Zika virus

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Baltimore Classification and Taxonomy

Group IV: (+) sense single-stranded RNA virus

| Order = Unassigned | Family = Flaviviridae | Genus = Flavivirus | species = Zika virus
{|NCBI: Taxonomy Genome: Genome|}

Description and Significance


Zika virus (ZIKV) is a flavivirus that is closely related to dengue, yellow fever, West Nile, and Japanese encephalitis viruses. (ref)

Genome Structure

The Zika virus is a positive sense single-stranded RNA molecule that is 10794 kb long with two non-coding flanking regions. It encodes for a polyprotein that is cleaved to form segments for capsid protein (C), precursor membrane protein (prM), envelope protein (E), and seven other proteins that are not structural (NS). (REF)

Virion Structure of a Zika virus


Reproductive Cycle of a Zika virus in a Host Cell


Viral Ecology


Viral Pathology

Transmission

Mosquito-borne

Human to Human

After returning from a research mission to Senegal, Dr. Brian Foy of the University of Colorado appeared to have passed ZIKV to his wife after sexual intercourse in 2008. Both Dr. Foy and his Ph.D. student Kevin Kobylinski were bitten by numerous mosquitoes while abroad and became ill about 5 days after returning to the U.S. Both showed signs of Zika fever and Dr. Foy's wife saw what she believed to be blood in his semen. Approximately 10 days later, Foy's wife showed signs of Zika fever while their four children remained healthy. At first it was believed that Foy had contracted dengue fever, but after Kobylinski had an encounter with medical entomologist Andrew Haddow who had experience with ZIKV, tests were run that confirmed all three patients possessed antibody for ZIKV. Circumstantial evidence suggests that sexual contact was the mode of transmission due to the high unlikeliness that Foy's wife was bitten by the tropical Aedes mosquito in Colorado. Additionally, the virus requires a 2-week life cycle in mosquito hosts before infecting humans and Foy's wife showed symptoms merely 10 days upon his return. [1]

Zika Fever

Zika fever is the disease associated with ZIKV infection.

Symptoms

The first well-documented case of Zika fever in 1964 describes symptoms as beginning with a headache and then continuing to include a maculopapular rash covering a significant portion of the body the following day. In addition, a fever was present as well as back pain and a general feeling of malaise. [2]

In 1973, a patient with Zika fever presented with fever, joint pain, and headache but the rash was absent. [2]

Another outbreak in Indonesia resulted in all 7 victims showing fever, but varying additional symptoms ranging from abdominal pain and dizziness to diarrhea and anorexia but no signs of rash. [2]

The outbreak on Yap Island showed the maculopapular rash, joint pain, and conjunctivitis. [2]

Diagnosis

Diagnosis for ZIKV infection include PCR tests to detect viral DNA as well as additional tests to detect ZIKV antibody (IgM) in serum. IgM for ZIKV is typically detectable around 3-5 days after infection, but cross-reactivity with closely related dengue, yellow fever, Japanese encephalitis, and West Nile viruses are possible. These cross-reactive results were more common in patients that denoted signs of previous flavivirus infection than patients with primary ZIKV infection. PCR tests should be conducted within 10 days of onset of illness. For best diagnosis practices, serum samples should be analyzed as early as possible with a second test 2 to 3 weeks after that. [2]

Treatment and Prevention

Given that ZIKV is transmitted by mosquitoes, it is advocated by the CDC to use of insect repellent and intervention in reducing the number of mosquito vectors. [2] Additionally, due to recent studies that show the possibility of sexual transmission, safe sex practices are also encouraged.

References

1 Enserink, M. (2011) Sex After A Field Trip Yields Scientific First. Science Magazine

2 Hayes, E. (2009) Zika Virus Outside Africa. CDC Emerging Infectious Diseases