Zika virus transmitted to people through the bite of an infected Aedes mosquito vector. One of 5 people infected may develop symptoms, and the disease is generally mild. However, clusters of microcephaly and other neurological disorders have been reported in areas recently affected by Zika virus.
Zika virus is a mosquito-borne-flavivirus in the same family as West Nile, dengue and yellow fever. It was first isolated in Uganda in 1947. It caused sporadic human cases in Africa and Southern Asia from the 1950’s until 2007, when an outbreak occurred on Yap Island of Micronesia which later spread to surrounding Pacific Islands in 2013-2014.
In May 2015, the Pan American Health Organization issued an alert regarding the first confirmed Zika virus infection in Brazil. Local transmission of the virus has spread rapidly in the Americas, and outbreaks are currently occurring in many countries. As of February 2, 2016, active Zika virus transmission has been identified in 28 countries, 25 of which are in the Caribbean, North and South America including Puerto Rico and the U.S. Virgin Islands. The CDC has issued a travel alert (Level 2 – Practice Enhanced Precautions) for people traveling to regions and countries where Zika virus transmission is ongoing and suggests that high risk populations may want to delay travel. The CDC recommends that travelers should protect themselves from mosquito bites and pregnant women may want to consider postponing travel where Zika virus transmission is ongoing.
The current known distribution Aedes aegypti in the U.S. includes Alabama, Arizona, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, New Mexico, South Carolina and Texas. Adedes albopictus’ distribution includes Alabama, Arizona, Arkansas, California, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia and West Virginia. Known distribution is estimated and actual distribution may shift quickly due to mosquito movement and weather patterns.
Local transmission of Zika virus has been confirmed in Texas, when it was sexually transmitted from an individual infected with the Zika virus outside the United States to another individual who had not traveled outside the U.S. This method of transmission has only been documented twice prior to the recent transmission in Texas. Typically, the transmission of the Zika virus occurs when humans are bitten by infected female Aedes spp. mosquitoes.
Approximately 80% of Zika infections do not result in symptoms. If symptoms do occur, they include fever, headache, joint pain, conjunctivitis (red eyes), and rash and possible muscle pain. Some travelers to areas with ongoing Zika virus transmission will become infected during the travel but may not become sick until they return home. Severe illness and hospitalization due to Zika infection is uncommon.
There is an increasing body of evidence on the link between Zika virus and microcephaly (congenital condition that causes infants to have below-average head size due to a failure of the brain to grow at a normal rate) and Guillain-Barré syndrome (an autoimmune disease in which the immune system attacks the nerves). Both microcephaly and Guillain-Barré syndrome can be life threatening.
Neurological and auto-immune complications including Guillain-Barré syndrome were reported during recent large outbreaks in French Polynesia in 2013-14 and Brazil in 2015. Between October 2015 and January 2016, more than 4,100 microcephaly cases have been reported in Brazil, 20 times higher than the previous year. A case of infant microcephaly has been reported in Hawaii, the child was born to a mother who had lived in Brazil during her pregnancy. Since many people do not experience symptoms from Zika virus, the rate of pregnant women that have been infected is unknown.
Given an increasing body of evidence and lacking an alternative explanation for these clusters of microcephaly cases and other neurological disorders in areas affected by Zika virus, the World Health Organization (WHO) Emergency Committee declared the current Zika virus epidemic a Public Health Emergency of International Concern on February 1, 2016.
The primary means of transmission of Zika virus is through the bite of an infected Aedes aegypti or Aedes albopictus mosquito. These are the same mosquitoes that transmit dengue, chikungunya and yellow fever.
Zika-infected individuals have sufficient virus in their blood to infect a mosquito for roughly a week following the onset of symptoms. There have been documented cases of transmission during labor, blood transfusion, laboratory exposure and sexual contact, but these are infrequent mechanisms.
There is no treatment or vaccine available for Zika virus. CDC recommends treating the symptoms by resting, drinking fluids, and taking pain medication. There is also no treatment to correct microcephaly. There are special blood treatments for the Guillain-Barré syndrome that helps reverse the temporary paralysis and physical therapy may also needed.
The CDC recommends that all pregnant women consider postponing travel to areas where Zika virus transmission is ongoing. If travel is unavoidable, she should consult with her physician and strictly follow steps to avoid mosquito bites during the trip.
All travelers should protect themselves by preventing mosquito bites. Mosquito prevention strategies include wearing long-sleeved shirts and long pants, using U.S. Environmental Protection Agency (EPA) -registered insect repellents, using permethrin-treated clothing and gear, and staying and sleeping in screened-in or air-conditioned rooms or under mosquito nets. When used as directed on the product label, insect repellents containing DEET, picaridin, and IR3535 are safe for pregnant and breast-feeding women. Unnecessary standing water around homes where mosquitoes can breed should be eliminated such as buckets, flower pots, discarded tires and any additional containers that can collect water.
Mosquito Management and Prevention Through IPM
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Mosquito Bite Prevention Publication
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World Health Organization
Centers for Disease Control and Prevention
The Centers for Disease Control & Prevention (CDC) has issued a travel alert (Level 2 – Practice Enhanced Precautions). The CDC suggests that women who are pregnant (in any trimester) may want to consider postponing travel to any area where Zika virus transmission is ongoing. If travel is unavoidable, it is advised for the individual consult with her physician and strictly follow steps to prevent mosquito bites.
Locations of Ongoing Transmission of Zika Virus as of February 2, 2016
Barbados, Bolivia, Brazil, Colombia, Commonwealth of Puerto Rico, Costa Rica, Curacao, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Nicaragua, Panama, Paraguay, Saint Martin, Suriname, U.S. Virgin Islands, Venezuela
merican Samoa, Samoa