Zika Virus

Context: In response to reported cases of the Zika virus in parts of Maharashtra, the Union Health Ministry issued a nationwide advisory, emphasizing the importance of continuous vigilance. The advisory urges states to prioritize screening pregnant women for the Zika virus and to closely monitor the fetal development of those who test positive for the infection.

About Zika Virus: 

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  • Zika virus is a mosquito-borne virus first identified in Uganda in 1947 in a Rhesus macaque monkey followed by evidence of infection and disease in humans in other African countries in the 1950s.
  • Since 2007 outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.
  • In outbreaks over the last decade Zika virus was found to be associated with increased incidence of Guillain-Barré syndrome.
    • It is a serious autoimmune disorder that affects the peripheral nervous system.
    • It initially presents weakness, tingling, and numbness in the limbs, which can progress to paralysis lasting 6-12 months or longer.
    • The syndrome affects the nerves responsible for muscle movement, pain, temperature, and touch sensations.
    • While more common in adults and males, it  can occur in individuals of all ages.
  • Outbreaks of Zika virus disease were identified throughout most of the Americas and in other regions with established Aedes Aegypti mosquitoes.
  • Sexual transmission has been confirmed as an alternate route of Zika virus infection.
  • There is no specific treatment available for Zika virus infection or disease.
  • In 2016 WHO declared the Zika virus and microcephaly as Public Health Emergency of International Concern (PHEIC).

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Structure of the Virus: 

  • A team led by Dr. Richard Kuhn and Michael Rossmann examined the structure of a mature Zika virus particle at near-atomic resolution.
  • They used a technique called cryo-electron microscopy.
  • Cryogenic electron microscopy (cryo-EM) is a microscopy technique where samples are cooled to cryogenic temperatures.
  • For biological specimens, this involves preserving the structure by embedding it in vitreous ice.
  • Recent improvements in detector technology and software algorithms have enabled the determination of biomolecular structures at near-atomic resolution.
  • These advancements have made cryo-EM a popular alternative to X-ray crystallography and NMR spectroscopy for determining macromolecular structures without requiring crystallization.
  • In 2017, Jacques Dubochet, Joachim Frank, and Richard Henderson were awarded the Nobel Prize in Chemistry for their work in developing cryo-electron microscopy for high-resolution biomolecular structure determination in solution.
  • The Zika virus, a single-stranded RNA virus from the Flaviviridae family. 
    • Flaviviridae is a family of enveloped positive-strand RNA viruses that primarily infect mammals and birds.
    • These viruses are mainly transmitted through arthropod vectors, particularly ticks and mosquitoes.
  • The virus has two major lineages: Asian and African, which are geographically distinct.
    • The African lineage primarily infects monkeys and apes, with humans as secondary hosts. 
    • The Asian lineage primarily affects humans.
  • The RNA of the Zika virus translates into a single polyprotein:
    • Encoding three structural proteins, which are capsid (C), membrane (M), and envelope (E). The structural proteins form the viral particle
    • Along with seven non-structural proteins. Non-structural proteins assist in genome replication, packaging, and manipulating host processes to benefit the virus.


  • Zika virus infection during pregnancy is a cause of microcephaly and other congenital malformations in the infant, including limb contractures, high muscle tone, eye abnormalities and hearing loss. These clinical features are collectively referred to as congenital Zika syndrome.
    • Microcephaly is a birth defect in which babies are born with a smaller than usual head and underdeveloped brain
  • Congenital malformations occur following both symptomatic and asymptomatic infection. 
  • Zika infection in pregnancy can also cause complications such as fetal loss, stillbirth and preterm birth.  
  • Zika virus infection can also cause Guillain-Barré syndrome, neuropathy and myelitis, particularly in adults and older children.


  • Zika virus is primarily transmitted by infected mosquitoes of the Aedes (Stegomyia) genus, mainly Aedes aegypti, in tropical and subtropical regions. Aedes mosquitoes usually bite during the day.
  • These mosquitoes also transmit dengue, chikungunya and urban yellow fever.
  • Zika virus is also transmitted from mother to fetus during pregnancy, as well as through sexual contact, transfusion of blood and blood products, and possibly through organ transplantation.

Prelims Previous Year Question (2017):

Q. Consider the following statements:

1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue. 2. Sexual transmission of Zika virus disease is possible.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c)

Practice Question for Prelims: 

Q. With reference to Zika Virus, consider the following statements:

1. Cryo-electron microscopy was utilised to reveal the near-atomic structure of the Zika virus.

2. The Zika virus is a double-stranded DNA virus from the Flaviviridae family.

3. The African Lineage of Zika Virus primarily affects humans.

Which of the statements given above is/are correct?

(a) 1 and 2 only

(b) 2 only

(c) 1 only

(d) 1 and 3 only

Answer: (c)

1st statement is correct: A team led by Dr. Richard Kuhn and Michael Rossmann examined the structure of a mature Zika virus particle at near-atomic resolution. They used a technique called cryo-electron microscopy.

2nd statement is not correct: The Zika virus, a single-stranded RNA virus from the Flaviviridae family, has two major lineages: Asian and African, which are geographically distinct.

3rd statement is not correct: The African lineage primarily infects monkeys and apes, with humans as secondary hosts. The Asian lineage primarily affects humans.

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