This episode explores the paramyxoviruses, enveloped negative-sense single-stranded RNA viruses known for their ability to induce cell fusion. Drawing from Murray’s Chapter 48, it examines how viral surface proteins drive respiratory infection and characteristic cytopathic changes.

The family includes:

* Respiratory syncytial virus (RSV)

* Parainfluenza viruses

* Measles virus

* Mumps virus

The defining mechanistic feature is the fusion (F) protein, which allows viral envelopes to merge with host cell membranes and, importantly, promotes the formation of syncytia - multinucleated giant cells created by fusion of infected cells.

Clinically:

* RSV is a major cause of bronchiolitis in infants

* Parainfluenza viruses cause croup

* Measles produces systemic infection with rash and immunosuppression

* Mumps can affect salivary glands, testes, and central nervous system

Conceptually, paramyxoviruses illustrate how membrane fusion facilitates direct cell-to-cell spread, bypassing extracellular immune defences. Vaccination plays a critical preventive role in measles and mumps.

Key Takeaways

* Paramyxoviruses are enveloped negative-sense RNA viruses

* Fusion protein enables syncytium formation

* Primarily infect respiratory epithelium

* Some cause systemic disease with rash or glandular involvement

* Vaccination significantly reduces disease burden

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