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Could a mysterious case of Zika point to a new mode of transmission?




Zika is primarily spread through this mosquito species, Aedes aegypti.
Zika is primarily spread through this mosquito species, Aedes aegypti.
Andre Penner/AP

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Yesterday health officials announced what appears to be a bit of a medical mystery.

A person who cared for a Zika-infected relative in Utah also contracted the virus,  but it's unclear how that happened.

The original patient contracted the disease overseas, but the caregiver didn't travel to a Zika affected area and had no sexual contact with a Zika-infected person, so how did they contract the virus?

Dr. Claire Panosian Dunavan, professor of medicine and infectious diseases at the David Geffen School of Medicine at UCLA, joined Take Two to talk through some of the possibilities.

Up until now what's been the consensus on the various ways in which Zika could be transmitted?

Mosquitos are the primary mode of transmission, but body fluids (semen and blood) would also be capable of transmitting the virus. That means sexual transmission, possibly blood transfusions. But then there have been these emerging facts that the virus can also be present in urine and saliva. It's not assumed that that would be a very common way for transmission to occur.

What are the chances that a mosquito with Zika might have been buzzing around this part of Utah?

It's my understanding that Aedes mosquitos are not found in northern Utah, but this shines a light on the fact that we have not been doing extremely detailed surveillance for mosquitos in this country, so at this time somebody is taking a look and doing trapping and finding out if they might have been wrong. Having said that, it does not seem to be a climate where it would support a lot of mosquito-borne transmission of Zika.

What we do know about this case in Utah is that the original patient was an elderly man who became the first Zika-infected person to die in the continental U.S. He seems to have picked up Zika while traveling abroad. It's unclear if that man died because of his age or because of another health condition he suffered from, but what does this tell us when we then find out that his relative who cared for him then also got Zika?

Well, you've already highlighted some of the intriguing unanswered questions. It's also my understanding that this man had some chronic illnesses and that it was determined that he had a very high level of virus in his blood, which means he would be what we would call a "super spreader" in other viral diseases such as SARS or MERS, so presumably his body fluids had more virus. Now, the next mystery is how his family member, possibly his son, who seems to have been a caregiver, could have been exposed if he were not bitten by a mosquito. No sexual transmission is assumed in this case. But, if you picture a complex medical scenario, say he was on dialysis, there would be an opportunity for blood borne transmission just because of the complexity of the care. What the CDC has said is that sneezing, kissing, coughing, shared utensils, etc. are likely to transmit Zika. So this one case may just be a very odd outlier for reasons that we still don't yet know because he haven't been given many details.

There's been some speculation that this man who traveled abroad could have brought a Zika-infected mosquito back to the U.S. in his luggage or clothing. How likely is that scenario, do you think?

I find that kind of totally implausible. But, you know, I've been wrong. Everybody's been wrong with this virus. There have been many twists and turns since we started paying attention to it months ago.

How do you think this caregiver contracted the virus?

I had to guess, it would be that the elderly man who eventually died had a lot of viral particles in his body fluids and that somehow his caregiver was exposed. It could have been a needle stick, it could have been something really quirky. I sure would like to have more details from CDC, and I'm sure they will eventually give them, but this is their usual m.o. They kind of slowly release the facts that help to illuminate the science.

How concerned should people be about the possibility of a new mode of transmission for the Zika virus? What do they need to know?

I'm frankly more concerned about getting the most important messages to the public, as opposed to worrying about a new form of transmission from a man who had a very high amount of virus in his blood. I'm still not sure how many people who have traveled to Zika endemic areas realize that they may be completely well and yet a man would need to use a condom and practice protected sex for 8 weeks after returning. I'm not sure how many people who've traveled to an endemic area know that they should be using mosquito repellent for 3 weeks after they've returned back.

These most-important messages are pretty difficult to present to the public because it's not intuitive. At the time, sure, if it were an airborne virus, that would lead to a whole other level of messages but I just don't see that happening. I do not think that this is a virus that will be easily spread by sneezing, kissing, coughing, etc. So it's all about priorities right now.

Questions and responses have been edited for clarity.