Zika virus infection


A member of the Flaviviridae virus family and the Flavivirus genus; includes dengue, west Nile, yellow fever, and Japanese encephalitis viruses.

It is transmitted by aedes mosquitoes.

Sexual transmission is possible but is much less common than mosquito transmitted infections.

A category of RNA genome virus that has an envelope.

It initially causes a mild illness known as Zika fever.

Been known to occur within a narrow equatorial belt from Africa to Asia.

In Central America, the Caribbean, and South America, the Zika outbreak has reached pandemic levels.

Symptomatically the illness is nearly always mild, self-limiting with fever, rash, joint pain and conjunctivitis.

It is a self-limiting dengue like illness, with symptoms including fever, rash, headache, and arthralgia.

The infection can be transmitted across the placenta to the developing fetus with potential teratogenic effects, including CNS anomalies.

Most fetuses with prenatal Zika virus exposure present without detectable clinical anomalies, while some congenital infected offspring can have mild, moderate, or severe adverse outcomes collectively referred to as the congenital Zika syndrome.

The Zika syndrome encompasses a wide spectrum of abnormalities-cortical atrophy with microcephaly, functional impairments such as  dysphagia, and sequelae as epilepsy.

Congenital infection associated with a high incidence of bilateral macular and optic nerve problems.

The Zika virus is related to dengue, yellow fever, Japanese encephalitis, and West Nile viruses.

The illness is similar to a mild form of dengue fever.

Most cases are asymptomatic.

Incubation period 3 days to 2weeks.

Treated by rest.

Cannot yet be prevented by drugs or vaccines.

Link between Zika fever and microcephaly in newborn babies of infected mothers.

There is a higher risk of death among children with congenital Zika syndrome than among those without the syndrome, and the risk persists throughout the first three years of life.

Linked with neurologic conditions in infected adults, including cases of the Guillain–Barré syndrome.

In January 2016, the U.S. Centers for Disease Control and Prevention (CDC) issued travel guidance with the use of enhanced precautions, and guidelines for pregnant women including considering postponing travel.

Other governments or health agencies advise women to postpone getting pregnant until more is known about the risks.

Enveloped and icosahedral with a nonsegmented, single-stranded, positive-sense RNA genome.

It is thought that viral replication occurs in the local dendritic cells after the inoculation from mosquito with subsequent spread to lymph nodes in the bloodstream.

Viremia seen 3-4 days of symptom onset.

Viruses detectable in blood is early as the day of illness onset and as late as 11 days after onset.

Virus has been detected in urine, sperm, and saliva of infected individuals.

Hypothesized to start with an infection of dendritic cells near the site of inoculation, followed by a spread to lymph nodes and the bloodstream.

Flaviviruses generally replicate in the cytoplasm.

Zika virus antigens have been found in infected cell nuclei.

There are two lineages of Zika virus, the African lineage and the Asian lineage.

Aedes aegypti is a mosquito vector of Zika virus.

Female Aedes aegypti mosquitos are the most likely to transmit the virus.

A. aegypti is the major objective for horizontal transmission of Zika virus to humans.

Aedes albopictus mosquito are also capable of transmitting virus.

Both species are present in the US.

An infected mosquito can bite and infect 5 or more people in a day.

A albopictus has a much wider range in the US, and has an aggressive daytime activite and thrives in densely populated urban environments.

Zika virus is transmitted by mosquitoes and has been isolated from a number of species in the genus Aedes, such as A. aegypti, and arboreal mosquitoes such as A. africanus, A. apicoargenteus, A. furcifer, A. hensilli, A. luteocephalus, and A. vitattus.

Zika virus can be treated transmitted to humans by non-vectorborne mechanisms such as blood transfusion, sexual contact and as a consequence of maternal fetal transmission.

It is estimated that 1% of Zika virus infections are acquired via sexual transmission.

Incubation period in mosquitoes is about 10 days.

Zika virus can migrate through sexual contact and it can also cross the placenta, affecting an unborn fetus.

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.

The virus has been isolated from sperm, and is associated with transfusions, is detectable in breast milk.

Hosts of the virus are primarily monkeys and humans.

A. aegypti, is expanding due to global trade and travel, and is now the most extensive ever recorded.

The virus is able to pass the placenta.

Common symptoms of infection include.: mild headaches, itchy maculopapular rash, fever, malaise, non purulent conjunctivitis, and joint pains.

It’s features are not clearly distinguishable from mild cases of other arboviral diseases, although rash is more common.

Arthralgias involve small joints of hands and feet.

Myalgias and headache including retro over the pain may be a presentation.

Is relatively mild disease of limited scope, with only one in five persons developing symptoms, with no fatalities.

80% of individuals infected with Zika virus have no symptoms.

Unlike yellow fever and dengue viral infections, death, and hemorrhage , or severe illness requiring hospitalization are rare.

Treatment is symptomatic as no vaccine or preventative drug is available.

Symptoms can be treated with acetaminophen, while aspirin and other nonsteroidal anti-inflammatory drugs should be used only when dengue has been ruled out to reduce the risk of bleeding.

Guillain–Barré syndrome and other neurologic conditione may be complications.

Possible association of Zika virus with congenital microcephaly.

Newborn babies of mothers who had a Zika virus infection during the first trimester of pregnancy are at an increased risk of microcephaly.

Brazilian health authorities reported more than 3,500 microcephaly cases between October 2015 and January 2016.

In the worst affected region of Brazil approximately 1 percent of newborns are suspected of microcephaly.

Associated with serious neurological disease particularly Guillain-Barre syndrome.

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