Good question! A helical capsid is basically a long, helical structure that spirals around the viral RNA or DNA. It’s kind of like a spring or a coil. Some examples of viruses with helical capsids are the tobacco mosaic virus (affects plants) and rabies virus. They both have that spiral shape, which helps them pack their genetic material tightly.
In contrast, an icosahedral capsid is a bit more symmetrical. Imagine a soccer ball made up of 20 triangular faces. That’s the icosahedral shape. Viruses like polio and herpes simplex have this type of capsid. The icosahedral structure is super stable, which helps the virus survive longer outside the host.
Hope that helps! Let me know if you need more info!