CDC officials reported that health officials are investigating how the second person became infected, interviewing and conducting blood tests of family members and healthcare workers who may have had contact with the man, who died in June.
Health officials are also trapping mosquitoes in Utah and testing them for the virus to assess the potential for local transmission. However, the two species known to transmit Zika — Aedes aegypti and Aedes albopictus — are not known to be present in Utah.
“The new case in Utah is a surprise, showing that we still have more to learn about Zika,” Erin Staples, a physician-researcher and the CDC’s medical epidemiologist in Utah, said in a press release.
Of the more than 1,300 cases reported in the continental United States as of July 13, the Utah case represents the first possible person-to-person transmission not involving sex. At least 14 cases were sexually transmitted, and one was acquired by exposure in a laboratory.
According to the CDC, lab tests showed the man who died had unusually high amounts of Zika virus — more than 100,000 times higher than seen in other samples of infected people — in his blood. As with other infectious diseases, a high viral load makes transmission easier.
The patient who acquired Zika from the deceased Utah man has since recovered. Benjamin Haynes, a CDC spokesman, said the second man had not traveled to areas where the virus is locally transmitted, nor has he had sexual contact with someone who has traveled to an area where Zika is spreading.
Zika is primarily spread through the bite on an infected mosquito, although it also can spread via sexual transmission, blood transfusion and from mother to baby during pregnancy.