Zika Virus - A Rapid Advise
Jagdish Kathwate
(MD Peds), Associate Editor, Pediatric Oncall
First Created: 02/10/2016 

Introduction

The World Health Organization has declared the Zika virus an international public health emergency, prompted by growing concern that it could cause birth defects. As many as four million people could be infected by the end of the year. Officials at the Centers for Disease Control and Prevention have urged pregnant women against travel to about two dozen countries, mostly in the Caribbean and Latin America, where the outbreak is growing.

Countries Affected By Zika Virus

  1. Bolivia
  2. Brazil
  3. Colombia
  4. Commonwealth of Puerto Rico, US territory
  5. Costa Rica
  6. Curacao
  7. Dominican Republic
  8. Ecuador
  9. El Salvador
  10. French Guiana
  11. Guadeloupe
  12. Guatemala
  13. Guyana
  14. Haiti
  15. Honduras
  16. Martinique
  17. Mexico
  18. Nicaragua
  19. Panama
  20. Paraguay
  21. Saint Martin
  22. Suriname
  23. U.S. Virgin Islands
  24. Venezuela
  25. American Samoa (Oceana/Pacific Islands)
  26. Samoa (Oceana/Pacific Islands)
  27. Cape Verde (Africa)

Zika Virus - Pathogenesis

Zika virus is primarily transmitted to humans through bites from Aedes mosquitos, which often live around buildings in urban areas and are usually active during daylight hours (peak biting activity occurs in early mornings and late afternoons).

Some evidence suggests the Zika virus can also be transmitted to humans through blood transfusion, perinatal transmission and sexual transmission. However, these modes are very rare.

The incubation period is typically between 2 and 7 days.

Clinical Features

Zika virus infection is characterized by low-grade fever (less than 38.5°C) frequently accompanied by a maculopapular rash. Other common symptoms include muscle pain, joint pain with possible swelling (notably of the small joints of the hands and feet), headache, pain behind the eyes and conjunctivitis. As symptoms are often mild, the infection may go unrecognized or be misdiagnosed as dengue. A high rate of asymptomatic infection with the Zika virus is expected, similar to other flaviviruses, such as dengue virus and West Nile virus. Most people fully recover without severe complications, and hospitalization rates are low. To date, there have been no reported deaths associated with the Zika virus.

The Brazil Ministry of Health is also investigating the possible association between the Zika virus and a reported increase in the number of babies born with microcephaly. Due to concerns of microcephaly associated with maternal Zika virus infection, fetuses and infants of women infected with Zika virus during pregnancy should be evaluated for possible congenital infection and neurologic abnormalities

Investigations

Several methods can be used for diagnosis, such as viral nucleic acid detection, virus isolation and serological testing. Nucleic acid detection by reverse transcriptase-polymerase chain reaction targeting the non-structural protein 5 genomic region is the primary means of diagnosis, while virus isolation is largely for research purposes. Saliva or urine samples collected during the first 3 to 5 days after symptom onset, or serum collected in the first 1 to 3 days, are suitable for detection of the Zika virus by these methods. Serological tests, including immunofluorescence assays and enzyme-linked immunosorbent assays, may indicate the presence of anti-Zika virus IgM and IgG antibodies. Caution should be taken with serological results as IgM cross-reactivity with other flaviviruses has been reported in both primary infected patients and those with a probable history of prior flavivirus infection.

Treatment

There is no commercial vaccine or specific antiviral drug treatment for the Zika virus infection. Treatment is directed primarily at relieving symptoms using antipyretics and analgesics.

Vaccine to Prevent Zika Virus Infection

No, not yet but recently Bharat Biotech, a vaccines and bio-therapeutic manufacturer claimed to have achieved a breakthrough in developing a vaccine to fight the dreaded mosquito-borne Zika virus.

Prevention and Control

The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for the Zika virus infection. Prevention and control rely on reducing the breeding of mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people.

This can be achieved by reducing the number of natural and artificial water-filled habitats that support mosquito larvae, reducing the adult mosquito populations around at-risk communities, and using barriers such as repellants, insect screens, closed doors and windows, and long clothing. Since the Aedes mosquitoes are day-biting mosquitoes, it is recommended that those who sleep during the daytime, particularly young children, the sick or elderly, should use insecticide-treated mosquito nets to provide protection. Mosquito coils or other insecticide vaporizers may also reduce the likelihood of being bitten.

During outbreaks, space spraying of insecticides may be carried out periodically to kill flying mosquitoes. Suitable insecticides (recommended by the WHO Pesticide Evaluation Scheme) may also be used as larvicides to treat relatively large water containers. Basic precautions for protection from mosquito bites should be taken by people traveling to high-risk areas. These include the use of repellents, wearing light-colored, long-sleeved shirts and pants and ensuring rooms are fitted with screens to prevent mosquitoes from entering.


1. Factsheet about zika virus from WHO available on http://www.wpro.who.int/mediacentre/factsheets/fs_05182015_zika/en

Zika Virus - a Rapid Advise Zika Virus - a Rapid Advise 02/10/2016
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