i need help understanding this question? can some one tell me what exactly i have to do in it

Question

7. Suppose a student carrying a flu virus returns to an isolated
college campus of 1000 students. Determine a differential
equation for the number of people x(t) who have
contracted the flu if the rate at which the disease spreads
is proportional to the number of interactions between the
number of students who have the flu and the number of
students who have not yet been exposed to it.

Answer 1

If w is proportional to u and v, then w = kuv. So, we are told that

dx/dt = kx(1000-x)

I have set it up so that

"the rate at which the disease spreads is proportional to the number of students who have the flu and the number of
students who do not yet have it.

I have no way of estimating how many have been exposed to it, or determining the students' interactions. A poorly worded question. Maybe you have further insight.