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Puerto Rico declared its Zika epidemic over on Monday, saying transmission of the virus on the island has fallen to relatively low levels.

In a statement, the territorial government said there have been only about 10 cases of Zika reported in every four-week period since mid-April, down from more than 8,000 cases in four-week periods at the same time last year.


The announcement seemed to be an attempt by the government of the financially troubled territory to draw a line under an outbreak that has hit the island — in terms of both disease counts and economic fallout — harder than any other part of the United States.

Puerto Rico had diagnosed more than 40,000 confirmed cases of Zika infection as of May 20, the most recent date for which data are available. Thirty-eight cases of Zika-induced birth defects have been recorded, although outside experts believe that figure is a substantial underestimate of the problem in the territory.

The Centers for Disease Control and Prevention has reported 80 affected pregnancies among 1,579 women infected in pregnancy who have given birth in the U.S. In Puerto Rico, 3,703 women — more than double the U.S. total — were diagnosed with Zika during their pregnancies, but the affected pregnancies number is half that seen in the 50 U.S. states.


STAT reported earlier this spring that U.S. health officials were concerned that Puerto Rico was not counting cases of Zika-related birth defects correctly, the effect of which was to underplay the scale of the problem there.

Concern about the territory’s approach to counting Zika cases strained the relationship between the CDC and Puerto Rico’s department of health, which received CDC grants of $9.5 million to establish and operate a pregnancy registry aimed at charting Zika’s impact on newborns in the territory.

For a time, Puerto Rican officials refused to meet with their CDC counterparts. And last October, CDC stopped reporting Zika figures from Puerto Rico, saying it was not using the agreed-to surveillance criteria to count cases. The CDC still does not report Puerto Rico’s Zika data.

Monday’s statement from Puerto Rico appeared aimed at glossing over the dispute; it made multiple references to how the department of health and the CDC have been working together to manage the outbreak and protect the public.

“In coordination with the CDC, we have put in place a comprehensive program focused on preparation, prevention, precaution and surveillance,” said Dr. Rafael Rodriguez-Mercado, Puerto Rico’s secretary of health. “These efforts can be used as a model for other regions experiencing local Zika virus transmission.”

The CDC declined STAT’s request for an interview regarding Puerto Rico’s announcement. However, the agency sent a written statement from CDC Acting Director Dr. Anne Schuchat, who cautioned against thinking the threat has passed.

“We are pleased that the peak of the Zika virus outbreak in Puerto Rico has come to a close,” Schuchat said. “However, we cannot let our guard down. CDC will continue to focus on protecting pregnant women and work closely with PRDH to‎ support comprehensive Zika surveillance and prevention efforts on the island.”

The CDC is not immediately lifting its advice to pregnant women to avoid travel to the territory.

“CDC is still reviewing recent surveillance data in Puerto Rico to determine if the travel notice can be removed. At this time, there are no plans to change CDC’s travel recommendations for Puerto Rico,” a spokesperson said in an email.

As the Zika virus swept through the Americas last year, the CDC urged pregnant women to avoid travel to a lengthening list of countries and locales where the virus was spreading.

While transmission in a number of these places seems to have abated, the agency has removed very few places from the avoid-while- pregnant list.

Three places — American Samoa, New Caledonia and Saint Barthelemy — were removed from the list after transmission was deemed to have stopped there. And Brazil — which declared its Zika health emergency over in mid-May — also saw a change of status.

Currently low-level transmission is believed to be occurring there; while it no longer qualifies as an epidemic, Zika transmission is now considered endemic in Brazil. But the continued risk of contracting Zika means the CDC still recommends pregnant women avoid travel to Brazil.