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Zika Virus: Important Questions Answered

Medically reviewed on Nov 21, 2016 by C. Fookes, BPharm

The Lowdown - What is Zika?

Zika is viral infection caused by the Zika virus. This virus is more commonly spread through the bite of an infected Aedes species mosquito.

The first reported case of Zika in humans occurred in the 1960s in Nigeria. Outbreaks have previously been reported in tropical Africa, Southeast Asia, and the Pacific Islands. Researchers have suggested the Zika virus responsible for the current widespread outbreak stemmed from the Pacific Islands, possibly somewhere between May and December 2013, more than a year before it was first reported in Brazil.

From there, the disease spread rapidly to include most of South and Central America, the Caribbean, Puerto Rico, various Pacific Islands and Singapore.

Florida and Texas were the only U.S. states to report locally acquired infection, although numerous travel-related cases were reported in other states.

How Is Zika Spread?

Most Zika infections are transmitted via mosquito bites particularly from the day-time active Aedes species of mosquito. The mosquito bites an already infected human, then bites an uninfected person, transmitting the virus to them. Monkeys can also harbor the virus. The Aedes species of mosquito is also responsible for the transmission of other viral illnesses, such as Dengue fever and Chikungunya.

Luckily, the more common and globally prevalent Culex mosquito does not appear capable of spreading the virus.

Zika can also be spread sexually through semen and possibly oral sex; and via infected blood transfusions. Pregnant women infected with the virus can pass it onto their unborn child via the placenta. It may also be possible to catch the virus through sweat or tears. Spread through saliva or urine has not yet been confirmed. It does appear that the Zika virus can survive on hard surfaces, such as bench tops and door handles, for hours; however, common household disinfectants are highly effective at killing Zika.

What Are The Symptoms?

Four out of five people infected with Zika experience no symptoms, or symptoms that are barely noticeable. One out of five people develop "Zika Fever", symptoms of which include a low-grade fever, headache, a facial rash that rapidly spreads over the whole body, joint and muscle pain, and conjunctivitis (red eyes). Abdominal pain, tiredness, nausea or vomiting may also be reported. Symptoms usually arise within 10 days of a bite from an infected mosquito and recovery usually takes a week. Hospitalization because of the disease is uncommon.

The biggest concern with Zika virus infection is that outbreaks in Brazil have been associated with a twenty-times higher rate of babies born with microcephaly (small head, incomplete brain development) and intracranial calcifications (calcium deposits in the brain). In addition, an increase in the number of cases of Guillain-Barré syndrome - an autoimmune nerve disorder that causes rapid-onset of muscle weakness and paralysis - have also been reported.

Zika can also cause uveitis, an inflammation of the eye, which if left untreated could cause cataracts and increased eye pressure. A case of sensory polyneuropathy tied to Zika infection has also been reported in an elderly man.

How Is Zika Diagnosed?

Blood tests can help confirm Zika infection; however, few laboratories offer Zika testing. Rapid virological PCR tests used 3-5 days after the onset of symptoms can help distinguish Zika from other viral infections. Other tests look for the presence of antibodies. During a widespread outbreak, most people will be diagnosed clinically, based on their symptoms and recent history (ie, known Zika outbreak in their region or recent travel to areas where the virus is circulating).

In Brazil, diagnosis of Zika was initially challenging because of the similar way the disease presents to Dengue fever and Chikungunya. Looking back, an outbreak of disease attributed to Dengue fever in Brazil in early 2015 may have actually included a number of Zika virus infections, meaning the disease was probably rampant earlier than previously thought.

What Countries Have Reported Cases Of Zika?

Locally transmitted Zika virus has been reported in over 50 countries, including Cape Verde, the Caribbean including Jamaica, Central and South America, Mexico, Singapore and the Pacific Islands (American Samoa, Samoa, and Tonga).

Worldwide, almost every country has reported Zika in returning travelers, including pregnant women.

In the United States, several locally transmitted Zika cases were reported around Miami. At least twenty-six cases of birth defects and five deaths in newborns attributable to Zika have been reported to the CDC. Authorities encouraged all pregnant women who had visited Miami-Dade County in Florida to get tested for Zika infection.

