July 19, 2016 12:08 pm

Zika virus: Scientists map mom to fetus transmission in 1st detailed explanation

A woman who is six months pregnant shows a photo of her ultrasound at the IMIP hospital in Recife, Pernambuco state, Brazil, on Wednesday. Scientists are trying to figure out how Zika virus may be affecting fetuses.

Brazil, on Wednesday. Scientists are trying to figure out how Zika virus may be affecting fetuses. Felipe Dana/AP

Health officials have warned women to avoid pregnancy in areas of the world grappling with Zika virus as they piece together how the disease can cause brain damage in a growing fetus.

The virus’ path from infecting an expectant mom to her unborn baby hasn’t been clear, but for the first time American scientists say they’ve mapped out two potential routes.

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READ MORE: First international clinical study on Zika virus vaccine set for Quebec City

Zika virus could be transmitted from mom to fetus through the placental route, only in the first trimester, or through breaking into the amniotic sac that only becomes available in the second trimester, according to University of California doctors out of San Francisco.

READ MORE: These are the tell-tale symptoms of Zika virus, according to a new case study

The West Coast doctors are the first to offer a thorough illustration as to how the mosquito-borne virus could make its way to a fetus.

“Very few viruses reach the fetus during pregnancy and cause birth defects. Understanding how some viruses are able to do this is a very significant question and may be the most essential question for thinking about ways to protect the fetus when the mother gets infected,” study co-author, Dr. Lenore Pereira, said in a university statement.

Handfuls of warnings to pregnant women have been doled out in light of Zika virus.

Zika virus first appeared in Brazil in May 2015. Months later, health officials noted a rise in birth defects in the country.

There’s been a 20-fold increase in a rare defect called microcephaly, in which newborns are born with irregularly small heads and underdeveloped brains.

READ MORE: What doctors know about how Zika virus potentially spreads

So far, officials in Brazil, Jamaica, Ecuador, Honduras and Colombia have urged their citizens to delay pregnancy until 2018 as doctors better understand the virus’ mechanisms. In the U.S., the Centers for Disease Control advised pregnant women against travelling to Latin America and the Caribbean.

The California scientists, in the latest study, say that Zika infects several different cell types inside and outside of the placenta. It seeps into the fetal membrane and the cells around the baby’s amniotic sac, they say. (Most viruses have a hard time crossing into the placenta, but the doctors think Zika can.)

Their guess is that Zika could affect a developing baby not just through the placenta, but through these other membranes, too. The virus latches onto placental cells called TIM1, based on their theory. They also guess that certain cells around the amniotic sac are vulnerable to Zika, pushing through the sac’s membrane.

“The most severe birth defects associated with Zika infection – like microcephaly – seem to occur when a woman is infected in the first and second trimester. But there may be a range of lesser but still serious birth defects that occur when a woman is infected later in pregnancy,” Pereira said.

READ MORE: Here’s what Zika virus symptoms look like in pregnant women

There was a silver lining in the research: the doctors learned that duramycin, an antibiotic that bacteria produces to fight off other germs, could help against Zika.

For the most part, duramycin is dubbed as an older generation antibiotic. It’s commonly used in animal testing and in trials for cystic fibrosis treatments.

But it’s worked in small experiments against dengue and West Nile, for example. The scientists say that duramycin “efficiently” blocked infection in placenta cells in the first trimester.

READ MORE: Canadian researchers develop disease outbreak surveillance

If you’re travelling to affected regions, health officials recommend that you consult with your health-care provider six weeks before you travel.

To protect against bug bites, they say you should cover up with light-coloured, long-sleeved shirts and long pants. Insect repellant and bed nets, also treated with insecticide, are also recommended.

Read more about safety precautions here.

Read the full findings published Monday night in the journal Cell Host and Microbe.


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