Zika Fever

Zika fever disease is caused by a virus transmitted primarily by Aedes mosquitoes.

• People with Zika virus disease can have symptoms including mild fever, skin rash, conjunctivitis, muscle and joint pain, malaise or headache. These symptoms normally last for 2-7 days.


• There is scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barré syndrome.

Introduction

• Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 in monkeys through a network that monitored yellow fever.


• It was later identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific.


• From the 1960s to 1980s, human infections were found across Africa and Asia, typically accompanied by mild illness.


• The first large outbreak of disease caused by Zika infection was reported from the Island of Yap (Federated States of Micronesia) in 2007.


• In July 2015 Brazil reported an association between Zika virus infection and Guillain-Barré syndrome.


• In October 2015 Brazil reported an association between Zika virus infection and microcephaly.

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. The symptoms are similar to other arbovirus infections such as dengue, and include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache. These symptoms are usually mild and last for 2-7 days.

Complications of Zika virus disease

WHO has concluded that Zika virus infection during pregnancy is a cause of congenital brain abnormalities, including microcephaly; and that Zika virus is a trigger of Guillain-Barré syndrome. Intense efforts are continuing to investigate the link between Zika virus and a range of neurological disorders, within a rigorous research framework.

Transmission

Zika virus is primarily transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions. Aedes mosquitoes usually bite during the day, peaking during early morning and late afternoon/evening. This is the same mosquito that transmits dengue, chikungunya and yellow fever. Sexual transmission of Zika virus is also possible. Other modes of transmission such as blood transfusion are being investigated.

Diagnosis

Infection with Zika virus may be suspected based on symptoms and recent history of travel (e.g. residence in or travel to an area with active Zika virus transmission). A diagnosis of Zika virus infection can only be confirmed through laboratory tests on blood or other body fluids, such as urine, saliva or semen.

Treatment

Zika virus disease is usually 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.

Prevention

Mosquito bites

• Protection against mosquito bites is a key measure to prevent Zika virus infection. This can be done by wearing clothes (preferably light-coloured) that cover as much of the body as possible; using physical barriers such as window screens or closing doors and windows; sleeping under mosquito nets; and using insect repellent containing DEET, IR3535 or icaridin according to the product label instructions. 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. Travellers and those living in affected areas should take the basic precautions described above to protect themselves from mosquito bites.


• It is important to cover, empty or clean potential mosquito breeding sites in and around houses such as buckets, drums, pots, gutters, and used tyres. Communities should support local government efforts to reduce mosquitoes in their locality. Health authorities may also advise that spraying of insecticides be carried out.

Sexual transmission

• Zika virus can be transmitted through sexual intercourse. This is of concern due to an association between Zika virus infection and adverse pregnancy and fetal outcomes.


• For regions with active transmission of Zika virus, all people with Zika virus infection and their sexual partners (particularly pregnant women) should receive information about the risks of sexual transmission of Zika virus. WHO recommends that sexually active men and women be correctly counselled and offered a full range of contraceptive methods to be able to make an informed choice about whether and when to become pregnant in order to prevent possible adverse pregnancy and fetal outcomes. Women who have had unprotected sex and do not wish to become pregnant due to concerns about Zika virus infection should have ready access to emergency contraceptive services and counselling. Pregnant women should practice safer sex (including correct and consistent use of condoms) or abstain from sexual activity for at least the whole duration of the pregnancy.


• For regions with no active transmission of Zika virus, WHO recommends practising safer sex or abstinence for a period of six months for men and women who are returning from areas of active transmission to prevent Zika virus infection through sexual intercourse. Sexual partners of pregnant women, living in or returning from areas where local transmission of Zika virus occurs should practice safer sex or abstain from sexual activity throughout the pregnancy.

What is microcephaly?

Microcephaly is a condition where a baby’s head is smaller than those of other babies of the same age and sex. Microcephaly happens when there is either a problem in utero, causing the baby’s brain to stop growing properly, or after birth when the head stops growing properly. Children born with microcephaly often have developmental challenges as they grow older. In some cases, children with microcephaly develop entirely normally. Microcephaly can be caused by a variety of environmental and genetic factors such as Down syndrome; exposure to drugs, alcohol or other toxins in the womb; and rubella infection during pregnancy.

What is congenital Zika virus syndrome?

