An elderly Utah resident who recently died after contracting Zika during a trip abroad appears to have passed the virus to a caregiver. The caregiver did not travel to a Zika-affected area or have sexual contact with anyone who did. And so far, Aedes mosquitoes—the species known to spread the disease—have not been found in Utah.
The findings raise the possibility that a third previously undiscovered route of transmission exists for Zika. It's the first virus ever that can be spread by both mosquitoes and sex, and that is capable of causing severe birth defects.
The deceased patient had extremely high amounts of virus—more than 100,000 times higher than seen in other samples of infected people—in his blood, according to the Centers for Disease Control and Prevention. It remains to be seen whether that number indicates a particularly virulent strain of the virus or simply that the patient was immune-compromised and thus unable to fight off the infection as a healthier person would.
The caregiver who contracted the virus has recovered.
The CDC has sent an emergency-response team to Utah to help figure out how the virus was transmitted from the elderly patient to the caregiver. In a press call this afternoon, CDC officials said it was too early to put forth any specific hypothesis, but that it was "extremely unlikely" that the virus had become airborne, or that it had developed the ability to transmit through a species of mosquito other than the Aedes. The CDC team is actively interviewing and testing family members and health care workers who came into contact with the deceased patient.
Utah health officials have been trapping and testing other mosquitoes for Zika, including the Culex species, which carries West Nile Virus, just to be safe. But based on what they know so far, they say the risk of Zika transmission among Utah residents remains low.
The CDC has recorded 1,306 cases of the Zika virus in the United States, including 346 cases among pregnant women. So far, none of those reported cases involve local mosquitoes actively transmitting the virus.
Zika is largely inconsequential for most people but can be devastating in pregnant women because of its ability to cross the placenta and cause microcephaly and other severe birth defects.
"The new case in Utah is a surprise, showing that we still have more to learn about Zika," said Erin Staples, M.D., the CDC's medical epidemiologist on the ground in Utah. "[But] from what we have seen with more than 1,300 travel-associated cases of Zika in the continental United States and Hawaii, nonsexual spread from one person to another does not appear to be common."
