Unlike malaria-carrying mosquitos, this species is mostly active during the day and so barrier methods, such as mosquito nets, are less effective.
These mosquitos can survive in both indoor and outdoor environments. The two known species responsible for Zika transmission are the Aedes albopictus, known as the Asian tiger mosquito, and the Aedes aegypti, known as the yellow fever mosquito.
The Zika virus was first identified in monkeys, in Uganda in 1947. The first human cases were detected in Uganda and the United Republic of Tanzania in 1952. Since then, there have been further outbreaks in Africa, South East Asia, and the Pacific Islands.
Fast facts on Zika
- Zika virus cases typically occur in tropical climates.
- Infections in the United States are linked with travel to and from tropical regions.
- Symptoms of Zika virus infection can last for up to 1 week.
- At present, there is no treatment for the virus.
- Avoiding mosquito bites is a key aspect of Zika virus prevention.
Symptoms of Zika virus
Signs and symptoms of Zika virus are vague and can last for up to 1 week. Diagnosis of the virus is typically confirmed with a blood test.
Symptoms of Zika virus include:
In the past, there have also been reports of people 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.
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.
The symptoms of Zika typically pass within the space of 1 week. However, there have been recent concerns about the virus due to a link between Zika and birth defects, such as microcephaly. In light of this, on 1 February 2016, the World Health Organization (WHO) declared that the Zika virus outbreak constituted a Public Health Emergency of International Concern.
On 31 March 2017 the Centers for Disease Control and Prevention (CDC) issued travel warnings for people traveling to certain countries and other areas where Zika virus transmission is ongoing. Travelers, particularly those who are pregnant, who are heading to certain regions should be aware of these warnings. Affected regions include:
- Central and South America
- North America
While the majority of Zika virus cases occur in tropical regions, such as Brazil, Colombia, Paraguay, Suriname, Venezuela, and French Guiana, there is the possibility of mosquito infection in tropical-like climates in some cities in the U.S. Transmission by mosquito has been confirmed in both Texas and Florida.
Areas within the U.S. that are of concern for potential Zika-infected mosquitos are those with wet lowlands, warmer temperatures, and higher levels of poverty. Infection in the U.S. is most frequently linked to exposure of travelers who return from other countries, but is thought in a select few cases to be the result of mosquito transmission.
Due to the fact that the species of mosquito that transmits Zika virus can be found throughout the world, the CDC believe it is likely that outbreaks of the disease will spread to new countries. WHO expects the virus to rapidly spread through the whole of the Americas and some virologists and epidemiologists also believe that Asia will be at risk.
Zika virus travel recommendations
Due to current reports from multiple countries concerning Zika virus, the CDC have issued a level 2 travel alert (practice enhanced precautions) for people traveling to a range of countries, including:
- Costa Rica
- Dominican Republic
- El Salvador
- Puerto Rico
The countries affected change regularly so it is important to check the latest travel information from the CDC.
The Aedes mosquito is not typically found at elevations above 6,500 feet (2,000 meters). As a result, the CDC state that travelers who intend to only be at this level of elevation are unlikely to become infected with the virus from a mosquito. People traveling to an area of low elevation before going to an area of high elevation are still at risk of transmission from mosquitos, however.
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 doctor to determine any risks. They should also take measures to prevent mosquito bites.
Treatments for Zika virus
Currently, there is no treatment or vaccination available for Zika. There are, however, several rapid detection tests available for qualified laboratories, distributed by the CDC. The CDC recommends the following measures for people with the virus:
- increasing fluid intake to prevent dehydration
- relieving pain and fever with medications, such as acetaminophen
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 program every 3-4 weeks.
They also recommend a referral to a doctor that specializes in pregnancy management and either infectious disease or maternal-fetal medicine.
Preventing Zika virus
Zika virus is transmitted by the Aedes species of mosquito. This species is also responsible for the transmission of dengue.
Avoiding mosquito bites is vital to preventing transmission of Zika virus.
The CDC recommend:
- using insect repellents
- wearing long-sleeved garments and long pants
- placing mosquito nets over beds (in some cases)
- using window and door screens
- running an air conditioner
It is also recommended that people empty any areas with collected standing water, as this is a common environment in which mosquitos can lay their eggs.
It is recommended specifically that pregnant women traveling to countries that pose a risk for contracting Zika virus avoid mosquito bites.
When choosing an insect repellent, the CDC recommend:
- Using products that contain DEET, picaridin, and IR335.
- Using products that contain oil of lemon eucalyptus and para-methane-diol, which can also provide long-lasting protection.
They also recommend applying insect repellent:
- after the application of sunscreen
- onto clothes - for example, treating or wearing clothes treated with permethrin
- to under clothing
Always check the instructions for the particular brand of repellent or sunscreen for guidance on use.
What to do if you are infected
If you are infected with the Zika virus, it is important to avoid being bitten by mosquitos during the first week of infection. The Zika virus can be passed from humans to mosquitos via blood, increasing the risk of spread to others.
People traveling home from an area affected by Zika should take steps to prevent mosquito bites for 3 weeks. By taking this precaution, people can help prevent the spread of Zika to uninfected mosquitos at home.
As Zika can be transmitted via sexual contact with a partner who has the virus, the CDC recommend the use of condoms, both during and after traveling to regions affected by Zika virus.
Current facts on Zika virus
The link between maternal Zika virus infection and infant microcephaly is now confirmed. Brazil, in particular, has seen a surge in infants born with microcephaly since October 2015. These rates have been reported to be 10 times higher than those in previous years.
To date, there have been no known transmissions of the virus from mother to infant during breast-feeding.
Other regions such as French Polynesia have seen an increase in fetal and newborn brain and spine defects over the past year. According to the Pan American Health Organization (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."
There is also a potential risk that the Zika virus could spread through infected blood. As a result, the U.S. Food and Drug Administration (FDA) have advised people who have traveled to a region with active Zika virus transmission to defer from donating blood.
Sexually transmitted Zika
Dr. Helen Webberley explained to Medical News Today about another way that the virus could potentially be transmitted:
"What is also of great concern is that the virus has been identified in patients who have not visited these areas and, along with the fact that Zika has been also identified in saliva, urine and semen (where it can exist for up to 2 weeks), raises the distinct possibility that Zika can be transmitted by sexual intercourse."
Some countries are now recommending that men should use condoms for up to 28 days after visiting an "at risk" area if their partners are pregnant or likely to become pregnant if they do not develop symptoms, or for 6 months if they do.
The CDC state that men with a pregnant partner who have traveled to an "at risk" area should either:
- Abstain from sexual activity - vaginal, anal, or oral.
- Use condoms - consistently and correctly use condoms for the duration of the pregnancy.