Health officials didn't confirm news reports that Zika is transmitting in Miami Beach, but said they are probing 8 areas outside the known hot spot.
Another study pinpoints placental cells that Zika can infect, and a report from Brazil describes 2 cases linked to platelet transfusion.
No illnesses have been detected in the woman's coworkers who traveled with her to Miami or in her household contacts.
In another key development, HHS recently declared a public health emergency for Zika virus in Puerto Rico.
Cases in Puerto Rico topped 10,000, as more countries and regions reported local spread, microcephaly, and GBS.
HHS Secretary Burwell says lack of congressional action forced $81 million to be taken from other programs.
The first local case involved a 23-year-old pregnant women, and several other patients infected locally have work ties to the Wynwood neighborhood.
An expert from the March of Dimes said arthrogryposis appears to be a "downstream effect" and shows how severe viral damage can be.
Like another recent microcephaly case in Texas, the baby's mother likely contracted Zika in Latin America during pregnancy.
Sampling and other activities are under way in Palm Beach County, where the newest case was reported, but the patient had traveled to Miami-Dade County.
