Zika and Microcephaly
In the past several months, Zika, a mosquito born infection, has been spreading rapidly around the world, including on the Atlantic coast of Colombia. Zika is not a new disease. In fact, it was first discovered in the Ugandan forests of Africa in 1947. Zika remained a non-threatening infection relatively confined to certain regions of Africa for over 60 years. In 2007, however, Zika began spreading to other parts of the world including Yap island, French Polynesia and then to Brazil. Today, Zika infection has been reported in many countries. Zika infection was first reported in Colombia in September 2015 and since then, over 72000 cases of Zika infection have been reported in Colombia. Zika infection by itself is generally a short-lasting, relatively mild disease. However, the consequences for the newborns of pregnant women, themselves infected with Zika, are devastating and permanent.
The possible relationship between Zika and birth defects was first observed in Brazil. In October 2015, an increased incidence of microcephaly was found among infants that were born in regions of Brazil where Zika outbreak had occurred several months before.
Microcephaly is a congenital disorder in which the head circumference of the newborn is smaller than usual. The head size of children affected by microcephaly remains smaller than usual as the child grows. Children affected by microcephaly suffer from various conditions including delayed speech and motor function, seizures, balance and coordination problems, and mental retardation.
After the surge of microcephaly in Brazil, several researchers began investigating the relationship between Zika and the increased incidence of microcephaly. The results confirmed the presence of Zika virus and its antibodies within some of the infants` body tissues including blood, cerebrospinal fluids, and brain tissue, showing that Zika can cause microcephaly in the fetuses of pregnant women who become infected with Zika virus sometime during pregnancy. It was also shown that the risk of microcephaly is the highest in women who become infected with Zika in their first trimester or early on during their second trimester of pregnancy.
But the question remained as to why Zika had never caused a microcephaly epidemic in Africa, despite being such a common infection in some areas of that continent. During a recent study, Bewick et al., concluded that the reason Zika does not affect newborns in Africa is due to “natural vaccination.”
Zika has been a very common infection in certain regions of Africa for the past several decades. Most residents of these areas become infected with Zika at an early age and produce a natural immunity against the disease for the rest of their lives. Thus, most young girls build immunity against Zika before their reproductive age preventing the woman from becoming infected during pregnancy, therefore, preventing microcephaly in these countries.
Zika continues to spread around the world. Almost 13000 suspected cases of Zika infection have been reported among pregnant women within Colombia, and, as of April 2016, two-confirmed cases of Zika-induced microcephaly were reported by the ministry of health of Colombia. Zika is transmitted mainly through mosquito bites, maternal-fetal transmission, and occasionally through sexual transmission.
To avoid detrimental congenital defects caused by Zika infection, pregnant women are strongly advised against traveling to regions that are affected by Zika or to take precautions if avoiding these regions is not a possibility. For more general information about Zika and ways to reduce the risks of spreading it, visit our previous Zika article.
Dr. Rasa Nikanjam, BSc. ND