It is odd. the first doesn't work for me. The second two are just OK.
It is more common to say "with smallpox".
Interested in Language
1. There were people having smallpox.
2. The people having smallpox were treated with cidofovir.
3. Some people having smallpox suffered from complications.
Is 'people having smallpox' grammatical?
Is it OK to say 'there were people having a picnic in the park'?