As of Sept. 27, 25 cases of Zika had been confirmed in the territory, including multiple pregnant women, according to Dr. Ronald Georges, the government’s medical officer of health.

There are probably many other cases as well: More tests are still pending, and research suggests that only 20 percent of sufferers exhibit symptoms, Dr. Georges said.

The mosquito-borne virus, which can cause serious birth defects, was first confirmed here in late August. Since then, a growing number of residents experiencing Zika-like symptoms have sought to get tested. But that process takes time, in part because Zika tests are not available locally.

Until now, results taken at Peebles Hospital have been sent to the Caribbean Public Health Agency’s lab in Trinidad for a polymerase chain reaction test.

CARPHA has been offering free tests — commercially priced at $700 — to jurisdictions around the region trying to confirm whether or not Zika has reached their shores.

CARPHA originally only wanted to test five suspected cases in the Virgin Islands, but it ended up testing many more, according to Dr. Georges. As of last week, the BVI Health Services Authority had sent out 84 tests, not all of which have come back yet, he said.

The PCR testing process should see results returned electronically to the territory within a few days to two weeks, but delays have been affecting the lab in Trinidad, likely due to the sheer number of cases, Dr. Georges added.

The BVIHSA will continue to subsidise the cost of Zika tests, he said, but it will begin sending them to a different lab in Puerto Rico for the CDC Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (ELISA, for short) test.

While the PCR is most effective if blood is drawn within two to five days of symptom onset, the ELISA test is best administered two to 12 weeks after symptoms start. It can, however, be less accurate, having occasional problems with cross-reactivity, which means it has the potential to mistake Zika for another virus like dengue fever.

Still, Dr. Georges is confident in the ELISA’s reliability, and he plans to count any positive results from that test toward the territory’s overall totals.

The test, while not free, should cost under $20 with NHI, he said. Privately, it costs more than $180.

Dr. Georges added that NHI will cover the cost of additional ultrasounds for pregnant women who test positive for the virus.

Of the 25 confirmed cases, not all of them came out of the 86 tests sent to Trinidad. Some came from private clinics that have been sending tests to Puerto Rico, Dr. Georges said.

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