Scientists working on unraveling the mystery of the Zika virus and the epidemic in Latin America that has resulted the birth of thousands of babies with birth defects, but surprisingly some sets of twins that had differing results. The researchers are hoping to learn more about the virus and its effect on genes, particularly why at least five pregnant women who were carrying twins when they contracted Zika had one normal baby and one with microcephaly, an unusually small head indicating abnormal brain development.
Cases of newborn twins, where one had microcephaly and the other did not, caught the attention of medical professionals in 2015. The sets of twin infants show the devastating difference at birth and beyond between the development of a child born healthy and those with microcephaly. The mystery the researchers are looking into is why the sick mother only passed on the Zika-caused defect to one of her embryos.
A team from Sao Paulo University in Brazil is now studying five sets of twins to find clues as to the nature of the Zika virus, why it is causing the microcephaly and other defects, and how the two embryos thrived differently.
Among the questions they hope to answer is “How was it that one of the twins was not affected. Was there a genetic difference that protected one? Did one have a different genome that reacted to the infection or not?”
Twin studies are fairly common in the annals of medical research. Research has been done on why one twin versus the other develops diabetes, arthritis, Alzheimer’s, and other conditions. They have been done on dietary choices, developmental differences, and such, all of which indicate divergences growing up. But, these children were exposed to the same Zika virus, diet, environment, etc., in utero – with vastly dissimilar results.
In the last year, scientists have found evidence of Zika in amniotic fluid, the placenta and brain tissue in fetuses of women who had the illness while pregnant. One theory the researchers in Sao Paulo are looking into is whether the placenta of one twin was permeable to Zika, while the other was not. Another possibility under consideration is that the virus penetrated both placentas but that one baby was resistant to the virus, while the other was not. Another thing being looked at is whether or not there are genetic differences that protect some children.
The Zika epidemic running rampant since Spring 2015 is unprecedented. The disease, first discovered in the 1940s, was always assumed to be mild and flulike. However, for thousands of women who thought they had a cold, flu or allergic rash during their pregnancy, giving birth to a baby with microcephaly or other defects was the first indication that something more was involved, which blood tests later proved. It has only been months since public health officials confirmed that contracting the disease while pregnant is a cause of microcephaly and other brain abnormalities.
Now, pregnant women throughout the Latin America, the Caribbean and other countries are acutely aware of the threat and appropriately worried. The outbreak, and its impact on pregnant women, has cast a shadow over the upcoming summer Olympics in Rio de Janeiro on August and forced many to change travel plans.
In the interim, public health officials and researchers continue to develop more information about Zika and its aftermath. If there has been any good news, it has been the determination that not every pregnant women who catches the illness will absolutely have a child with birth defects, as the cases of the twins clearly illustrate. Hopefully, studying the sets of twins will aid in unraveling more of the mystery of why Zika is affecting babies, but not all.
Written and Edited by Dyanne Weiss
CNN: One Zika twin has microcephaly; the other doesn’t. But why?
Scientific American: Brazil Scientists Seek to Unravel Mystery of Zika Twins
Fox News: Zika twins with only one microcephalic baby offering clues to doctors in Brazil
Photo courtesy of Donnie Ray Jones’ Flickr Page – Creative Commons license