zika%20virus%20infection
ZIKA VIRUS INFECTION

Zika virus is an icosahedral, enveloped, single-stranded RNA virus that come from the Flaviviridae family & genus Flavivirus.

It is transmitted in humans through a bite of Aedes aegypti & Aedes albopictus mosquito.

In February 2016, the Zika virus infection was declared by the World Health Organization (WHO) as an international health emergency.

Pregnant women infected by Zika virus may pass their infection to the developing fetus & may cause birth defects such as microcephaly, ventriculomegaly, intracranial calcifications, extra-axial fluid, polymicrogyria, decreased brain parenchymal volume, hypoplasia of the cerebellum, brainstem or dermis, delayed myelination, thinning or hypoplasia of the corpus callosum & cortical atrophy & malformation.

 

 

Introduction

  • Zika virus infection is an arboviral and a notifiable disease
  • All healthcare professionals are encouraged to report suspected cases to the state and local health departments to facilitate the diagnosis and mitigate the risk of transmission

Etiology

  • Zika virus is an icosahedral, enveloped, single-stranded RNA virus that come from the Flaviviridae family and genus Flavivirus
    • Its lipid envelope is covered with dense projections consisting of membrane and glycoproteins

Pathophysiology

Mode of Transmission

  • It can primarily be transmitted in humans through a bite of Aedes aegypti and Aedes albopictus mosquito
    •  Other Aedes species that can transmit infection are Aedes africanusAedes luteocephalusAedes vittatusAedes furciferAedes hensilli and Aedes apicoargenteus
      • These mosquito vectors breed in domestic water-holding containers
      • They are aggressive daytime biters
      • Peak biting hours: Early in the morning and late afternoon/evening
      • Feed both indoors and outdoors especially near dwellings
      • Main reservoirs of the virus: Nonhuman and human primates
      • During outbreaks, anthroponotic transmission (human-to-vector-to-human) may occur
  • Other possible modes of transmission:
    • Perinatal
    • Sexual (anal, vaginal and oral)
      • May be transmitted from male-to-male, male-to-female- and female-to-male sex partners
      • At present, female-to-female transmission has not been documented
      • Women infected with Zika may pass the virus through vaginal fluid and menstrual blood
    • Blood transfusion
    • Organ transplantation
    • Laboratory exposure

Epidemiology

  • First identified in Zika forest of Entebbe in Uganda in 1947 in Rhesus monkey and isolated in humans in 1952 in Uganda and Tanzania
  • It was in 2007 that the first outbreak happened in the Yap Islands of Micronesia that affected >70% of the population aged 3 years old and above
  • In 2013 to 2014, the second outbreak occurred in French Polynesia which affected ⅔ of the population
    • 3% of the donated blood samples tested were positive for Zika virus
  • Countries and territories that are known to have local mosquito-borne transmission of Zika virus are: East Timor, Ecuador, El Salvador, Fiji, French Guiana, Grenada, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Indonesia, Jamaica, Kosrae (Federated States of Micronesia), Laos, Malaysia, Maldives, Marshall Islands, Martinique, Mexico, Myanmar, New Caledonia, Nicaragua, Palau, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Saba, Samoa, Saint Barthélemy, Saint Kitts and Nevis, Saint Lucia, Saint Martin, Saint Vincent and Grenadines, Singapore, Saint Eustatius, Saint Maarten, Suriname, Thailand, Tonga, Trinidad and Tobago, Turks and Caicos, United States, Venezuela, Vietnam, Anguilla, Antigua and Barbuda, Argentina, Aruba, Bahamas, Barbados, Belize, Bolivia, Bonaire, Brazil, British Virgin Islands, Brunei, Cambodia, Cape Verde, Cayman Islands, Colombia, Costa Rica, Cuba, Curaçao and Dominica and Dominican Republic
  • It was in early 2015 that Zika virus was first identified in Brazil
    • This was also when the Zika virus has rapidly spread throughout the Americas
  • In mid to late 2015, cases of microcephaly Guillain-Barré syndrome were increased and reported in northern Brazil
  • In May 2015, the first local transmission of Zika virus in the Western Hemisphere was reported by World Health Organization (WHO)
  • In February 2016, the Zika virus infection was declared by the World Health Organization (WHO) as an international health emergency
  • On September 7, 2016, the first Zika infection in pregnancy was reported in Malaysia

Signs and Symptoms

  • Zika virus infection is mild and self-limiting
  • Incubation period is 3-12 days
  • May present with:
    • Conjunctivitis
    • Acute onset of mild or low-grade fever
    • Arthralgia (eg particularly on the small joints of the hands and feet)
    • Headache
    • Retro-orbital pain
    • Skin rash (eg maculopapular rashes that are fine and diffusely distributed on the face, trunk, extremities, palms and soles)
  • Symptoms may appear on the 1st week of illness, last for up to 2-7 days and occur for 2 weeks
  • May overlap with other arboviral infections but the presence of maculopapular and immune-mediated rash predominates

Risk Factors

  • Zika virus transmission and infection are increased in patients with Guillain-Barré syndrome (GBS)
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