Understanding Zika Virus

Zika virus is one of the hottest topics in the news today. While we are learning much about this virus, there is still a lot that is unclear. The current hype is due to the potential link between Zika virus infection during pregnancy and birth defects. There is also a potential link between Zika and Guillain-Barré Syndrome, a neurological condition that can attack anyone, not just pregnant women.

What is Zika?

Zika is a virus that is classified as an arbovirus. People who become infected by the virus contract Zika virus disease. Zika virus is related to the viruses that cause dengue, yellow fever, and West Nile. Zika virus is primarily transmitted by the Aedes aegypti mosquito, with the potential of transmission from the Aedes albopictus mosquito as well. While the virus was first discovered in 1947, little was known about it because human infection was rare. The first large outbreak occurred in 2007 in Micronesia, followed by an outbreak in French Polynesia in 2013. The first documentation in the Americas was on Easter Island in 2014, followed by the first cases in Brazil in 2015.

To date, there have been no cases in the US except for Americans who have travelled to endemic regions and returned with the infection. Puerto Rico, a US territory, has documented cases acquired on the island.

The Center for Disease Control and Infection (CDC) publishes a map where Zika virus infections occur. This is available at: http://www.cdc.gov/zika/geo/index.html

How do you get Zika? Is it contagious?

The primary source of Zika virus is mosquitoes in endemic areas, as mentioned above. The virus has been shown to survive in sperm, and there have been a few cases of females contracting the infection from their male partners. Zika virus has also been detected in the blood of blood donors who did not have symptoms, suggesting that infected blood may also transmit the virus, although there are no known cases of this. There is currently no evidence that infection can spread through saliva, urine or through the air.

How do I know if I have been infected? How is it treated?

Diagnosis is tricky, as currently there is no commercially available test, and the tests the CDC use are not 100% accurate. Also, as many as 80% of people who contract the virus may have no symptoms. For those who do develop symptoms, they are usually mild and resemble the flu. On average, symptoms develop between 3 and 12 days after a mosquito bite and include:

  • Fever
  • Conjunctivitis (red eyes)
  • Arthralgia/Myalgia (joint and muscle aches and pains)
  • Widespread rash, which may be itchy
  • Headache
  • Upset stomach, including diarrhea or constipation

The most common symptoms are the first 3, and they typically last 2 to 7 days. Serious medical conditions, including death, are extremely rare.

There is no treatment for Zika virus other than making symptoms more manageable. This would include drinking plenty of fluids to avoid dehydration and taking Acetaminophen or similar medications to treat fever and body aches.

So why all the fuss about Zika?

While the symptoms of infection are mild or non-existent, there is some evidence that Zika infection during pregnancy can cause a birth defect called microcephaly. In this condition, the fetal brain does not develop properly which results in a smaller than normal head size. Children with microcephaly often have intellectual disabilities. Severe cases can result in seizures or death. There is also evidence that Zika infection can cause a neurological condition called Guillain-Barré syndrome, which if left untreated can also result in death.

These problems were first noted in Brazil, where there was an increase in the number of reported cases of microcephaly around the same time as the Zika outbreak. It is unclear if this represents a true increase in cases, or if the incidence has gone up because more cases are being reported. Experts who looked back to the infection outbreak in French Polynesia have also noted an increase in cases of microcephaly during that outbreak.

While statistics seem to support a correlation between Zika infection and microcephaly, currently we do not have an explanation as to how the virus could cause this condition. It is also important to note that Colombia, which has reported over 5,000 cases of Zika infection in pregnant women since October 2015, has yet to report a single case of microcephaly.

Is there a way to prevent Zika virus?

There is currently no vaccination against Zika virus. Many countries are looking at mass prevention by spraying insecticides or using other methods to control the mosquito population. The CDC recommends US residents strongly consider avoiding travel to areas of known Zika infection, especially if pregnant or if trying to become pregnant.

If travelling to an area of known Zika transmission, avoidance of mosquitoes is particularly important. Remember that the mosquito that transmits Zika also transmits Dengue and Chikungunya, which are also serious diseases. To best avoid mosquito bites:

  • Avoid going outdoors, particularly at dusk and dawn when mosquitoes are most prevalent
  • Remain indoors in areas with air conditioning or that use screens on doors and windows
  • Wear light-colored pants and shirts with long-sleeves
  • Avoid areas of stagnant water, where mosquitoes are present in greater number
  • Use mosquito nets if sleeping/camping outdoors. If travelling with children, these nets can be draped over strollers to protect them
  • Use insect repellent. Any EPA-approved repellant is safe to use in pregnancy and for children if the directions are followed appropriately. This includes repellents with DEET or permethrin. It is best to use these repellents on clothing instead of directly on skin. Permethrin-treated clothing is particularly effective, even after multiple washes.
  • When using sunscreen, apply the sunscreen first and then apply insect repellant
  • Because of the possibility of sexual transmission, pregnant women should abstain from sex or have sex with appropriate condom use through the remainder of the pregnancy
  • If you are bitten by a mosquito in an endemic area, you should see your doctor

 

References

American Academy of Family Physician. Zika Virus Outbreak (2016) http://www.aafp.org/patient-care/public-health/zika-virus.html. Accessed May 2016

Basarab M, Bowman C, Aarons, E, et al. Zika Virus. BMJ (2016);352:i1049 doi:10.1136/bmj.i1049

Center for Disease Control and Prevention. Zika Virus. http://www.cdc.gov/zika/index.html. Accessed May 2016

Chang C, et al., The Zika outbreak of the 21st century, Journal of Autoimmunity (2016), http://dx.doi.org/10.1016/j.jaut.2016.02.006

Mlakar J, Korva, M, Tul N, et al. Zika Virus Associated with Microcephaly. New England Journal of Medicine (2016). 374:951-958 doi:10.1056/NEJMoa1600651

 

March 2016. This post was authored by Adrian Zamora, University of Illinois at Chicago medical student and Susan Buchanan, MD, MPH, Director of the Great Lakes Center for Children’s Environmental Health – Region 5 Pediatric Environmental Health Specialty Unit (PEHSU).

 

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