Zika virus is a mosquito-borne illness that is spread by the Aedes species of mosquito, the mosquito also responsible for the transmission of dengue and chikungunya viruses.^1-3

These mosquitos attack and bite their prey during the daytime hours and can survive in both indoor and outdoor environments.¹

The two known species responsible for Zika transmission are the Aedes albopictus, known as the Asian Tiger mosquito, and the Aedes aegypti species.²

While the symptoms of Zika typically pass within the space of a week, there have been recent concerns about the virus are due to a potential link between Zika and birth defects such as microcephaly.

26 January 2016 update: The Centers for Disease Control and Prevention (CDC) has issued travel warnings for people traveling to areas and certain countries where Zika virus transmission is ongoing. These include:

• Central and South America: Bolivia, Brazil, Colombia, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Panama, Paraguay, Suriname, Venezuela
• Caribbean: Barbados, Dominican Republic, Guadeloupe, Haiti, Martinique, Puerto Rico, Saint Martin, US Virgin Islands
• Oceania: Samoa
• Africa: Cape Verde

Where does Zika virus occur?

Zika virus is transmitted by the Aedes species of mosquito. This species is also responsible for the transmission of dengue.

While the majority of Zika virus cases occur in tropical regions such as Brazil, Colombia, Paraguay, Suriname, Venezuela and French Guiana, the possibility exists of mosquito infection in tropical-like climates in some cities, such as Houston and New Orleans in the US.^1,2,4

Areas within the US which are of concern for potential Zika-infected mosquitos are those with wet lowlands, warmer temperatures and higher levels of poverty.²

Other countries with past or recent Zika virus infection include parts of Africa, Asia, the Americas, Oceania and the Pacific Islands.⁴ Infection in the US is currently linked to exposure of travelers who return from other countries.^1,2

Due to the fact that the species of mosquito that transmits Zika virus can be found throughout the world, the Centers for Disease Control and Prevention (CDC) believe it is likely that outbreaks of the disease will spread to new countries.¹

While Zika virus is known to be transmitted via an infected mosquito, there is a theoretical risk of spread via sexual contact (one confirmed case) or through infected blood.¹

Symptoms of Zika virus

Signs and symptoms of Zika virus are vague and can last for up to a week. Diagnosis of the virus is typically confirmed with a blood test.¹

Symptoms of Zika virus include:^1,2

• Fever
• Rash
• Joint pain
• Conjunctivitis (red eyes)
• Muscle pain
• Headache
• Pain behind the eyes
• Vomiting.

According to the Pan American Health Organization (PAHO), only 1 in 4 people infected with Zika virus develop symptoms.⁵ In contrast, the CDC state the figure is 1 in 5.

In the past, there have also been reports of patients developing Guillain-Barré syndrome following a Zika virus infection. Guillain-Barré syndrome is a rare but serious autoimmune disorder that affects the central nervous system.⁶

Infection with the Zika virus is rarely severe enough to warrant hospitalization, and it is rarer still for an individual to die as a result.⁶

Current research on Zika virus

A growing concern that is currently under investigation is a possible link between maternal Zika virus infection and infant microcephaly.^1-5,7 Brazil in particular has seen a surge in infants born with microcephaly since October 2015, at rates that have been reported to be 10 times higher than those in previous years.⁷

Many people are concerned that there may be a link between maternal Zika virus infection and infant microcephaly.

These infants have been tested for Zika virus with mixed results - some positive and some negative for the virus.⁷ Zika virus has been confirmed to be present in two amniotic fluid samples of microcephalic babies.^2,3

To date, there have been no known transmissions of the virus from mother to infant during breastfeeding.¹

Other regions such as French Polynesia have seen an increase in fetal and newborn brain and spine defects over the past year.³ According to PAHO, "the French Polynesia health authorities hypothesize that Zika virus infection may be associated with these abnormalities if mothers are infected with the virus during the first or second trimester of pregnancy."³

What is microcephaly?

Microcephaly is a neurological condition where an infant's head circumference is significantly smaller than the average size for infants of the same age. Microcephaly can lead to developmental delays in movement and speech among other complications.⁸

Complications of microcephaly include:

• Dwarfism or short stature
• Facial distortion
• Mental retardation
• Hyperactivity
• Seizures.

Microcephaly is believed to be caused by both environmental and genetic factors. While there is currently no direct treatment for microcephaly, supportive therapy can assist infant development.

Treatments for Zika virus

The Centers for Disease Control and Prevention (CDC) report that there is no treatment for the virus.

However, the CDC recommend the following measures for people with the virus:

• Rest
• Increasing fluid intake to prevent dehydration
• Pain and fever relief with medications like acetaminophen or paracetamol.

The CDC advise against using aspirin or other non-steroidal anti-inflammatory medications until a diagnosis of dengue fever has been ruled out due to the risk of hemorrhage.¹

Due to the concerns surrounding infant microcephaly, the CDC have advised that pregnant women who are diagnosed with Zika should be considered for the monitoring of fetal growth and anatomy every 3-4 weeks. They also recommend a referral to a health care professional who specializes in pregnancy management and either infectious disease or maternal-fetal medicine.⁶

Preventing Zika virus

Insect repellent can be used to reduce the risk of mosquito bites.

Since there is currently no vaccine to protect against the disease, avoiding mosquito bites is vital to preventing transmission of Zika virus.^1,4

The CDC recommend using insect repellents, wearing long-sleeved garments and long pants, using window and door screens or running an air conditioner, and emptying areas with collected standing water, as this is a common environment in which mosquitos can lay their eggs.¹

In some cases, mosquito bed netting may be recommended.^1,4 It is recommended specifically that pregnant women traveling to countries which pose a risk for contracting Zika virus avoid mosquito bites.^4,7

When choosing an insect repellent, the CDC recommend using products which contain DEET, picaridin, and IR335. Some products that contain oil of lemon eucalyptus and para-methane-diol can also provide long-lasting protection.^1,4

They also recommend applying insect repellant after the application of sunscreen, treating or wearing clothes treated with permethrin and not using insect repellent under clothing. Always check the instructions for the particular brand of repellant or sunscreen for guidance on use.^1,4

If you are infected with the Zika virus, it is important to avoid being bitten by mosquitos during the first week of infection; the virus can be passed by humans to mosquitos via blood, increasing the risk of spread to others.¹

Travel recommendations for areas affected by Zika virus transmission

Due to current reports from Brazil concerning Zika virus, the CDC have issued a level 2 travel alert (practice enhanced precautions) for people traveling to several countries affected by Zika virus transmission. As of 26 January 2016, the alert is in place for the following countries:⁹

• Barbados
• Bolivia
• Brazil
• Cape Verde
• Colombia
• Dominican Republic
• Ecuador
• El Salvador
• French Guiana
• Guadeloupe
• Guatemala
• Guyana
• Haiti
• Honduras
• Martinique
• Mexico
• Panama
• Paraguay
• Puerto Rico
• Saint Martin
• Samoa
• Suriname
• US Virgin Islands
• Venezuela.

In addition, the CDC also advise that pregnant women consider postponing travel to any of the areas mentioned above. Any who decide to travel to these regions should discuss their journey with a health care provider, as well as measures to prevent mosquito bites.

In general, you are advised to speak with your health care provider if you are planning on traveling to a country in which Zika virus is a concern, as well as if you are experiencing symptoms of Zika virus.