Microcephaly, Zika, and Travel Warnings for Pregnant Women

What Do Zika and Microcephaly Mean?


It sounds like something out of a sci-fi movie. A virus - a mild one at that - might lead babies to be born with small heads. Not something pregnant women want to worry about. Pregnancy alone causes enough worries. Unfortunately, there are thousands of women who might be worried. The virus blamed - Zika - has been spreading in Brazil over the last year and is now in other parts of Latin America and the Caribbean.

What is Microcephaly?

Microcephaly (my-cro-SEF-uh-lee) is where a baby's head is smaller than expected. The word refers simply to a small (micro in Latin) and head (-cephaly in Greek). 

Microcephaly is a development abnormality where a head is too small relative to the body and compared to others of the same age. This can be noticed at birth. The small head often means that the brain is not just small but it has developed abnormally. This can mean neurologic delays for affected children. The specific delays will depend on the severity and specifics of the abnormal development.

There is a wide range of sizes of newborn baby heads. Some are too big and some are too small, which may point to different problems that need to be addressed. Microcephaly is defined as a head  much smaller than average. Babies heads are usually measured soon after birth and at doctor's visits, where it can be diagnosed.

It can also be diagnosed on an ultrasound during pregnancy, which may also show other abnormalities. (This may be defined as 2 standard deviations below the mean (or average) - or it may be 3 standard deviations below). 

What does microcephaly mean for babies?

It is a lifelong condition. There is no treatment to reverse it if diagnosed.

The underlying cause may need to be treated.

It can be associated with developmental delays (slow to speak, sit, stand or walk), intellectual difficulties (problems learning or functioning in daily life), seizures, problems seeing or hearing, problems eating and swallowing, and difficulty walking or balancing. Developmental services with early intervention and other support and medical services may help children. Different cases have different developmental courses. Please see the CDC site for more information.

What causes microcephaly?

There are many possible causes of microcephaly

Microcephaly is uncommon. It is often not diagnosed everywhere. It may not be looked for or it may not be recorded everywhere.The diagnosis depends on what criteria is used. There is variation in the definition of microcephaly with different head sizes used.

Microcephaly can be primary - where the brain does not develop from the start, which is generally genetic. This can be due to having a particular gene. In some cases, microcephaly can be due to having one more chromosome than most people.

Microcephaly can also be secondary - where brain development begins normally but is halted or tissue is damaged.

Cases not due to genes can be due to viruses - like CMV, Chickenpox (Varicella) and Rubella (German Measles). It can be caused by other infections like Toxoplasmosis. Microcephaly can be connected to exposure in utero to alcohol and even malnutrition or lead or mercury exposure. It can be due to a traumatic injury. It may also be connected to diseases in the mother, like Phenylketonuria (PKU). Sometimes it seems like an exposure is the cause but it likely is not.

What does this have to do with Zika?

The CDC has provided guidance that pregnant women postpone travel to areas with Zika because of concern that infection of the mother at any stage of pregnancy may increase the risk of microcephaly. The CDC also recommended those planning a pregnancy to discuss with their doctor if considering travel to affected areas. 

What made us originally think Zika caused microcephaly?

Zika has been known for years, but it's role in the development of babies was never recognized. It may have been in areas where it was so common that most were infected as children, well before becoming pregnant. It may have been rare enough, spreading mostly between monkeys and mosquitoes, that few pregnant women were infected. Or it may have been that so few babies were born in facilities that tracked microcephaly - and Zika did not occur as a sudden epidemic - that the relationship between a mild (or non-existent) symptoms in pregnancy was not correlated with occasional birth defects.

This all changed when Zika arrived and gathered momentum in the Western Hemisphere. No one was immune. The population of mosquitoes and people were vulnerable. The virus spread, epidemically. 

a. In Brazil, 2 miscarriages and 2 babies born with microcephaly were shown to have the Zika virus present, mothers reported having had Zika symptoms, and the 2 babies born were shown to have Zika present in their underdeveloped brains.

b. A baby born in Hawaii was born with microcephaly and was found to have Zika after the mother had symptoms during pregnancy when she lived in Brazil early in pregnancy.

c. Brazil recognized many more cases than it usually saw of microcephaly. The Zika virus first arrived in May 2015, from October 2015 to the beginning January 2016, over 3500 cases of microcephaly were detected. Some cases were particularly severe; some died. Even if this interest in microcephaly led to more recognition of cases, which otherwise would have been under-reported, this is a notably higher rate. This has reached over 10x higher than normal.

