The Centers for Disease Control and Prevention have issued travel warnings aimed at pregnant women and women trying to become pregnant for a large number of countries in Central and South America due to the spread of Zika viral illnesses. Brazilian authorities have reported a large increase in a rare birth defect called microcephaly which may be related to Zika infections in expecting women.
CDC has issued a travel alert (Level 2-Practice Enhanced Precautions) for people traveling to regions and certain countries where Zika virus transmission is ongoing: Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Suriname, and Venezuela.
Zika is a viral illness spread by infected mosquitoes. It has been found in Central Africa, South Asia, Southeast Asia and the Pacific Islands. It appeared for the first time in the Americas, in northeastern Brazil, in the fall of 2015.
The illness is spread by two mosquito species, both widespread in the Western Hemisphere. Aedes albopictus (Asian Tiger mosquito) and Aedes aegypti (Yellow Fever mosquito) are the two vectors believed to be involved in this outbreak. Both mosquitoes also can transmit the four dengue viruses, the chikungunya virus and (obviously) the yellow fever virus.
The latest report from Brazil shows that they have diagnosed 3,530 cases of microcephaly through the beginning of Jan. 2016. Nearly all are reported in the country’s Northeastern Region, and in that region, the states of Pernambuco, Paraiba and Bahia account for over 2/3 of the total.
In an interview Jan, 13, Dr. Peter Hotez, Director of the Texas Children’s Hospital Center for Vaccine Development and Founding Dean of the National School of Tropical Medicine at Baylor College of Medicine, told me that this is the largest Zika outbreak seen to date. While there is little data on the appearance of microcephaly after Zika outbreaks in other parts of the world, he suggested that there may be two reasons for the lack of data. Prior outbreaks have been much smaller, producing less of any sequelae. He also suggested the possibility that the virus may have mutated and become more neurotropic.
Not a great deal of study has been done on the Zika virus. The CDC states that the symptoms of a Zika infection are:
- About 1 in 5 people infected with Zika virus become ill (i.e., develop Zika).
- The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache.
- The illness is usually mild with symptoms lasting for several days to a week.
- Severe disease requiring hospitalization is uncommon. Deaths are rare.
“Microcephaly is a medical condition in which the circumference of the head is smaller than normal because the brain has not developed properly or has stopped growing,” according to the National Institute of Neurological Disorders and Stroke.
Babies may also be born with microcephaly if, during pregnancy, their mother abused drugs or alcohol, became infected with a cytomegalovirus, rubella (German measles), or varicella (chicken pox) virus, was exposed to certain toxic chemicals, or had untreated phenylketonuria (PKU).
Dr. Hotez knows of no arbovirus that produces this type of birth defect in a fetus. He noted that a rubella outbreak in Philadelphia in 1964-1965resulted in congenital rubella syndrome (CRS) in one percent of all births.
Northeastern Brazil was the site of an outbreak of measles in 2013-2014. In one study, 181 of 252 measles patients had received one or fewer doses of MMR vaccine. A quarter of the cases were in patients with an unknown vaccination status.
The appearance of measles and the preponderance of illnesses in the poorly vaccinated points to the potential for outbreaks of the other illnesses covered by the MMR vaccine, mumps and rubella. The CDC states “About half of the people who get rubella do not have symptoms.”
The prudent course of action is to warn women about the potential dangers of a Zika infection. Further investigation is ongoing, in Brazil, the United States and worldwide. For your consideration, I offer:
- Northeastern Brazil has recently been shown to be undervaccinated for measles, and thus rubella.
- About half of those contracting rubella may not know that they have the illness.
- For those who experience symptoms of rubella, they are similar to those produced by a Zika infection.
- There may be a correlation between Zika infections and microcephaly but no causation has been demonstrated at this point.