A 71 year old female presents with a vesicular rash that burns and itches. Shingles is diagnosed. An oral antiviral:
1. Should be started within 72 hours of onset of symptoms.
2. Must be started within 96 hours of the onset of the rash.
3. Can be started at any time after appearance of the rash.
4. Will nearly eliminate the risk of postherpetic neuralgia?