This also doesn't seem to be simply a case of Brazil suddenly diagnosing microcephaly. The US usually diagnoses microcephaly in 2-12 babies per 10,000 live births. This would about 200 to 1200 cases in 3 months in the US, which sees more births. Brazil has fewer babies born (Brazil has roughly 3/4 the number of births. Brazil has less than 2/3 the population of the US (200 million vs 318 million) and only a slightly higher birth rate (15/1000 compared with 13/1000)).

d. The cases of microcephaly were most common in areas hardest hit by Zika - near Bahia in the Northeast of Brazil.

e. We know that other viruses can lead to microcephaly, like varicella and CMV.

f. Ultrasound in Brazil showed microcephaly in two fetuses along with specific signs (like calcifications) similar to other viral brain infections. Both pregnant mothers reported having had Zika-like symptoms (but were now negative); amniocentesis documented Zika in the amniotic fluid, ie. in utero infections.

Given these concerns, the Brazilian Ministry of Health, the US CDC, and many others are worried about the effect this infection, otherwise mild, may have on infants.

Why are we just learning this now about Zika?

Zika is new to the Western Hemisphere, but it is not new to the world. It has been found in Africa and more recently Asia and the Pacific Islands. It has been recognized for over 50 years. The virus though is often not diagnosed in clinics. It's likely if there were an association, it might not have been found. There also would not have been as many pregnant women getting infected and so an 'outbreak of microcephaly' would not be present, which would have facilitated the correlation. In clinics with fewer resources, records may not be kept on details like microcephaly, even if recognized. Babies - and even fetuses - with severe microcephaly may also not survive as long, especially if resources are more limited.

Also, in an area where the virus was common, girls would get bit by a mosquito and infected well before they were old enough to become pregnant, and therefore avoid this problem. This is seen with Chickenpox, which usually affected children and not pregnant women, in countries like the US before vaccination was available.

It is also possible that the sudden emergence may affect, even amplify, viral load dynamics.

How does one catch Zika?

Zika comes from mosquito bites. In particular, from bites of a mosquito that has bitten someone who is infected. The mosquitoes that transmit Zika are Aedes aegypti and Aedes albopictus, which can also carry Dengue, Chikungunya, and Yellow Fever.

There is also the chance that a partner's travel also matters for pregnant women. If a woman avoids travel or returns from a place with Zika, there is the possibility that she could face risk if her partner contracts Zika and returns to see her. There was a case in the US where a traveler returned to Coloado with Zika and his wife was infected, though she didn't travel and had no other exposure thought to have been able to transmit it. Zika virus has been shown in sperm sample infected even when not found in the man's blood.

Blood transfusions may also transmit Zika, which can matter for some anemic, pregnant women.

Where is Zika?

Brazil, Antigua, Aruba, Barbuda, Barbados, Bolivia, Colombia, Costa Rica, Cuba, Curacao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Jamaica, Martinique, Mexico, Nicaragua, Panama, Paraguay, Saint Martin, Suriname, Trinidad and Tobago, Turks & Caicos, Venezuela, Puerto Rico. It has also been seen in Cape Verde off West Africa, Guinea-Bissau in West Africa, and American Samoa, Samoa, Tonga in the South Pacific.

Is there Zika in the US?

Travelers have returned with Zika over the years. No transmission has ever been recorded by mosquito bite in the US (There is the potential that years ago a case in Colorado was due to sexual transmission from an infected man). Recently some returned to Texas, Illinois, New York, California, and other states with a Zika virus infection.

One more thing, is Microcephaly just a small head?

Microcephaly is often associated with other findings. There can be calcifications in the brain (clumps of calcium that don't belong in the brain); the brain mass can be very small; the ventricles can be large (which is where the cerebrospinal fluid that flows around the brain passes through).

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