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Mains Articles

Zika Virus

All you need to know about an another infectious disease outbreak.
By IT' Mains Articles Team
April 11, 2016

Contents

  • What is Zika virus disease?
  • How do people become infected?
  • Signs and Symptoms
  • Transmission
  • Treatment
  • Diagnosis
  • Potential complications of Zika virus disease [Guillain-Barré syndrome & Microcephaly]
  • How is Zika related to microcephaly?
  • Recent Study
  • Prevention
  • WHO response
  • El Niño and Zika virus
  • Spread of Zika
  • Any case of Zika in India?
  • India’s preparedness in context of Zika
  • Timeline of Zika

Global health officials are racing to better understand the Zika virus behind a major outbreak that began in Brazil last year and has since spread to many countries in the Americas.

 

All About Zika Virus Disease

What is Zika virus disease?

  • Zika virus disease is caused by a virus transmitted by Aedes mosquitoes.  

How do people become infected?

  • Zika is transmitted to people through the bite of infected female mosquitoes, primarily the Aedes aegypti mosquito, the same type that spreads dengue, chikungunya and yellow fever.

Signs and Symptoms

  • The incubation period (the time from exposure to symptoms) of Zika virus disease is not clear, but is likely to be a few days.
  • People infected with Zika may have a mild fever, skin rash, conjunctivitis, muscle and joint pain and fatigue that can last for two to seven days. But as many as 80 percent of people infected never develop symptoms.
  • The symptoms are similar to those of dengue or chikungunya, which are transmitted by the same type of mosquito.
  • These symptoms are usually mild and last for 2-7 days.

Main culprit: Aedes aegypti, the mosquito responsible for the Zika virus

Aedes mosquitoes

The Pan American Health Organization (PAHO) said Aedes mosquitoes are found in all countries in the Americas except Canada and continental Chile, and the virus will likely reach all countries and territories of the region where Aedes mosquitoes are found

Zika Virus 4.jpg.jpg Zika Virus

Transmission

  • Zika virus is transmitted to people through the bite of an infected mosquito from the Aedesgenus, mainly Aedes aegypti in tropical regions.
  • This is the same mosquito that transmits dengue, chikungunya and yellow fever.
  • However, sexual transmission of Zika virus has been described in 2 cases, and the presence of the Zika virus in semen in 1 additional case. On February 27, France said it had detected its first sexually transmitted case of Zika in a woman whose partner had traveled to Brazil.

Zika Virus 5.jpg

  • A mother already infected with Zika virus near the time of delivery can pass on the virus to her newborn around the time of birth.
  • A pregnant woman can pass Zika virus to her fetus during pregnancy.
  • To date, there are no reports of infants getting Zika virus through breastfeeding. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas where Zika virus is found.
  • Anyone who lives in or travels to an area where Zika virus is found and has not already been infected with Zika virus can get it from mosquito bites. Once a person has been infected, he or she is likely to be protected from future infections.

Treatment

  • Zika virus disease is usually relatively mild and requires no specific treatment. People sick with Zika virus should get plenty of rest, drink enough fluids, and treat pain and fever with common medicines. If symptoms worsen, they should seek medical care and advice. There is currently no vaccine available.
  • Companies and scientists are racing to develop a safe and effective vaccine for Zika, but the World Health Organization (WHO) said it would take at least 18 months to start large-scale clinical trials of potential preventative shots.

Diagnosis  

  • Zika virus diagnosis can only be confirmed by laboratory testing for the presence of Zika virus RNA in the blood or other body fluids, such as urine or saliva.
  • Infection with Zika virus may be suspected based on symptoms and recent history (e.g. residence or travel to an area where Zika virus is known to be present).

Potential complications of Zika virus disease [Guillain-Barré syndrome & Microcephaly]  

  • During large outbreaks in French Polynesia and Brazil in 2013 and 2015 respectively, national health authorities reported potential neurological and auto-immune complications of Zika virus disease.
  • Recently in Brazil, local health authorities have observed an increase in Guillain-Barré syndrome (a rare neurological disorder that can result in paralysis) which coincided with Zika virus infections in the general public, as well as an increase in babies born with microcephaly in northeast Brazil.
  • The PAHO said there is no evidence that Zika can cause death, but some cases have been reported with more serious complications in patients with pre-existing medical conditions.Zika Virus 6.jpg

How is Zika related to microcephaly?

  • According to the World Health Organization, there is a strong scientific consensus that Zika can cause the birth defect microcephaly in babies, a condition defined by unusually small heads that can result in developmental problems. In addition, the agency said it could cause Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis, though conclusive proof may take months or years.

microcephaly-comparison-triple-350px  Main.jpg

  • Brazil said it has confirmed 944 cases of microcephaly, and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,291 suspected cases of microcephaly.
  • Research in Brazil indicates the greatest microcephaly risk is associated with infection during the first trimester of pregnancy.

Recent Study

  • According to a new study conducted in lab-grown human cells, a Zika virus-laden mosquito bite may infect and kill a type of brain cell, vital for the development of the brain.
  • The researchers applied the Zika virus to the lab-grown brain cells and found that the virus infected and spread through a plate of these cells within a span of three days. Also, it killed the cells or disrupted their growth.

