A caregiver of an elderly Zika patient in Utah has been diagnosed with the disease, leaving health officials stumped about how the virus was transmitted from patient to caregiver.
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The Utah Department of Health said it does not know how the caregiver, a family member of the patient, was infected with the Zika virus.
The unnamed patient died while infected with the virus and had an underlying condition, and it was unclear if the virus contributed to the death, according to the health department.
The virus has been known to spread only via mosquitoes or directly from person to person through sexual contact. The U.S. Centers for Disease Control and Prevention is investigating how the caregiver could have contracted the virus even if the caregiver did not go to a country with ongoing Zika virus transmission and did not have sex with a person known to be infected with the virus.
The CDC has reported at least 1,133 cases of Zika infections in the U.S. In virtually all those cases, people traveled outside the U.S. and became infected by mosquitoes abroad. In a small number of cases, the virus was transmitted through sexual contact in the U.S. There have been no cases of people being infected from mosquitoes in the continental U.S.