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If you’ve been keeping up with health news over the past two years, you would have heard about the Zika virus, spread by the bite of a certain type of mosquito.

Zika can also cause the birth defect microcephaly, where a baby’s head is considerably smaller than the body, as well as miscarriages.

But now, new research suggests that the virus is not the direct cause of these birth defects.

Immune response to blame

The virus itself might not directly cause the miscarriages and birth defects that have been associated with the notorious virus, a new study in mice suggests.

Instead, the ravaging effects of Zika infection on a developing foetus appear to stem from the immune response of the expecting mother, researchers said.

The study was published in the journal Science Immunology.

Lab mice bred without a key step in their immune response wound up birthing pups that survived Zika infection, while normal mice either lost their pregnancy or produced very underweight pups, the study found.

“The antiviral response generated in response to Zika infection is causing the miscarriage of the foetus, as opposed to the virus itself,” according to senior researcher Akiko Iwasaki. She is a professor of immunobiology at the Yale University School of Medicine.

Iwasaki and her colleagues are now investigating whether a woman’s immune response also causes some or all of the birth defects associated with Zika.

What the study entailed

The lab study revolved around a key signalling protein for the immune system, called type 1 interferon. The body produces type 1 interferon in response to a viral infection, and the protein in turn mounts a rapid and potent multipronged defence intended to keep the virus from spreading.

The researchers suspected that an interferon deficiency might explain why some pregnancies are more affected by Zika infection than others – because, in those cases, the immune system would not respond as strongly to the infection.

To test this theory, they bred lab mice that lacked receptors for the immune protein.

“We thought the foetuses missing this interferon receptor would be more susceptible to death from Zika infection, and the foetuses that had the receptor signalling would be protected,” Iwasaki said.

“What we found was quite the opposite,” she said. “The foetuses unable to respond to interferon survived infection, and those that had the receptor, either they all died or were very small.”

Mice and humans share many biological characteristics, which means that the response is likely to be the same in people, Iwasaki said.

Further investigation needed

However, research in animals frequently doesn’t produce similar results in humans.

Exploring the matter further, the researchers cultured human placental tissue in the lab and then exposed the tissue to interferon, Iwasaki said. The cells wound up becoming deformed, featuring abnormal, knotty structures that previously have been linked to high-risk pregnancies.

According to Dr Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, these findings open up a potential avenue for protecting the foetus of a woman infected with Zika.

“The consequences of any infectious disease are the result of an elaborate interaction between the immune system and the microbe, and it appears that Zika’s impact on the foetus is another example of this phenomenon,” he said. Adalja was not involved with the study but was familiar with the findings.

“Such a finding provides some basis for understanding if a therapeutic approach in which the effects of interferon are blocked might be beneficial,” Adalja said.

A new understanding

Iwasaki, though, thinks this emphasises the need for a Zika vaccine because “it’s very tricky to treat women if they’re already infected with the Zika virus,” she said.

Instead, she thinks the real value in the study is a new understanding of how any viral infection might influence the health of a pregnancy.

“This has implications for other viral infections as well, because the same response would be generated for virtually every viral infection,” Iwasaki said.

In particular, women with autoimmune disorders trying to have a baby could benefit from this research, Iwasaki said. These women aren’t actually fighting off a virus, she explained, so interrupting their interferon immune response would not expose them to any harm and could preserve the health of their baby.

“If elevated interferon is a more general underlying mechanism for pregnancy complications, we might be able to interfere with the interferon signalling,” Iwasaki said. “Because there’s no viral infection to worry about, we might be able to help pregnancy carry through to term in those women who are suffering from autoimmune diseases.”

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My parents always told me it wasn’t a good idea to brag about something unless I was really exceptional at it. The advice kept me humble and grounded, and it's been the way I've lived my life ever since. So when I say I this, I hope you'll believe me: I am an expert at coming back from the dead—because when I was 24 years old, I got run over by 8 wheels of an 18-wheel truck.

