You don't have to answer. I know as well as you do... it's incurable.
9 seconds sound clip from the The Last Man on Earth (1964) movie soundboard.
You can hear this line at 01:10:05 in the Blu-ray version of the movie.
Quote context
[...]
- As a result, I have immunity.
- It's only a guess, but it's all I have to go on.
- You don't think that I'm immune, do you?
- It's a simple matter to find out whether you are or not.
- What will you do if I am infected? Cure me?
- You don't have to answer. I know as well as you do... it's incurable.
- If not of killing the germ, at least of containing it, keeping it from spreading.
- If I had the equipment, the time. Which you don't.
- I was. And without that injection, I'll be one again.
[...]