The Marshall Islands, a group of volcanic islands and atolls in the Pacific, closed its borders in March to fend off the coronavirus.
At the time, the government said the islands were already dealing with outbreaks of dengue fever and an "Influenza-like-Illness."
"A single-case of COVID-19 would be catastrophic to the health system," the government said at the time.
On Wednesday, the government announced that two workers arriving from the U.S. tested positive for the coronavirus at a U.S. military base on Kwajalein Atoll. The two cases ended the Marshall Islands' run as one of the few nations in the world with zero known coronavirus cases.
The pair — a woman, 35, and a man, 46 — arrived on a military flight Tuesday from Hawaii. The government said the two did not interact with members of the community, and both were asymptomatic when they tested positive.
"We can assure the public that these are strictly border cases and were discovered while these people were in quarantine, where they remain until this time," the government said.
There is no immediate risk of spread, it added.
Islands in the South Pacific were generally swift to isolate themselves during the start of the pandemic, leaving the majority of them unscathed.
The remote island nations of Kiribati, Micronesia, Nauru, Palau, Samoa, Tonga, Tuvalu and Vanuatu are believed to be still free of the virus.
The Solomon Islands recorded its first coronavirus case in early October.
In June, the Marshall Islands eased restrictions slightly, allowing U.S. military base workers to enter but requiring a three-week quarantine, according to The Guardian.
Ebon Atoll Mayor Marie Davis Milne has been critical of relaxing the border restrictions.
"What we were worried about has come true," Milne said Wednesday on Facebook. "Lives are going to be put on hold because a handful of people made the decisions they did for whatever reasons they did."
Reese Oxner is an intern on NPR's News Desk.
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