Why would you come to a forum and not just check the rulebook? Page 13 under outbreaks answers your question.
Have you had nails for breakfast? Man, it's just a question!
Anyway, the actual Outbreak text didn't answer the question. After reading your comment, I went and rechecked the rules and found that the little white box does answer this question (I didn't read these bits to the group when I played as we were focused on the actual rules).
So, thanks for that but I don't see why you have to be so rude and aggressive about it.
You could have just said "FYI, there's a scenario for this in the rule book on P13 in the white box".
Same outcome but a completely different message.
Oh, and thank you to the other two posters for your help also.
Good day sirs/madams.