A person who cared for a Zika-infected relative in Utah also got the virus, but exactly how it was transmitted is a medical mystery, health officials announced Monday.
The tropical mosquito that mainly spreads Zika isn't found in the high-altitude area with cold winters where the two lived, Salt Lake County Health Department officials said. They didn't have sexual contact, which is how the virus is typically spread between adults when there's no mosquito bite or mother-to-child transmission.
"The new case in Utah is a surprise, showing that we still have more to learn about Zika," Centers for Disease Control and Prevention medical epidemiologist Erin Staples said.
The caregiver has fully recovered, but authorities did not give further details. The person cared for an elderly man who contracted the disease overseas, where mosquitoes are known to spread Zika and who became the first Zika-infected person to die in the continental U.S.
The caregiver did not travel to an affected area, but it's possible that a mosquito came back with the relative, perhaps in a suitcase, CDC Director Tom Frieden said.