[Retric]

Local governments in disaster prone areas tend to have significant emergency funds they can tap into. Doing so now to do an inventory of supplies, run some disaster planning, and possibly fill in any gaps is completely reasonable.

They are unusually likely to see a small scale outbreak and effective early responses could make a huge difference.

[AstralStorm]

Most importantly this allows using the emergency funds to boost local healthcare in case of an epidemic. Without the declaration the local government is unable to do so, just use it to bolster standard plans.