Miami (CNN) Fisher Island is about seven minutes by boat from Miami Beach. But the posh enclave is a world away from the rest of South Florida when it comes to coronavirus testing.

After the nearly 800 families in what Bloomberg calls the richest ZIP code in America became concerned about Covid-19, they did not wait in long lines for a test.

Fisher Island has its own health clinic, operated by the University of Miami Health System. The wealthy community is paying for newly available antibody testing for all of its residents -- half of whom are older than 60 -- and its staff, from housekeepers to marina workers. Some 1,250 employees and residents have been tested thus far, according to a spokeswoman for the community.

This amenity contrasts with the rest of South Florida, where no large concentration of residents have been able to take the simple blood test that determines whether they have antibodies that resulted from exposure to the virus.

The blood test is different from the nasal test, which is used to diagnose the illness. The nasal tests have becoming increasingly available in South Florida, but the wait for it can be long.

Testing on the private island, first reported by the Miami Herald , raised eyebrows and some consternation.

I cannot reconcile the shoeless, mask-less, hungry children we fed today with this headline. Everyone on exclusive Fisher Island, even the staff, can get tested for coronavirus. https://t.co/WFYSVF0ymE — Alberto M. Carvalho (@MiamiSup) April 14, 2020

"I cannot reconcile the shoeless, mask-less, hungry children we fed today with this headline," Alberto M. Carvalho, superintendent of Miami-Dade County Public Schools, tweeted earlier this week. "Everyone on exclusive Fisher Island, even the staff, can get tested for coronavirus."

While the optics may suggest elitism, the health system stresses the mass testing on the island, which is just below South Beach and is accessible only by ferry or yacht, is justified.

One of the first confirmed cases of coronavirus in Miami-Dade County was on Fisher Island, they say. According to the state health department , there are between five and nine confirmed cases in the ZIP code.

About 950 residents and family members are on the island now, but that is a seasonal number, according to officials.

The tests are made by BioMedomics, according to Sissy DeMaria, spokesman for Fisher Island. On its website, the company said its blood test has not been reviewed by the Food and Drug Administration but is permitted under emergency guidance issued by the agency.

The University of Miami said the tests were in accordance with its clinical standards.

Still, providing them to all of Fisher Island "may have created the impression that certain communities would receive preferential treatment.

"That was not our intent," said spokeswoman Lisa Worley. She cited the confirmed case, the age of residents and the fact many had returned from travel to the Northeast.

"These factors, at the time, were taken into consideration when the request was received. The health system is revising its process for reviewing testing outreach requests to ensure it meets our mission as we work on the front lines to manage this pandemic for the South Florida community," she said.

Researchers have begun providing countywide blood tests in Miami-Dade. The rollout has been relatively slow; about 700 have been completed and they have been available so far only to those who have chosen to participate in a sampling of residents to determine exposure, a person connected to the testing program told CNN.

Gov. Ron DeSantis last Friday said the state was working to provide wider antibody testing, according to CNN affiliate WFLA.

Instead of looking for traces of the virus, blood tests examine the body's response to the virus: antibodies. The FDA warns they could lead to false negatives because antibodies may not be detectable early in infection.

Still, experts say the antibody tests can be helpful in understanding how widespread coronavirus really is, since they should be able to detect past infections -- even if someone had few or no symptoms.

It's not clear why Fisher Island chose the blood test over the nasal test, which is used to diagnose Covid-19. But results for the former are faster and the community was able to procure a large quantity.

People across the country in recent weeks have had more access to testing, including drive-thru stations.

Miami-area residents have spent hours waiting for them at Hard Rock Stadium, but there was some good news this week: Officials will be able to take throat cultures, a change from nasal swabs, from 750 people per day, up from 400 , according to local reports.

Fisher Island was known for its coconut palms and mangrove concentrations.

The antibody testing on Fisher Island began April 6, according to DeMaria. The tests cost $17 each.

DeMaria told CNN the community "remains vigilant and continues to actively promote social distancing measures, is encouraging the use of face masks, has closed all Club amenities including golf/tennis/marina/restaurant (takeout only) facilities, and has restricted Island access to only essential personnel and visitors, in addition to all other steps recommended by the CDC, the State of Florida and Miami-Dade County Executive Orders."

DeMaria said a resident is giving $200,000 to a charitable foundation providing antibody testing "for hard hit areas in Miami." She says the island philanthropic fund has contributed $100,000 to Feeding South Florida and $50,000 to the United Way for pandemic relief.

There used to be only one doctor on Fisher Island. Even when seriously ill, residents had to take a ferry to Miami for medical attention. The University of Miami Health System clinic was established about two years ago; it provides multiple services for members, including 24/7 access to on-call doctors.

On its website, the 216-acre barrier island portrays a utopia of high-end comfort and camaraderie, with people from more than 40 countries rubbing elbows -- before the pandemic.

The average income among residents was $2.5 million in 2015, according to a Bloomberg analysis of Internal Revenue Service data.

Condominiums, ranging in size from 2,000 to 10,000 square feet, sell for between $2 million and $40 million.