The Surprising Virus That Could Be Causing Autism

New findings published in Science Magazine show a definitive link between herpes simplex virus type 2 (HSV-2), a sexually transmitted disease, and an increased risk of having a child with autism:

Herpes simplex virus type 2 (HSV-2), the primary cause of the blistering genital disease that infects roughly one in five U.S. women of childbearing age, may play a role in autism, according to a new study. Active infection with the virus in early pregnancy doubles the chance that a male fetus will develop autism spectrum disorder (ASD) early in life, researchers have found in studying one large Norwegian population. The finding does not mean that all pregnant women with an active HSV-2 infection will give birth to autistic children, but that—in a subset of women thought to be genetically predisposed—the infection may be one of an unknown number of triggers for the condition.

According to researchers, it is possible that a percentage of women with HSV-2 are “genetically predisposed to develop intense immune responses” to the virus. In this case, the antibodies and inflammatory molecules generated by this intense immune response cross the placenta and damage the developing baby’s brain. In other words, it isn’t the herpes virus itself that is damaging fetal brain tissue, but a mother’s unique and extreme response to the herpes virus.

“We’re not saying that HSV-2 is responsible for infecting the [fetal] brain and causing autism,” stresses senior author Ian Lipkin, an infectious disease expert and epidemiologist at Columbia. Indeed, fetal infection with HSV-2 is so serious that it frequently leads to miscarriages or stillbirths. Rather, Lipkin suspects that HSV-2 is just one among many environmental insults that, when they arrive at a vulnerable point in fetal development in women predisposed to damaging reactions, may trigger ASD in the fetus. That idea comports with a body of previous work, like this Swedish study that found that the hospitalization of a woman for any kind of infection during pregnancy increased the risk of the baby developing ASD by 30%.

It is important to note that there is no cure for herpes. Once a person has been infected they carry the virus with them for life. Sexual partners can transmit the disease even if blisters are not present at the time of sexual contact. And while drugs exist to treat the blistering symptoms of herpes, no drug exists to address a pregnant woman’s extreme immune response to the virus.

Given that herpes outbreaks are often triggered by fatigue as well as physical or emotional stress, it isn’t surprising that women who are pregnant and infected with the herpes virus would experience outbreaks as a result of the pregnancy. Women with herpes face additional risks to their pregnancies. According to the CDC, these risks include an increase chance of miscarriage or premature birth, as well as the chance of passing a potentially deadly infection known as neonatal herpes to the unborn child. If herpes symptoms are detected at birth a C-section will be performed to deliver the baby safely.