It happened early on a fall morning. I had hopped on my bike for a 10-mile ride, to burn off some calories from an overindulgent weekend. It was a lovely morning, bright and crisp. The leaves on my Brooklyn block were just starting to turn yellow. I was closing out my ride when I saw the sun starting to rise over the low, brick industrial buildings on a busier street near my apartment. I thought that catching that sunrise would make the morning so incredibly perfect.

I was staring straight at it when I stopped at a red light, and didn’t pay too much attention to the truck beside me. The driver hadn't put his turn signal on, and I had signaled that I was turning. I was sure he was aware of me, and I was safe to chase that morning-maker of a sunrise.

I took my turn wide and easy, and then I noticed that the truck wasn't going straight. He was also taking the turn, and our paths were going to collide. Before I could register what was happening, I felt like I was tumbling, and found myself pinned beneath the truck's first four wheels. I heard my bones cracking, and watched as the tires rolled over my body. I kept my eyes open as the next set of wheels came for my already crushed middle. I was too terrified to blink.

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The mind is a miraculous organ. Mine went into full psychological triage mode. I thought that I couldn’t close my eyes, because if I did, then I would somehow fall into a deep darkness where I had no control. So I kept them wide open. I also amazingly remembered my mom’s cell phone number and my home number, so the bystanders who had witnessed the accident could call my parents.

But the most incredible thing that my mind did was remember something my best friend, who's a nurse, had told me: that if I ever needed an ambulance and the closest hospital wasn’t very good, I had patient rights and could ask to be taken elsewhere.

When the EMTs arrived, they found themselves talking to a woman with tire tracks on her stomach requesting to not go to the hospital nearby, but instead to the best hospital. I watched as they looked at each other dumbfounded, sure that I would die before I made it to any hospital. But I was insistent. My brain wanted my body to live, and it was willing to be pushy to make it happen.

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Beating the expectations of the EMTs, I remained conscious during the ambulance ride to the “best” hospital. As I was being wheeled into the ER, I asked the closest doctor if I was going to die. She looked at me sadly and said it didn’t look good, but she was going to try.

I am not sure why my body didn’t just give in at that moment. Or in all the moments that followed during the 10-hour surgery I went through. Amazingly, it didn’t. Although it came incredibly close.

Four hours into the surgery, I had been given about 8 pints of blood, but my blood wouldn’t clot so I kept bleeding out. The doctors told my family that if I didn’t start clotting within the next hour, they were going to have to let me die. Amazingly with 15 minutes left until my literal “deadline,” I began to clot.

When I woke up from surgery, my life was unrecognizable to me. I had broken all of my ribs, fractured my pelvis in five places, punctured my lungs, and torn a hole in my bladder. I couldn’t feel my body from my ribcage down, and my bike's gearshift had dug itself into my right oblique muscle, creating a hole where the side of my stomach used to be.

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I spent the next two months in the hospital, working to heal my broken body. When I was released from the hospital into my parents' care, I lived in the family room of the house I grew up in, sleeping on a rented hospital bed for another four months. I did intensive physical therapy every day. After an unbelievable amount of practice, and thanks to endless patience from my friends and family, I finally walked by myself eight months after the accident.

In the early stages of my recovery, I spent the majority of my time grasping at the person that I had been before the crash, trying so hard to become her again. But at some point, I realized she didn’t exist anymore. I wasn’t that carefree 24-year-old with no understanding of how challenging and precious my life was.

That's when I stopped focusing on the parts of my life that I had lost, and started to focus on what I had gained: a deep gratitude for a life that I almost didn't get the chance to live. I began to feel moments of overwhelming joy, like when my mom wheeled me out to the backyard so I could feel the first snowflakes of winter fall on my tongue; or the day my feet touched the floor for the first time in weeks; and whenever I decided to have champagne just because. The beauty of these little moments would have been lost on me only a few months before.

I don’t call myself an expert on surviving just because my body found a way to keep itself alive—but also because I fought to bring my life from a place of brokenness to a place of joy. For me, surviving isn't just not dying. It's also giving yourself the gift of truly living.

You can read more of Katie McKenna's story in her inspiring memoir, How to Get Run Over By a Truck ($16; amazon.com).