Puerto Rico has recorded 10,690 laboratory-confirmed Zika infections, prompting the federal government Friday to declare a public-health emergency aimed particularly at protecting pregnant women and children from an outbreak spreading across nearly the entire island.

Health and Human Services Secretary Sylvia Mathews Burwell determined that the epidemic constitutes an emergency of national significance under Section 319 of the Public Health Service Act. The formal declaration gives Puerto Rico greater flexibility to direct federal funds toward mosquito control, surveillance and medical services for women at risk of infection and infants who may face severe birth defects.

The action follows evidence that transmission is accelerating. Puerto Rico’s health department said confirmed infections had nearly doubled from the 5,582 identified through early July. Because most Zika infections cause no symptoms, officials believe laboratory totals capture only a fraction of the virus circulating in a territory of 3.5 million people.

An outbreak reaching almost every municipality

A detailed Centers for Disease Control and Prevention report published last week found confirmed or presumptive infections among residents of 77 of Puerto Rico’s 78 municipalities. Of 23,487 people evaluated from November through July 7, researchers identified 5,582 infections, including 672 pregnant women.

The rate of positive tests rose rapidly as mosquito season intensified. Among symptomatic men and nonpregnant women, the share testing positive increased from 14 percent in February to 64 percent in June. Among symptomatic pregnant women, it climbed from 8 percent to 41 percent. Those trends, the CDC said, warranted intensified mosquito control and personal protection.

The growing number of infected pregnant women is the central reason for the emergency. Zika infection during pregnancy can cause microcephaly and other severe fetal brain abnormalities. The virus has also been associated with Guillain-Barré syndrome, a neurological disorder that can cause paralysis. Puerto Rico is monitoring infected women and their children through a dedicated pregnancy surveillance system.

Emergency authority and constrained resources

HHS’s declaration does not carry a large new appropriation. Instead, it allows officials to make existing resources more flexible, including permitting Puerto Rico to apply for temporary reassignment of personnel funded through federal public-health programs. It can also support expanded services for pregnant women and children through local health centers.

The declaration appears on HHS’s official registry of public-health emergencies, placing the outbreak alongside disasters and disease events that require extraordinary federal coordination. Burwell said the virus poses a significant threat to the commonwealth’s public health, especially to women who are pregnant and children born to infected mothers.

That flexibility matters because Puerto Rico is in a deep fiscal crisis, with health agencies confronting the epidemic while the government struggles under roughly $70 billion in debt. Congress left Washington for its summer recess without resolving competing Zika funding bills. Federal health agencies have warned that money redirected from other programs is running short.

Reuters reported Friday that the declaration came as the island’s confirmed count reached 10,690. The figure underscores how quickly the outbreak has moved beyond the earlier surveillance period analyzed by the CDC.

Pregnancy prevention and mosquito control

There is no vaccine and no specific treatment for Zika. Public-health efforts therefore depend on preventing mosquito bites, reducing mosquito populations, testing pregnant women and limiting sexual transmission. The Aedes aegypti mosquito thrives in warm urban environments and breeds in small collections of standing water, making island-wide control extraordinarily difficult.

CDC Director Dr. Thomas Frieden has called Puerto Rico’s outbreak both a challenge and a crisis. In March, he warned that cases were doubling weekly and that hundreds of thousands of residents—including thousands of pregnant women—could eventually be infected. Officials are urging residents to use insect repellent, wear protective clothing, install screens and remove standing water.

The response also includes distribution of Zika prevention kits to pregnant women, expanded access to contraception for women who wish to delay pregnancy, and testing during the first and second trimesters even when a woman has no symptoms. That last measure is essential because asymptomatic infection can still threaten a fetus.

Blood safety is another concern. Puerto Rico halted local blood collection earlier this year and began importing screened supplies while federal authorities evaluated testing. By June, the CDC was detecting an increasing rate of infected donations, though screening meant the blood supply posed little known transfusion risk, according to contemporaneous reporting on the program.

A widening federal response

The emergency declaration is one element of a broader response that includes CDC laboratory support, mosquito surveillance, clinical guidance and research into vaccines and diagnostics. In April, when Puerto Rico had reported 683 confirmed infections, the territory also recorded a rare Zika-associated death involving severe thrombocytopenia, as described in reporting on the CDC’s findings.

Those early numbers have now been overtaken many times over. The central uncertainty is not whether transmission will continue, but how many infections can be prevented before more pregnancies are affected. Mosquito control has proved difficult, proposed aerial spraying has met public resistance, and the island’s financial condition limits local capacity.

Federal emergency authority can loosen administrative constraints, but it cannot by itself eliminate breeding sites, restore depleted budgets or provide the billions in national Zika funding still stalled in Congress. The declaration nevertheless signals that Puerto Rico’s outbreak is no longer being treated as a localized mosquito problem. It is a national public-health emergency centered on the consequences that may not be fully visible until infected pregnancies reach delivery.