Step 1 :The function \(N(t)=\frac{13,000}{1+999 e^{-t}}\) models the number of people in a small town who have caught the flu \(t\) weeks after the initial outbreak.
Step 2 :The initial number of people who were ill can be found by substituting \(t=0\) into the function. This is because the function models the number of people who have caught the flu \(t\) weeks after the initial outbreak, so at \(t=0\), this would represent the initial number of people who were ill.
Step 3 :Substituting \(t=0\) into the function gives us \(N(0)=\frac{13,000}{1+999 e^{0}} = 13.0\)
Step 4 :Final Answer: The initial number of people who were ill is \(\boxed{13}\).