An outbreak of a little known virus called the Zika virus has caused women infected during pregnancy to give birth to infants with microcephaly, a condition marked by an abnormally small head, mental retardation, and growth and developmental abnormalities.
The outbreak is predominantly occurring in Brazil, where the Brazilian Health Ministry recently reported 3,530 cases of microcephaly and 46 infant deaths possibly linked to the virus. In 2015 at least 2,782 cases of microcephaly were reported compared to 147 in 2014. The number of cases is increasing daily, and the peak mosquito season is in April, bringing fears that the pandemic is not even near peak levels. The government has recommended that women in areas where the mosquitos are prevalent delay conception and that pregnant women take all possible precautions to avoid mosquito bites.
The Zika virus is a relative of the dengue, yellow fever, and West Nile virus and is transmitted via mosquitos of the Aedes species. It was first discovered in the Zika forest in Uganda in 1947 and is common in Africa and Asia. However, it did not spread to the Western Hemisphere in Brazil until 2015. Researchers are uncertain as to how the virus jumped to Brazil, but speculate Brazilian mosquitos of the Aedes species acquired the virus by biting infected travelers from Africa. These mosquitos then transmit the virus to others when they feed.
Tests were recently performed by the U.S. Center for Disease Control on tissue sent from Brazil from two pregnancies which resulted in miscarriage and from two infants with microcephaly who died shortly after birth. Genetic sequence analysis confirmed that the strain of the Zika virus in the fetal tissue and in the newborn brain tissue was the same as the Zika virus strain circulating in Brazil.
As a result, the CDC issued a travel advisory recommending that pregnant women at any stage of pregnancy avoid travel to Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, and the Commonwealth of Puerto Rico.
Infection with the virus causes symptoms in only 20% of those infected. The symptoms include fever, rash, joint pain, and red eyes. There currently is no widely available test specifically for Zika infection. There is also no vaccine available.
There has only been one reported U.S. case of Zika induced microcephaly. The mother lived in Brazil while pregnant and then gave birth in Hawaii. There have been, however, multiple cases of Zika diagnosed in the U.S. in travelers who visited affected countries and in Puerto Rico. While the Aedes mosquito is found in parts of the U.S., experts anticipate that U.S. Zika infections, like those of dengue and yellow fever, will be limited.
Microcephaly is not treatable. Infants with microcephaly frequently have other associated abnormalities in growth, behavior and development. Microcephaly may occur as an isolated abnormality, or may be accompanied by other birth defects. It may also be acquired after birth due to malnutrition, infection, or trauma. It is considered a rare condition, occurring in 1 in 6200 to 8500 births. The most common causes of microcephaly have been genetic disorders (Down’s syndrome, Cri du Chat syndrome, Trisomy 13, Trisomy 18), maternal alcoholism or drug abuse, maternal infections (rubella, toxoplasmosis, cytomegalovirus), maternal malnutrition, mercury poisoning, maternal diabetes, and uncontrolled maternal PKU. The Zika virus must now be added to the top of the list.