Can People Be Immortal?

I dont really believe in it...

Perhaps someday we may be able to increase our life spans by working at a cellular level but there are always new diseases that humans aren't immune to. A long time ago, the bubonic plague was the #1 killer of the century (exageration I know) but my point is, who knows what new diseases we would encounter as we live longer...? I mean, if you brought small pox back in time and gave it to cavemen, you could wipe out the Earth.