underwent particular disease?

How shall I say about someone who was ill in the past.

Can I say that he/she underwent particular disease?

Not really. The usual word is “contracted”, but it would be good to see the whole sentence. (struck out my non-great reply; see later thread)

Respondents who have had and/or treated of cold and flu in their children in the last 1.5 month

I’d like to point out that respondents suffered from disease instead of having had it.

Sorry, I don’t understand the distinction. Suffering from a disease is the same as “having” it. Can you explain the distinction in another way?

“Have” is a simple way to say that one had disease. but I’d like to put emphasis on having been ill and finaly recovered from disease. This process I would name “underwent disease”, however, It’s pointed out that the word “undergo” can’t be used in this context. can you provide any other synonyms for having had disease?

If you want to exclude people who have not yet recovered (or, I suppose, in the worst case, who died), I think it’s clearer to say so explicitly. You can say:

“Respondents with a child who has had a cold or flu in the last six weeks but has now recovered.”

“1.5 months” is a bit clunky, and if you can say “six weeks” then that sounds better. The “in their children” phrasing is not right.

(By the way, my original answer in this thread was not great, because “contracted” really means “caught” more than “had” or “suffered from”.)

If I say: Respondents who have had cold and flu and/or treated their child’s cold and flu in the last 6 weeks, will it sound correct?

It critical to say that respondens had cold and flu and treated their child’s cold and flu.

This is correct English:

“respondents who, in the last 6 weeks, have had a cold or flu and/or treated their child’s cold or flu”

(“cold” and “flu” are considered different things, and you do not normally have both together. I moved “in the last 6 weeks” because in the previous position it did not unambiguously apply to both cases, which I assume is what you want.)

Although that is correct English, it means something different from what I previously thought you wanted to say. Also, it is not very clear why you are making a distinction between the respondent having the disease and the child being treated for the disease, and this may raise doubts or questions in the mind of the reader.

OK. Dozy, thank you very much. You are helping me to build correct English!