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Before the Zika virus outbreak, which appears to be associated with serious birth defects in babies in Brazil, there was rubella, also known as German measles, which terrified the pregnant women of my mother's generation.
In the 1964-1965 rubella pandemic, an estimated 50,000 pregnant women in the United States were exposed to rubella in pregnancy, resulting in miscarriages, stillbirths, and 20,000 babies born with congenital rubella syndrome, which caused blindness, deafness, brain and heart damage. At the height of the pandemic, an estimated 1 of every 100 babies born in Philadelphia was afflicted.
A vaccine for rubella was introduced in the 1970s, so parents no longer have to live in fear. But I still remember David, my first-grade friend Kathy's little brother. Kathy's mom came down with rubella while pregnant and David was born mentally retarded. He never learned to speak, but would flap his hands and burble excitedly in the doorway when Kathy and I were playing Barbies, then flit away. As an adult, I met Kathy again. She told me David died and her face crumpled.
So far the link between Zika virus, brain damage and microcephaly is suspected, not proven. But because Zika appears to be one of the few viruses that can be transmitted from a pregnant woman to a fetus, scientists are looking at what we already know about other viruses that pass the placental barrier as well, including rubella and cytomegalovirus (CMV), to see if it can be used to help combat Zika.
"That is why I'm interested in joining the effort in finding out if Zika is truly the cause of these effects," says Dr. Sallie Permar, a pediatric infectious disease specialist at the Duke Human Vaccine Institute who studies these viruses.
I talked with Permar about what's known about rubella, Zika and the other viruses. The conversation has been edited for length and clarity.
How did scientists figure out that rubella was causing miscarriages and birth defects?
Rubella virus was early on recognized to cause fetal disease. Often there were outbreaks of rubella virus in the summer months. The waves of rubella epidemics were followed by the birth of children with long-term neurological deficits.
I can imagine it was very terrifying to be pregnant when it spiked.
How do the viruses pass from the mother to the developing fetus?
Exactly how these viruses cross the maternal-fetal barrier is still not yet understood. There are very few viruses that are known to cause congenital infections. Although we think of the immune system as usually blocking viruses, there have been some hypotheses that the mother's antibody response may actually work in opposite ways; that if the antibody does not fully neutralize the virus it may actually help in carrying the virus across the placental barrier.
Do these viruses pass from mother to child in the same way?
They have similarities and they have differences. The modes of transmission of HIV and cytomegalovirus are similar so that they can be passed to the fetus during pregnancy, during delivery, when the baby is exposed to the virus in the birth canal or through breast milk.
One thing that is very different between HIV and CMV, we know that any time an infant gets HIV, that's a pathogenic infection. If a fetus becomes infected with CMV during pregnancy, it can lead to neurologic deficits. However, if a baby gets infected during delivery or after birth via breast milk feeding, that is usually totally asymptomatic.
Does it matter when a woman gets infected?
We often don't know when congenital infections are transmitted. Likely when the mother is infected could affect transmission, but it is going to be different with every pathogen. Some neonatal pathogens hit hardest around delivery.
Why is everyone routinely given the vaccine for rubella?
In adults and children, rubella causes fever, maybe some rash; it really was the sort of a childhood illness that was mild and would go away on its own. So the vaccine was not introduced to stop the mild febrile illness but to interrupt the congenital transmission. It's an altruistic vaccine. You are protecting the mother to protect the fetus.
What people say is when the rubella vaccine came out, schools for the deaf and blind had to close because there weren't enough children to attend them. It really is a story of such success. We've sort of forgotten why vaccines are so important.
Wendy Wolfson is a science writer in Orange County, Calif.
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