there are imported cases, but now they will monitor for locally acquired cases.
locally acquired cases mean that the local mosquitoes are spreading the virus (a major problem that will require vector control e.g. spraying pesticides, destroying areas of stagnant water, and protecting people from mosquitoes e.g. insect repellents, screens, clothing that covers you up)
Certain clinics are chosen to report on such things (I worked in clinics where this was done for flu). Expect false positives because this is done empirically (based on symptoms and where you traveled etc) unless the lab work confirms, because the lab takes forever.
I'll give an example: the high RMSF reports in Oklahoma was probably because the IHS rural clinics diagnosed all patients with fevers and with a history of tick bits were treated with antibiotics before the lab came back. A large number of reported cases was from one of the designated reporting clinics, who reported all suspicious cases as RockyMountain Spotted Fever, even though several other viruses (e.g. influenza, Lyme disease, Colorado tick fever, Erlicheosis, and more recently, West Nile Virus) had similar symptoms...but you simply didn't wait for the rash to treat (by the time you got the rash, which appears after a few days, often you were quite ill) and the lab took two weeks to confirm you had a case...
Many locals had high RMSF titers from previous, usually untreated, mild infections. So the only way to confirm a case was to do a second test in two weeks and see if the antibody count went up.
Indeed, few patients come back for the "two week later" test that will actually confirm you had it.
Since Zika is a new virus, and they now have more sensitive tests to diagnose it, the accuracy of monitoring the infection will be a lot easier.
The CDC also will be checking for the mosquito Aedes now (up to now, they mainly checked for a different mosquito that carried West Nile Virus).
The CDC also is planning to screen blood donations in affected areas. LINK
Despite the absence of local mosquito-borne transmission or Zika virus–infected mosquitoes currently, expanded source control and applied larvicides and adulticides for Aedes mosquitoes might reduce the likelihood for local transmission. Similar approaches could be considered in other jurisdictions that are likely to have large numbers of imported human cases of Zika virus disease and potential Zika vectors.
Zika is actually a mild disease: but like Rubella, it affects the unborn babies in pregnant women...but unlike Rubella, which mainly caused problems in early pregnancy, this virus affects babies later in pregnancy.
and no, I don't have expertise in Zika: We didn't have it in our area of Africa.