That's a good point. Disease control services are reasonably justified for the federal entities indicated under the Constitution's Clause 17 of Section 8 of Article I as an example, imo, entities under the exclusive legislative control of Congress, especially for the reason that you indicated.
It remains that the states have never amended the Constitution to grant Congress the specific power to regulate, tax and spend for such services for intrastate-related issues. Therefore any federal government action against ebola concerning intrastate issues is an unconstitutional expansion of federal government powers. This is evidenced by the following excerpts from Supreme Case opinions which not only reflect on this issue, but also show that activist justices are wrong about the constitutionality of unconstitutional federal Obamacare Democratcare.
”State inspection laws, health laws, and laws for regulating the internal commerce of a State, and those which respect turnpike roads, ferries, &c. are not within the power granted to Congress. [emphases added]” —Gibbons v. Ogden, 1824.
“Congress is not empowered to tax for those purposes which are within the exclusive province of the States.” —Justice John Marshall, Gibbons v. Ogden, 1824.
“Inspection laws, quarantine laws, health laws of every description [emphasis added], as well as laws for regulating the internal commerce of a state and those which respect turnpike roads, ferries, &c., are component parts of this mass.” —Justice Barbour, New York v. Miln., 1837.
“Direct control of medical practice in the states is obviously [emphasis added] beyond the power of Congress.” –Linder v. United States, 1925.
So I think that the states need to consider amending the Constitution to grant the feds the power to prevent the spread of disease.
No. The Feds should prevent the entry of disease, not the spread within the US (if that's what you mean). Remember: with an incurable infectious pathogen, the only means is containment. That means borders, and the smaller the area the better. Hence, I think the best model is "county health department" as regulated by the States. So in a sense, this is analogous to the old 'good fences make good neighbors' aphorism.