Background

Zika virus is a member of the genus flavivirus (closely related to dengue, yellow fever, Japanese encephalitis and  West Nile viruses) whose primary vector is the Aedes aegypti mosquito (1). Originally identified in Uganda in 1947 in monkeys, Zika was found in humans in 1952 (2).

Transmission can occur in multiple ways, the following ways are the most common:

• Bite of an infected mosquito
• Maternal-fetal transmission
• Sex
• Blood transfusion
• Organ transplantation
• Laboratory exposure (3)

Clinical Presentation

Common signs and symptoms of the Zika virus include fever, rash, joint pain, conjunctivitis, myalgias and headache.  Symptom onset is unclear but is most likely to be a few days and can last from days to weeks (1).  80% of patients exposed to the virus are asymptomatic, but those that are affected will mostly have mild symptoms. Severe complications seem to be rare. Microcephaly in infants born to mothers infected with the virus during pregnancy and Guillain-Barre syndrome are the most serious complications (2)

Testing

The CDC recommends testing for pregnant females who have traveled to areas with active Zika transmission with concern for the infection. Sexual transmission is possible and the CDC recommends testing for those that may have been exposed to Zika through sex having symptoms. Testing men is not recommended to determine if Zika will be transmitted sexually (1). The World Health Organization has expanded the patients that should be tested to include: 

• Patients with sexual contact with a confirmed or probable case
• Patients who meet the case definition of a suspected case with neurological disorders
• Pregnant women with a history of travel to areas with ongoing Zika virus transmission and/or sexual contact with a confirmed or probable case
• Pregnant women from areas with ongoing Zika virus transmission whose fetuses are known, or suspected to have, congenital brain abnormalities
• Neonates with microcephaly or neurological abnormalities born in areas with ongoing Zika transmission or born to women with a history of travel to a Zika-affected area during pregnancy
• Infants with mothers diagnosed with Zika virus, especially if breastfeeding
• Stillbirths or spontaneous abortions from women who have lived in or travelled to a Zika-affected area during the pregnancy (2)
• Couples/women planning on pregnancy should use protection or abstain from sexual intercourse for at least 8 weeks. If men are symptomatic they should adopt safe sex practices for at least 6 months2 as the Zika virus can be present in semen for up to 93 days after onset of illness (3)

Testing that is available include nucleic acid testing (NAT) via RT-PCR. Whole blood, serum or urine can be obtained as long this is within 7 days of symptom onset. Serology examining IgM requires whole blood or serum <5 days of symptom onset. The test needs to be repeated 2-3 weeks later for confirmation (2). For patients being tested >7 days after symptom onset, the preferred method is serology (IgM) testing.

Treatment

Symptomatic treatment is the only recommendation at this point:

• Get plenty of rest
• Drink fluids to prevent dehydration
• Take medicine such as acetaminophen to reduce fever and pain
• Do not take aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs)
• If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication (1)

Prevention

No vaccinations have been approved to date but research is continuing. There is currently a phase I clinical trial in process through the NIH to determine if an immune response will occur with this vaccine.4
Prevention of Zika will be extremely important for people concerned about transmission. The CDC has come up with a list of ways to prevent the transmission that are as follows:

• Wear long-sleeved shirts and long pants when in endemic areas
• Stay in places with air conditioning and window and door screens to keep mosquitoes outside
• Take steps to control mosquitoes inside and outside your home
• Treat your clothing and gear with permethrin or buy pre-treated items 
• Use Environmental Protection Agency (EPA)-registered insect repellents. Always follow the product label instructions
• When used as directed, these insect repellents are proven safe and effective even for pregnant and breastfeeding women 
• Do not use insect repellents on babies younger than 2 months old
• Do not use products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old
• Mosquito netting can be used to cover babies younger than 2 months old in carriers, strollers, or cribs to protect them from mosquito bites
• Sleep under a mosquito bed net if air conditioned or screened rooms are not available or if sleeping outdoors
• Prevent sexual transmission of Zika by using condoms or not having sex (1)

References

1. The Center for Disease Control. Zika Virus http://www.cdc.gov/zika. Aug 4 2016.
2. World Health Organization. Zika Virus.  http://www.who.int. June 2 2016.
3. LaBeaud, A. Zika Virus Infection: an Overview. http://www.uptodate.com/contents/zika-virus-infection-an-overview. Aug 4 2016.
4. The National Institute of Health. Zika Virus. https://www.nih.gov/news-events/news-releases/nih-begins-testing-investigational-zika-vaccine-humans. Aug 3 2016.