The mosquito-borne Zika virus might be a disaster waiting to happen in the continental United States. But in Puerto Rico, a U.S. territory, the threat is rapidly on its way to becoming a terrible reality. Public health officials should be given all needed assistance from the federal government for prevention and treatment.

Twenty percent of Puerto Ricans — about 700,000 people — are expected to become infected with the virus, The Washington Post reported Monday.

At present 117 people in Puerto Rico have been determined to be infected by Zika, which has been linked to birth defects in Brazil and elsewhere. But the infection rate is expected to escalate rapidly with local conditions that favor mosquito breeding, and because of limited resources for public health agencies, which are hamstrung by the continuing budget crisis in the territory.

The grim prognosis is shared by officials with the Centers for Disease Control as the agency continues to increase its presence on the island to meet the escalating threat.

“I don’t think we’re going to be able to stop the Zika outbreak,” CDC official Steve Waterman told the Post.

The hazard is compounded by the lack of window screens in most housing on the island, the presence of ample breeding grounds for mosquitoes, such as discarded auto tires, and the absence of a pesticide that is effective against the mosquitoes.

One eventual consequence of a heightened rate of infection on the island will be increased risk on the mainland, as people fly back and forth to the island on daily flights. Puerto Rico also is a favorite stop for cruise ships.

Zika is expected to be a problem for the United States, as well, but with the early difficulties experienced in Puerto Rico, the threat has suddenly become less theoretical.

The Obama administration should provide the necessary assets to forestall a public health disaster for hundreds of thousands of Puerto Ricans.

By doing so, it would also lower the Zika risks for U.S. residents elsewhere.

Meanwhile, mosquito abatement measures should become a major priority here in South Carolina — and the rest of the nation — as spring approaches.