Zika Virus, Linked To Microcephaly And Transmitted By Mosquito, Spreading In Americas

A mosquito-borne virus, Zika, is spreading throughout the Americas. Although not usually life-threatening, Zika has been linked to serious birth defects, including an epidemic of microcephaly in Brazil, and has now been identified in 10 countries, according to LiveScience.

Brazil, Chile, Colombia, El Salvador, Guatemala, Mexico, Paraguay, Suriname, Venezuela, and most recently Panama all have instances of the virus.

In Brazil, 1,761 cases of microcephaly have been reported, which are believed to be linked to the spread of Zika, according to Reuters. Microcephaly is a birth defect that causes underdevelopment of an infant’s brain and head, severely limiting cognitive and muscle function in sufferers. As of December 5, 19 children in Brazil have died from the disorder, according to the World Health Organization.

The outbreak of microcephaly has actually led Brazil’s Ministry of Health to revise the definition of the disease, announcing a change on December 7 that it now included babies with a head circumference of less than 32 centimeters. The previous definition of microcephaly was 33 centimeters.

Zika, which is also found in Africa and Southeast Asia, only began spreading via native South and Central American mosquitoes recently. The first known case occurred in Chile in February 2014. Since then, Zika incidents have been spreading quickly.

Though the link between Zika and microcephaly has not been conclusively established, the timing of the two conditions’ spread is very close. According to Medscape, in 2010 there were 5.7 cases of microcephaly per 100,000 births. Following the outbreak of Zika, that number has increased 20-fold to nearly 100 in every 100,000.

On December 1, the Pan American Health Organization issued a statement to its member states urging a proactive fight against the spread of Zika through mosquito control strategies. The PAHO also recommended is member states “establish and maintain the capacity to detect and confirm Zika virus cases, prepare healthcare facilities for the possible increase in demand at all healthcare levels and specialized care for neurological syndromes, and to strengthen antenatal care.”

Prior to its American spread, Zika was found mostly in Africa and Southeast Asia. Travelers could carry it back to their home country, but without native mosquito vectors, it didn’t spread. In 2007, the earliest outbreak of Zika outside its previously known range occurred in Micronesia, according to the journal Emerging Infectious Diseases.

Aside from the birth defects, symptoms of Zika sufferers can include, depending on the region and particular strain of the disease, rash, joint pain, fever, back pain, conjunctivitis, vomiting, diarrhea, and headaches. Zika is in the same family of diseases as yellow fever, dengue, West Nile, and Japanese encephalitis viruses.

The culprit behind Zika, according to the Centers for Disease Control, is the Aedes mosquito. This species is also known to spread dengue and chikungunya. There are no known, natively transferred instances of Zika in the United States, but the Aedes mosquito has a range that covers much of the southeastern United States.

In the Emerging Infectious Diseases article, published in 2009, author Edward Hayes notes, “Fortunately, [Zika] to date has been mild and self-limited, but before West Nile virus caused large outbreaks of neuroinvasive disease in Romania and in North America, it was also considered to be a relatively innocuous pathogen.”

At the time of the publication of Hayes’s paper, Zika hadn’t yet been identified in the Americas. With the rash of microcephaly plaguing Brazil and health experts’ suspicion that the birth defect is related to the spread of Zika, it appears Zika may have more dangerous surprises in store than the relatively mild symptoms experienced by adult sufferers.

How exactly the birth defect is passed onto a child, or even if there is a direct link, has yet to be established. Zika itself is only rarely transmitted from mother to offspring, and only in instances when the mother is infected near the time of birth, according to the CDC.

Still, health experts have not recommended any travel or trade restrictions as a result of the Zika outbreak, according to Reuters. The World Health Organization recommends the usual precautions, most notably avoiding mosquitoes. Currently, there are no medicines or vaccines to treat or prevent Zika.

[Photo by Muhammad Mahdi Karim/Wikipedia]