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A new report suggests the first person who died while infected with Zika virus in the United States actually succumbed to the infection, not a previous illness.

The unidentified man died in July in Salt Lake City after contracting the virus while traveling in Mexico. At the time of his death officials suggested the man died “with” Zika — that his other ailments were likely the actual cause of his death.


But the medical team who cared for him at University of Utah Health Care reported on the case Wednesday in a letter published in the New England Journal of Medicine. There, they made clear that they believe it was the Zika infection that caused the man’s death.

“What this taught me is … the spectrum of disease is quite large and there may be a small number of people — whether it’s because of other weakening conditions or unknown factors — [that] could have a fulminant outcome,” Dr. Sankar Swaminathan, the hospital’s chief of infectious diseases, told STAT.

The head of the Center for Disease Control and Prevention’s Zika response concurred with the assessment of what happened in this case.


“In most cases, fatal Zika is associated with underlying illness. However, this may not always be the case,” Dr. Lyle Petersen, director of the CDC’s division of vector-borne diseases, said in an email.

Before the man, 73, was infected with Zika, he had been treated for localized prostate cancer with radiation and hormone-suppression therapy. But the treatment was considered successful; the man was in good health and not on any medication other than the hormone therapy when he contracted Zika, Swaminathan said.

The man had previously been infected with dengue, a closely related virus — a fact that raises a question experts have asked about Zika infection.

There are four strains of dengue, and it’s known that people infected with one strain can have a more serious, even life-threatening infection if they contract a second strain of the virus later. That phenomenon is called antibody-dependent enhancement or ADE.

Experts have wondered if people who contract Zika after having had dengue might be more likely to have severe disease — or in the case of pregnant women, more likely to give birth to a baby with Zika-induced birth defects.

Swaminathan said it’s one of the possible explanations for why this man had such a fatal infection.

“ADE may have played a role, but there’s no way to know how much of a role that had here,” he said.

The man was originally from Mexico and had traveled there for a visit. The genetic sequence of Zika viruses found in his blood were a close match to viruses that had circulated in Mexico.

About a week after returning from his trip, he was taken to the hospital gravely ill. He had sepsis — a dangerous condition where the body’s infection-fighting response overreacts and overwhelms the patient. It can lead to multi-organ failure, which is what happened in this case.

Sepsis is very difficult to treat. And despite the efforts of his doctors, the man died four days after being admitted to hospital.

For reasons that aren’t yet known, the man’s body was teeming with Zika viruses while he was dying. His son, who visited him in the hospital and wiped fluid from his eyes, later contracted Zika.

The second man had not traveled outside the US and had not had sex with someone who had traveled to a place where Zika was spreading. Mosquito traps set around both men’s houses failed to turn up Aedes aegypti mosquitoes, the species known to transmit Zika.

Swaminathan said it’s still not clear how the son became infected, but the supposition is that it was through contact with tears or sweat. The man had helped to reposition his father in bed at a point.

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