Infections and Microcephaly

What other viruses can cause babies to be born with smaller heads?

What’s Microcephaly again?

Microcephaly is a condition where a baby has a head smaller than expected – smaller for age, gender, size. The precise definitions often changes. Brazil is using the head circumference cut off to be 32cm, but was using 33cm previously. (This means a tape measure wrapped around a baby's head would not reach 32cm. This can be 2 standard deviations below the norm or 3. It can be the 3% of the population that have the smallest heads).

Microcephaly is associated with brain underdevelopment. It can be severe with significant developmental delays, as well as seizures, and other difficulties. Others may not have these limitations and complete their schooling like their peers, depending on the severity of the presentation.

Are there viruses that cause babies to have microcephaly?

Zika has been grabbing headlines. Its explosive spread in Brazil and elsewhere in Latin America was a pain, but only caused a mild illness in most. However, it soon became apparent that there were more cases of microcephaly occurring. This has been linked, potentially, to Zika, but there is conclusive proof that Zika in pregnancy causes microcephaly.

Are there other viruses that cause microcephaly?


Varicella The virus that causes chickenpox can also be pretty nasty in pregnancy. Before vaccination existed, very few children made it to adulthood without being infected.

As a result, very few women were at risk of getting chickenpox while they were pregnant. Most had been infected and had become immune before they became pregnant. In those rare cases where a mother developed varicella during pregnancy, there were multiple risks to the baby. One of these was microcephaly.

Chickenpox can also be a serious illness to the mother as well.

Rubella The virus that is now eliminated in the Western Hemisphere used to cause birth defects if mothers were infected during pregnancy. One of these birth defects was microcephaly. These birth defects - Congenital Rubella Syndrome - was much of the reason for focusing on elimination. Rubella vaccination has been pretty important, preventing a lot of babies and their families from facing these problems.

Cytomegalovirus (CMV) The virus, which is quite common, leads to a mild mono-like illness in the mother, but can have substantial effects on the infant. An infection carries a 30-40% risk of transmission to the fetus; about 1 in 4 to 1 in 5 infected fetuses will show signs of the infection after birth. This can lead to a number of impairments – such as hearing loss, as well as visual and development abnormalities. It can also lead to microcephaly.

Toxoplasmosis This  parasitic infection can lead to microcephaly as well. It can also lead to other signs – rash, yellowed eyes or skin (jaundice), and calcifications in the brain, as well as eye problems and water build up in the brain (hydrocephalus).

HIV Pregnancies in HIV+ mothers can be quite healthy with good medical care. In those who do not have access to or cannot access HIV medications, there can risks to the baby. Of these risks, microcephaly has been identified occasionally.

There are a number of other causes of microcephaly – such as alcohol use and certain genes or trisomies (when a baby has 3 rather than 2 copies of chromosome 13 or 18 - and also Down Syndrome with chromosome 21).

Women who are ill should seek medical attention. It's very important during pregnancy to seek medical attention if there are any concerns.

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