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The United States, on Friday, reported its first Zika-related death, which occured in the Puerto Rica territory in February this year.

The victim was a 70-year-old man from Puerto Rica, which is one of the worst-hit territories of the U.S., the New York Times reported.

The man died from internal bleeding due to an auto immune reaction to the Zika infection, the U.S. Centers for Disease Control and Prevention (CDC) said.

"The man who died was a resident of the San Juan area. He fell ill with fever, rash and other typical Zika symptoms early this year," Tyler M Sharp, a CDC epidemiologist working in Puerto Rico, was quoted as saying by the NYT.

Sharp said that even as his illness resolved, he had bleeding manifestations after which he was hospitalised.

He added that the patient died within 24 hours of being hospitalised.

He is said to have been suffering from a condition called immune thrombocytopenic purpura, which is similar to Guillain-Barré Syndrome (GBS).

The doctors said that the Zika infection triggered his immune system to produce antibodies that attacked his own cells.

"In Guillain-Barré, they attack nerve cells, while in this case, they attacked the platelets, which cause the blood to clot," Sharp said.

He added that the death was not reported earlier because it took time to be sure Zika was in fact caused the victim's death. "We had to check with family members, his personal physician and the doctors who managed him to be sure he didn't have something else going on," Sharp said.

Puerto Rica's health secretary Ana Ríus said that the region has so far reported 683 cases of Zika infection, and about 89 of the affected people are pregnant women. She added that 14 of those Zika-infected women have already given birth, and all their babies are healthy.

Brazil, which is the other Zika-affected country has reported three deaths from the infection till now. Although deaths from Zika are rare, the World Health Organization declared Zika as public health emergency on Feb. 1, 2016.

According to CDC, 426 cases of Zika virus were reported in the 50 U.S. states, mostly in travellers who had been to the affected areas. Scientists are also studying the other modes of Zika virus transmission such as sexual relations and blood transfusion.