• In addition to congenital microcephaly, a range of manifestations has been reported among babies up to 4 weeks old where there has been exposure to Zika virus in utero. These include malformations of the head, involuntary movement, seizures, irritability, brainstem dysfunction such as swallowing problems, limb contractures, hearing and sight abnormalities and brain anomalies. Other outcomes associated with Zika virus infection in utero may involve miscarriages and stillbirths. Together, the spectrum of congenital abnormalities associated with Zika virus exposure of fetuses during pregnancy are known as “congenital Zika virus syndrome.”


• Not all children with congenital Zika virus syndrome present with microcephaly. On the other hand, failure to observe signs of congenital Zika virus syndrome, particularly when assessed in utero, does not necessarily mean that the fetus or newborn does not have abnormalities. For example, hearing abnormalities may not be assessed in utero but only after birth. Some signs such as seizures may develop only after birth.

What is Guillain-Barré syndrome?

Guillain-Barré syndrome is a rare condition in which a person’s immune system attacks his or her nerves. People of all ages can be affected, but it is more common in adult men. Most people recover fully from even the most severe cases of Guillain-Barré syndrome. In 20%-30% of people with the condition, the chest muscles are affected, making it hard to breathe. Severe cases of Guillain-Barré syndrome are rare, but can result in near-total paralysis and/or death.

What is the relationship between Zika and microcephaly and Guillain-Barré syndrome?

Based on a newly published systematic review of current research, WHO has reaffirmed its position that Zika virus infection during pregnancy is a cause of congenital brain abnormalities, including microcephaly, and refined its position on the relationship between Zika virus infection and Guillain-Barré syndrome, stating that Zika virus infection is a trigger of Guillain-Barré syndrome.

What events led WHO to investigate a causal link between Zika virus and complications including microcephaly and Guillian-Barré syndrome?

• A Zika outbreak in Brazil, identified in early 2015, was followed by an unusual increase in microcephaly among newborns, as well as an increased number of cases of Guillain-Barré syndrome. Zika virus outbreaks rapidly affected other countries and territories in the Americas. The scientific community responded with urgency to the rapidly evolving situation and began building a knowledge base about the virus and its implications extremely quickly.


• In 2013-2014, Zika virus had caused an outbreak in French Polynesia with some 28 000 people infected with Zika, including cases of Guillain-Barré syndrome. The outbreaks in the Americas led to a reinvestigation of the 2013-14 outbreak in French Polynesia. Looking back, this outbreak appears to have been linked also to microcephaly.

Are there other explanations for microcephaly and Guillain-Barré syndrome?

• Guillain-Barré syndrome and microcephaly are conditions with a number of underlying causes, triggers and neurological effects.


• Microcephaly can result, among others, from infections during pregnancy, exposure to toxic chemicals and genetic abnormalities.


• Guillain-Barré syndrome is often preceded by an infection. This could be a bacterial or viral infection. The syndrome may also be triggered by vaccine administration or surgery.


• Scientists do not exclude the possibility that other factors may combine with Zika virus infection to cause neurological disorders. A better understanding of Zika virus infection and its complications is one of the remaining research priorities.

Updates on Zika Virus/Fever.

Scientists have found that Zika virus can kill deadly brain cancer cells that are resistant to standard treatments.

• The researchers found that the lethal power of the virus in infecting and killing cells could be directed at malignant cells in the brain.


• It may pave way for an effective treatment for glioblastoma, a deadly form of brain cancer.


• The virus specifically targets and kills neuroprogenitor cells which are rare in the adult brain. Thus it may be safer for use in adults.

Low-cost test to pinpoint Zika virus.

• This test can also detect dengue in blood


• A new test that resembles a pregnancy indicator strip can help detect Zika and dengue viruses in blood, according to a study which used serum samples from several countries including India.


• Researchers checked the accuracy of the test by testing blood serum samples taken from people in Brazil, Colombia, Guatemala, India, Mexico and Panama.


• The paper-strip test contains antibodies that react to the presence of Zika or dengue virus, and gold nanoparticles that respond to the antibody reaction.


• In the light of the problems with the Zika virus causing microcephaly and other defects in babies born to infected mothers, it is important that a pregnant woman know if her fever is caused by Zika virus or dengue virus.


• A medical professional dips the strip, which costs $5 (₹320) per piece, into a tube of either blood serum or whole blood.


• If it is a positive test, then we see a dot or a line on the test that results from the gold nanoparticles that signal the antibodies recognising the viral protein.