Prevention

Mosquitoes and their breeding sites pose a significant risk factor for Zika virus infection. Prevention and control relies on reducing mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people.This can be done by

  • Using insect repellent regularly;
  • Wearing clothes (preferably light-coloured) that cover as much of the body as possible;
  • Using physical barriers such as window screens, closed doors and windows; and
  • If needed, additional personal protection, such as sleeping under mosquito nets during the day.
  • It is extremely important to empty, clean or cover containers regularly that can store water, such as buckets, drums, pots etc.
  • Other mosquito breeding sites should be cleaned or removed including flower pots, used tyres and roof gutters. Communities must support the efforts of the local government to reduce the density of mosquitoes in their locality.
  • The World Health Organization (WHO) said sexual transmission is “relatively common” and has advised pregnant women not to travel to areas with ongoing outbreaks of Zika virus.

Zika Virus 7.jpg

  • The World Health Organization (WHO) said sexual transmission is “relatively common” and has advised pregnant women not to travel to areas with ongoing outbreaks of Zika virus.
  • Repellents should contain DEET (N, N-diethyl-3-methylbenzamide), IR3535 (3-[N-acetyl-N-butyl]-aminopropionic acid ethyl ester) or icaridin (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-methylpropylester). Product label instructions should be strictly followed.
  • Special attention and help should be given to those who may not be able to protect themselves adequately, such as young children, the sick or elderly.
  • During outbreaks, health authorities may advise that spraying of insecticides be carried out. Insecticides recommended by the WHO Pesticide Evaluation Scheme may also be used as larvicides to treat relatively large water containers.
  • Travellers should take the basic precautions described above to protect themselves from mosquito bites.

WHO response

Logo-WHO

WHO is supporting countries to control Zika virus disease through:

  • Define and prioritize research into Zika virus disease by convening experts and partners.
  • Enhance surveillance of Zika virus and potential complications.
  • Strengthen capacity in risk communication to help countries meet their commitments under the International Health Regulations.
  • Provide training on clinical management, diagnosis and vector control including through a number of WHO Collaborating Centres.
  • Strengthen the capacity of laboratories to detect the virus.
  • Support health authorities to implement vector control strategies aimed at reducing Aedes mosquito populations such as providing larvicide to treat still water sites that cannot be treated in other ways, such as cleaning, emptying, and covering them.
  • Prepare recommendations for clinical care and follow-up of people with Zika virus, in collaboration with experts and other health agencies.

El Niño and Zika virus

The Aedes aegypti mosquito breeds in still water. Severe drought, flooding, heavy rains and temperature rises are all known effects of El Niño—which is the result of a warming of the central to eastern tropical Pacific Ocean.

An increase in mosquitoes can be expected due to expanding and favourable breeding sites. Steps can be taken to prevent and reduce the health effects of El Niño.

Spread of Zika  

         0.07406000_1455624901_32-2-20160229 Image Courtesy: DownToEarth
  • Zika virus disease outbreaks were reported for the first time from the Pacific in 2007 and 2013 (Yap and French Polynesia, respectively), and in 2015 from the Americas (Brazil and Colombia) and Africa (Cabo Verde). In addition, more than 13 countries in the Americas have reported sporadic Zika virus infections indicating rapid geographic expansion of Zika virus.
  • Active Zika outbreaks have been reported in at least 41 countries or territories, most of them in the Americas, according to the US Centers for Disease Control and Prevention (CDC).
  • Brazil has been the country most affected.

Any case of Zika in India?

 

Though, no case of Zika has been reported in India so far, the virus has a history in the country. The prevalence studies on the Zika virus had been carried out as early as in 1952-53 by the National Institute of Virology (NIV), Pune and showed presence of antibodies in humans in several parts of central and western India.

zika and india

India’s preparedness in context of Zika  

The declaration of the emergency by WHO has made India take notice of the threat.

  • On February 2, the Union Ministry of Health and Family Welfare issued guidelines on managing the Zika virus and appointed the National Centre for Disease Control in Delhi as the nodal agency for investigating outbreaks in the country. 

National-Centre-for-Disease-control-to-hire-Lab-Attendant.jpg

  • The ministry has also issued travel advisories and suggested that people avoid non-essential travel to affected countries.
  • According to the guidelines, pregnant women or women who are planning pregnancy should defer travelling to the affected areas.
  • It suggests that travellers diagnosed with fever within two weeks of return from an affected country should report to the nearest health facility. 
  • The guidelines also call for pregnant women who have travelled to Zika-affected areas to mention their travel during antenatal visits in order to be assessed and monitored appropriately.
  • For enhancing surveillance, the Integrated Disease Surveillance Programme (IDSP), through its community and hospital-based data gathering mechanism, would keep track of areas where a large number of cases of acute fever are reported.

IDSP

  • IDSP would also advise its state- and district-level units to look for clustering of cases of microcephaly among newborns and reporting of Guillain-Barré Syndrome.
  • The Maternal and Child Health Division (under National Health Mission) would also advise its field units to look for clustering of cases of microcephaly among newborns.

Timeline of Zika

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