Has the Zika virus mutated? According to a report out of Utah, A man who became the first person in the United States to die after being infected with the Zika virus passed it to a caregiver, creating a medical mystery regarding how the virus spread between the two.

According to official reports from the Salt Lake City-County¬†Health department, The two people did not have sexual contact and the type of mosquito that mainly spreads the virus is not found in the high-altitude area where they live. The caregiver is a “family contact” and has fully recovered from the virus but officials are still left baffled on 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.”