SALT LAKE CITY -- A Utah man who became the first person in the continental U.S. to die after being infected with the Zika virus passed it to a caregiver, creating a medical mystery about how it spread between them, health officials said Monday.
The caregiver is a "family contact" and has fully recovered, but officials did not give further details, including how the virus was transmitted.
"Our knowledge of this virus continues to evolve and our investigation is expected to help us better understand how this individual became infected," said Dr. Angela Dunn, deputy state epidemiologist at the Utah Department of Health. "Based on what we know so far about this case, there is no evidence that there is any risk of Zika virus transmission among the general public in Utah."
The man who died in late June caught the virus while traveling abroad to an area where mosquitoes are known to spread Zika and had an unusually high level of the virus in his blood, officials said -- "more than 100,000 times higher than seen in other samples of infected people," according to a CDC statement.
The exact cause of the death announced July 8 was not clear because the man was elderly and also had an underlying health condition.
He had Zika symptoms -- including rash, fever and pink eye -- but it's unclear if or how the virus contributed to his death, the Centers for Disease Control and Prevention said. The transmission to the caregiver was discovered after a doctor noticed Zika-like symptoms.
"The new case in Utah is a surprise, showing that we still have more to learn about Zika," said Dr. Erin Staples, a CDC medical epidemiologist on the ground in Utah. "Fortunately, the patient recovered quickly, and from what we have seen with more than 1,300 travel-associated cases of Zika in the continental United States and Hawaii, non-sexual spread from one person to another does not appear to be common."
Utah authorities have refused to release additional information about the man who died or where he traveled, citing health privacy laws.
The virus causes only a mild illness in most people. But during recent outbreaks in Latin America, scientists discovered that infection during pregnancy has led to severe brain-related birth defects.
It's spread mainly through the bite of a tropical mosquito.
No cases of mosquito-spread Zika have been reported in the continental United States, according to the CDC. Health experts think mosquito transmission probably will occur in the U.S., but the expectation is that it will be in low-elevation, sweltering places where the insect has been a steady problem - like southern Florida or southern Texas.
More than 1,300 Zika illnesses have been reported in the 50 states and the District of Columbia, including eight in Utah, according to health officials. Almost all were people who had traveled to Zika outbreak countries and caught the virus there.
But 14 were people who had not traveled to Zika zones but had sex with someone who had.
The CDC has also been tracking pregnant women infected with Zika, and says they have five reports of pregnancy losses because of miscarriage, stillbirth or abortion.