (acute laryngotracheobronchitis) in children. oka

High‑Yield Points - ⚡ Biggest Takeaways

• Enveloped, single-stranded, negative-sense RNA viruses; replicate in the cytoplasm.
• Characteristic syncytia formation (multinucleated giant cells) due to F (fusion) protein.
• Measles (Rubeola): Koplik's spots, maculopapular rash (cephalo-caudal spread), risk of SSPE.
• Mumps: Parotitis, orchitis/oophoritis, aseptic meningitis.
• RSV (Respiratory Syncytial Virus): Most common cause of bronchiolitis and pneumonia in infants (<1 year).
• Parainfluenza viruses: Major cause of croup (laryngotracheobronchitis).