Why An Outbreak Now?

Although small and relatively minor outbreaks of Zika have previously been reported in tropical regions, the current outbreak in Brazil is unprecedented. Why?

Global trade and travel has contributed to the explosive spread of the Aedes species of mosquito, such that it is now present in every continent, including North America. As a result of climate change the world is getting warmer and wetter - the perfect breeding ground for all types of mosquitoes. Statistics already show that Dengue fever infections rose 30-fold from the 1960s to 2013. International travel and the fact that almost 80% of people carrying the virus are asymptomatic means the virus can be easily spread by people who don't even know they have it. In addition, the disease has been relatively uncommon up until now, meaning most populations have no immunity against it.

The World Health Organization (WHO) has warned that the virus is likely to spread throughout the majority of the Americas by the end of the year. WHO has also declared that Zika-virus associated microcephaly and Guillain-Barré syndrome are a public health emergency of international concern.

Treatment For Zika

Unfortunately, there is no specific treatment available for Zika, although scientists have identified a gene pathway vital for Zika transmission that may represent a potential pathway for treatment, and three drugs have been identified that may potentially slow the effects of the virus in pregnant women.

Most people recover from the illness within a week; however, uncommonly some people develop Guillain-Barré syndrome, uveitis, and some babies born to women infected with Zika are born with microcephaly, or other birth defects, such as hearing loss.

Supportive therapy (such as fluids, acetaminophen, rest) may make people more comfortable. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are not recommended until Dengue Fever has been ruled out to reduce the risk of bleeding.

People with Zika virus infection should be careful to avoid mosquito bites to reduce spreading the disease to others, and no traveler should donate blood within 28 days of traveling to a Zika-infected area.

A vaccine against Zika is under development and in August, early clinical trials were launched to assess its safety in humans. The Obama administration has requested $1.8 billion in funding to help combat the threat of the virus.

How Can I Avoid Getting Zika?

The same precautions recommended to protect against Dengue and Chikungunya also protect against Zika.

Eliminating or controlling mosquito breeding grounds is the most effective way to control the virus. Any container or natural depression that collects water - even as little as a teaspoonful - can become a breeding ground for mosquitoes, including water tanks, old tires, discarded tin cans, gutters and flat roofs. Water receptacles for drinking should be covered with a lid and other stagnant areas sprayed. Introduce larvivorous fish, such as guppies, to ornamental water features as these eat mosquito larvae.

Protect yourself from mosquito bites, even during the day by wearing long sleeves and pants, installing insect screens to windows and doors, sleeping under mosquito nets and using an insect repellent such as DEET or picaridin.

Advice Pertinent To Pregnant Women

If you have a trip planned to an area already infected (or likely to soon become infected) with the Zika virus, experts say to seriously consider postponing your trip until after you have the baby. This is in line with CDC recommendations. The first two trimesters of pregnancy seem to be the most dangerous time for the unborn baby to be exposed to the virus; however, Zika can still cause lesions in the brains of unborn babies right up until birth. No matter which trimester you are in, it is best to save your trip for another time.

If travel to a Zika-infected country is unavoidable, then take the utmost precautions to protect yourself from mosquito bites. Since the virus is often symptomless and microcephaly may be difficult to detect on ultrasound, you may not realize you have been exposed to the virus until after your baby is born.

El Salvador has advised all women in the country not to get pregnant until 2018. Colombia and Equador have issued similar advice stating that women should avoid getting pregnant until the dangers of the virus are better understood. United Nations' officials advise all couples living in Zika infected areas to delay pregnancy.

If you are pregnant and your partner has traveled to an area with Zika, then the CDC recommend you use barrier contraceptive methods or abstain from sex for the rest of your pregnancy, regardless of whether your partner has symptoms or not. In most men, the Zika virus lingers in semen for no longer than three months; however, experts still consider it best to err on the side of caution and delay pregnancy for at least six months if your partner has recently traveled to a Zika-infected area.

Finished: Zika Virus: Important Questions Answered

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