PARAMYXOVIRUS – MEASLES

Definition

• Measles virus is a highly contagious RNA virus from the family Paramyxoviridae.
• It is zoonotic and spreads between animals and humans.

Morphology

• Single-stranded, negative-sense RNA virus.
• Helical nucleocapsid with a lipid envelope.
• Size 150–200 nm.
• Envelope contains H (hemagglutinin) glycoprotein for attachment and fusion.
• Nucleocapsid contains RNA + nucleoprotein (N).
• Peplomers present on the envelope.

Types

• Measles virus type A (MV-A)
• Measles virus type B (MV-B)

Pathogenesis

• Entry through respiratory droplets.
• Virus binds to CD46 receptor.
• Enters host cell by receptor-mediated endocytosis.
• Viral RNA released into cytoplasm.
• Replication and protein synthesis occur.
• New virions assemble and bud out of the cell.
• Virus spreads causing fever, cough, cold, and rash.

Additional Morbillivirus steps:

• Entry
• Fusion
• Release of RNA
• Synthesis and assembly

Memory trick: E-F-R-S

Clinical Features

• Fever, cough, cold, conjunctivitis.
• Koplik spots.
• Maculopapular rash (3–5 days after symptoms).
• Rash lasts 5–7 days.
• Otitis media and pneumonia may occur.

Complications

• Encephalitis
• Laryngotracheobronchitis
• Otitis media
• Pneumonia
• Diarrhea
• Malnutrition and dehydration

Laboratory Diagnosis

• Detection of measles antigen in respiratory samples.
• PCR for viral RNA.
• ELISA for IgM antibodies.
• Virus isolation from throat/nasal swabs.
• RT-PCR for RNA confirmation.

Memory trick: V-S-R-P-R V – Virus isolation S – Serology R – PCR P – RT-PCR R – RNA detection

Management

• Supportive care: hydration, nutrition.
• Antibiotics for secondary infections.
• Antivirals in severe cases.
• Vaccination is the best prevention.

Memory Trick

MEASLES M – Multiply in the body E – Enter through droplets A – Adhere to CD46 S – Spread to cells L – Lead to symptoms E – Encephalitis risk S – Spread by droplets