It's been thought that the Zika virus spreads only through mosquito bites or sexual contact. But someone in Utah appears to have caught Zika another way — while caring for an elderly family member infected with the virus.
"The new case in Utah is a surprise, showing that we still have more to learn about Zika," Erin Staples, a medical epidemiologist at the federal Centers for Disease Control and Prevention, reported Monday.
Health officials stressed to reporters in a press briefing that mosquitoes remain the main way that Zika spreads. And there is no evidence at this point that the virus can be spread from one person to another "by sneezing or coughing, routine touching, kissing, hugging or sharing utensils," Dr. Satish Pillai, the CDC's incident manager, told reporters.
"However, there's a lot we don't know about Zika virus, and we are still doing a lot of investigation into whether Zika can be spread from person to person through contact with a sick person," Pillai said.
"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," Staples said.
The family caregiver who became infected quickly recovered and is being interviewed, along with other family members, by federal and state investigators to try to determine the route of viral transmission in this case.
Health care workers involved with the care of the elderly patient who is believed to have spread the virus are also being tested for Zika, the CDC said. And investigators are testing mosquitoes in the area, although there's no sign so far that any local insects are carrying the virus.
The elderly person caught Zika while traveling to a country where the virus is known to be spreading, according to state and federal health agencies. That patient died in June of unknown causes, the health officials said.
Tests have already shown that the deceased elderly patient had "uniquely high amounts of virus" in the bloodstream, according to a CDC statement. The level of virus was more than 100,000 times higher than seen in other samples of infected people, according to the CDC.
The significance of those high levels of virus remains unclear, but officials told reporters that could have been an important factor in how the virus spread.
In a written statement, the Utah Department of Health said the infected caregiver in the family "has not recently traveled to an area with Zika and has not had sex with someone who is infected with Zika or who has traveled to an area with Zika."
"Our knowledge of this virus continues to evolve and our investigation is expected to help us better understand how this individual became infected," Dr. Angela Dunn, the Utah deputy state epidemiologist, said.
There is "no evidence of any risk of Zika virus transmission among the general public," she added.
The Zika virus can cause serious birth defects when pregnant women get infected. The virus can also cause neurological complications in adults in rare cases.
Mosquitoes have spread the virus widely throughout Latin America and the Caribbean.
No known cases of mosquito-borne Zika virus infections have been reported in the United States. Zika has spread through sexual contact in the United States in a small number of cases. Last week, the CDC reported the first known case in which a woman spread the virus to a man through sexual contact.
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