New evidence suggests Zika virus can cross placental barrier, but link with microcephaly remains unclear

February 18, 2016, Lancet
Transmission electron micrograph (TEM) of Zika virus. Credit: Cynthia Goldsmith/Centers for Disease Control and Prevention

Zika virus has been detected in the amniotic fluid of two pregnant women whose foetuses had been diagnosed with microcephaly, according to a study published today in The Lancet Infectious Diseases. The report suggests that Zika virus can cross the placental barrier, but does not prove that the virus causes microcephaly, as more research is needed to understand the link.

Researchers also analysed the whole genome of the found in the two and confirmed that the virus is genetically related to the strain identified during an outbreak of Zika virus in French Polynesia in 2013.

"Previous studies have identified Zika virus in the saliva, breast milk and urine of mothers and their newborn babies, after having given birth. This study reports details of the Zika virus being identified directly in the of a woman during her pregnancy, suggesting that the virus could cross the placental barrier and potentially infect the foetus" said Dr Ana de Filippis, lead author from the Oswaldo Cruz Institute in Rio de Janeiro, Brazil.

The placental barrier is made up of layers of tissue in the placenta and regulates the exchange of substances (including infections) between the mother and foetus. The amniotic fluid is the protective liquid around the foetus.

Dr de Filippis added "This study cannot determine whether the Zika virus identified in these two cases was the cause of microcephaly in the babies. Until we understand the biological mechanism linking Zika virus to microcephaly we cannot be certain that one causes the other, and further research is urgently needed."

The number of reported cases of newborn babies with microcephaly in Brazil in 2015 has increased twenty-fold compared with previous years. At the same time, Brazil has reported a high number of Zika virus infections, leading to speculation that the two may be linked. Babies born with microcephaly have abnormally small heads, and are at risk of incomplete brain development. Microcephaly has previously been linked to a range of factors including genetic disorders, drug or chemical intoxication, maternal malnutrition and infections with viruses or bacteria that can cross the placental barrier such as herpes, HIV, or some mosquito borne viruses such as chikungunya.

In this study, the team led by Dr de Filippis investigated the case of two women (aged 27 and 35) from Paraiba, a state in northeast Brazil. The two women presented with symptoms of Zika virus infection including fever, muscle pain and a rash during their first trimester of pregnancy. Ultrasounds taken at approximately 22 weeks of pregnancy confirmed the foetuses had microcephaly.

Samples of amniotic fluid were taken at 28 weeks of pregnancy and analysed for potential infections. Both patients tested negative for , and other infections such as HIV, syphilis and herpes. Although the two women's blood and urine samples tested negative for Zika virus, their amniotic fluid tested positive for Zika virus genome and Zika antibodies. The amniotic fluid was analysed using a process called metagenomic analysis. This allows the detection of any microorganism that could be present in the samples, but only Zika virus genome was found. The RNA of the two Zika virus samples was then compared with samples from previous outbreaks, and was found to be genetically related to the strain identified in French Polynesia in 2013.

Writing in a linked Comment, Professor Didier Musso from the Unit of Emerging Infectious Diseases, Institut Louis Malarde in Tahiti, French Polynesia, says: "Even if all these data strongly suggest that Zika virus can cause microcephaly, the number of microcephaly cases related to Zika virus is still unknown. The next step will be to do case-control studies to estimate the potential risk of microcephaly after Zika virus infection during pregnancy, other fetal or neonatal complications, and long-term outcomes for infected symptomatic and asymptomatic neonates."

Explore further: Brazil finds Zika in microcephaly babies' brains

More information: The Lancet Infectious Diseases, www.thelancet.com/journals/lan … (16)00095-5/abstract

Related Stories

Brazil finds Zika in microcephaly babies' brains

February 15, 2016
Brazilian researchers said Monday that the discovery of Zika in the brains of babies with microcephaly adds to growing evidence of a link between the mosquito-transmitted virus and the birth defect.

Zika virus: Five things to know

February 8, 2016
A concise "Five things to know about.... Zika virus infection" article for physicians highlights key points about this newly emerged virus in CMAJ (Canadian Medical Association Journal)

Evidence grows for Zika role in brain damage

February 11, 2016
Evidence piled up Thursday implicating the Zika virus in a surge of brain damaged babies in Latin America, with two reports of the disease found in the neural tissue of affected infants.

Second pregnant woman diagnosed with Zika in Australia

February 12, 2016
A second pregnant woman has been diagnosed with the mosquito-borne Zika virus in Australia, officials said Friday, adding that the disease was acquired overseas and there was no public health risk.

WHO says will know if Zika causes microcephaly in weeks

February 12, 2016
The World Health Organization said Friday that it will know in a matter of weeks whether the Zika virus causes microcephaly and the severe neurological disorder Guillain-Barre syndrome.

Microcephaly cases up 10% in Brazil amid Zika scare

February 17, 2016
Brazil on Wednesday reported a new total of 508 confirmed cases of microcephaly, the serious birth defect suspected of being linked to the Zika virus—a 10 percent jump in less than a week.

Recommended for you

Fresh approach to tuberculosis vaccine offers better protection

January 17, 2018
A unique platform that resulted in a promising HIV vaccine has also led to a new, highly effective vaccine against tuberculosis that is moving toward testing in humans.

Study reveals how MRSA infection compromises lymphatic function

January 17, 2018
Infections of the skin or other soft tissues with the hard-to-treat MRSA (methicillin-resistant Staphylococcus aureus) bacteria appear to permanently compromise the lymphatic system, which is crucial to immune system function. ...

Newly-discovered TB blood signal provides early warning for at-risk patients

January 17, 2018
Tuberculosis can be detected in people with HIV infection via a unique blood signal before symptoms appear, according to a new study by researchers from the Crick, Imperial College London and the University of Cape Town.

New study validates clotting risk factors in chronic kidney disease

January 17, 2018
In late 2017, researchers from Boston University School of Medicine (BUSM) discovered and published (Science Translational Medicine, (9) 417, Nov 2017) a potential treatment target to prevent chronic kidney disease (CKD) ...

New study offers insights on genetic indicators of COPD risk

January 16, 2018
Researchers have discovered that genetic variations in the anatomy of the lungs could serve as indicators to help identify people who have low, but stable, lung function early in life, and those who are particularly at risk ...

Previous influenza virus exposures enhance susceptibility in another influenza pandemic

January 16, 2018
While past exposure to influenza A viruses often builds immunity to similar, and sometimes different, strains of the virus, Canadian researchers are calling for more attention to exceptions to that rule.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.