SALT LAKE CITY (AP) — A source has told The Associated Press that a Utah man caring for his father contracted Zika virus in a case that has baffled health officials.

The virus is typically spread by mosquitoes and also has been transmitted sexually. The case is unusual because the son didn't travel to an area where mosquitoes are known to spread Zika or have sex with anyone who did, so it's unclear how he got sick. He has recovered. His father caught Zika overseas and died after returning home with an unusually high level of the virus in his system.

His was the first death of a Zika-infected person in the continental U.S. The person who confirmed the relationship between the two is familiar with the case and spoke Tuesday on the condition of anonymity because the person isn't authorized to discuss the case by name.

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