1. She said the number of people with flu will increase in the coming weeks.

Question

2. She said the number of people with flu would increase in the coming weeks.
3. She said, "The number of people with flu will increase in the coming weeks."
4. She said the number of people with the flu will increase in the coming weeks.
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Which sentences are grammatical?
Do we have to use 'will' or 'would'?
Can we use both 'flu' and 'the flu'?

Answer 1

All are syntactically correct
"flu" and "the flu" are both commonly used
1,3,4 indicate what she thinks will happen in the future
#2 indicates a past opinion, and might or might not have actually happened.