“…Further, by Lemma 1, Ω 2 is a compact, absorbing subset of R 5 + , and the largest compact invariant set in {(S, E, I, R,W ) ∈ Ω 2 :V 1 = 0} is {Q}. Therefore, by the Lasalle's invariance principle (see, for instance, [15,Theorem 3.1] and [7,8,9,10,11,12,13,14] for other applications), every solution of system (1) with initial conditions in R 5 + converges toQ as t → +∞.…”