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Zika Virus Infection

Zika Virus Infection

Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology belongs to the genus Flavivirus Flavivirus A genus of flaviviridae containing several subgroups and many species. Most are arboviruses transmitted by mosquitoes or ticks. The type species is yellow fever virus. Tick-borne Encephalitis Virus and is primarily transmitted by Aedes aegypti mosquitoes, but can also be transmitted sexually and transplacentally. Although most infected patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship are asymptomatic, some may present with low-grade fever Low-Grade Fever Erythema Infectiosum, pruritic rash Rash Rocky Mountain Spotted Fever, and conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis. Congenital Congenital Chorioretinitis Zika syndrome is the most severe complication of a Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infection, where transplacental fetal infection manifests with ocular defects, microcephaly Microcephaly A congenital abnormality in which the cerebrum is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (desk reference for neuroscience, 2nd ed. ). Fetal Alcohol Spectrum Disorder, spasticity Spasticity Spinal Disk Herniation, and seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures. The diagnosis is made either by RT-PCR RT-PCR A variation of the pcr technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard pcr protocols. Polymerase Chain Reaction (PCR) or serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus. Since there is no definitive management for a Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infection, the treatment is mostly supportive. Prevention includes controlling the mosquito population, using insect repellants, and wearing protective clothing.

Last updated: 31 Mar, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Classification

Rna viruses flowchart classification

RNA virus identification:
Viruses can be classified in many ways. Most viruses, however, will have a genome formed by either DNA or RNA. RNA genome viruses can be further characterized by either a single- or double-stranded RNA. “Enveloped” viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology are covered by a thin coat of cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane (usually taken from the host cell). If the coat is absent, the viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology are called “naked” viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology. Viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology with single-stranded genomes are “positive-sense” viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology if the genome Genome The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics is directly used as messenger RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure ( mRNA mRNA RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3′ end, referred to as the poly(a) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. RNA Types and Structure), which is translated into proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis. “Negative-sense,” single-stranded viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology use RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure-dependent RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure polymerase, a viral enzyme, to transcribe their genome Genome The complete genetic complement contained in the DNA of a set of chromosomes in a human. The length of the human genome is about 3 billion base pairs. Basic Terms of Genetics into messenger RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure.

Image by Lecturio. License: CC BY-NC-SA 4.0

General Characteristics and Epidemiology

General characteristics

  • Genus: Flavivirus Flavivirus A genus of flaviviridae containing several subgroups and many species. Most are arboviruses transmitted by mosquitoes or ticks. The type species is yellow fever virus. Tick-borne Encephalitis Virus
  • Also classified as an arbovirus because it is transmitted by an arthropod
  • Structure:
    • Positive sense
    • Linear ssRNA
    • Enveloped 
    • Icosahedral capsid Capsid The outer protein protective shell of a virus, which protects the viral nucleic acid. Capsids are composed of repeating units (capsomers or capsomeres) of capsid proteins which when assembled together form either an icosahedral or helical shape. Virology
Transmission electron microscopic image of zika virus

Transmission electron microscopic image of Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology:
A member of the family Flaviviridae Flaviviridae A family of RNA viruses, many of which cause disease in humans and domestic animals. There are three genera flavivirus; pestivirus; and hepacivirus, as well as several unassigned species. Hepatitis C Virus, grown in LLC-MK2 culture cells. Virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology particles are 40 nm in diameter, and have an outer envelope Envelope Bilayer lipid membrane acquired by viral particles during viral morphogenesis. Although the lipids of the viral envelope are host derived, various virus-encoded integral membrane proteins, i.e. Viral envelope proteins are incorporated there. Virology and inner dense core. Also note the smooth membrane vesicles Vesicles Female Genitourinary Examination, which are recognized as the replication complex for this virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology family.

Image: “22059” by CDC. License: Public Domain

Epidemiology

  • 1st identified in Uganda in 1947
  • Now widely distributed in the tropical and subtropical zones of: 
  • Local outbreaks Outbreaks Sudden increase in the incidence of a disease. The concept includes epidemics and pandemics. Influenza Viruses/Influenza have recently been reported in the United States.
World map of zika virus risk (2016)

World map showing the distribution of Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology (2016)

Image: “CDC map of Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology distribution as of 15 January 2016” by CDC. License: Public Domain

Related videos

1:06
Flaviviruses

Pathogenesis

Reservoirs

  • Humans
  • Nonhuman primates

Transmission

  • Most commonly transmitted by Aedes aegypti mosquitoes
  • Transplacental transmission can occur if pregnant women are infected.
  • Sexual transmission possible
Aedes aegypti bloodfeeding

Aedes aegypti feeding on human skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions

Image: “Aedes aegypti bloodfeeding CDC Gathany” by James Gathany. License: Public Domain

Host risk factors

  • Recent travel to endemic areas (tropical and subtropical areas)
  • Sexual intercourse with a currently infected or recently infected individual

Pathophysiology

  • The A. aegypti mosquito serves as a vector:
    • Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology replicates within the midgut Midgut Development of the Abdominal Organs of a mosquito.
    • After replication, the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology lives in the salivary glands Salivary glands The salivary glands are exocrine glands positioned in and around the oral cavity. These glands are responsible for secreting saliva into the mouth, which aids in digestion. There are 3 major paired salivary glands: the sublingual, submandibular, and parotid glands. Salivary Glands: Anatomy of the mosquito.
  • Mosquito bites a human host, inoculating virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology into keratinocytes Keratinocytes Epidermal cells which synthesize keratin and undergo characteristic changes as they move upward from the basal layers of the epidermis to the cornified (horny) layer of the skin. Successive stages of differentiation of the keratinocytes forming the epidermal layers are basal cell, spinous or prickle cell, and the granular cell. Skin: Structure and Functions.
  • The virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology moves to the lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy before spreading systemically.
  • In congenital Congenital Chorioretinitis Zika syndrome, the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infects the neural progenitor cells of the fetus.

Clinical Presentation

Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infection in adults

  • Incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period: 3–14 days
  • The majority of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship remain asymptomatic after the incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period.
  • If symptomatic, the findings are nonspecific: 
    • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
    • Arthralgia Arthralgia Pain in the joint. Rheumatic Fever
    • Myalgia Myalgia Painful sensation in the muscles. Ion Channel Myopathy
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Pruritic rash Rash Rocky Mountain Spotted Fever
    • Non-exudative conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis
  • Potential complications:
    • Guillain-BarrĂ© syndrome Guillain-BarrĂ© syndrome Guillain-BarrĂ© syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Guillain-BarrĂ© Syndrome
    • Meningoencephalitis Meningoencephalitis Encephalitis
    • Transverse myelitis Transverse myelitis Inflammation which extends horizontally across the spinal cord, believed to be immune-mediated and triggered by infection; associated with signs and symptoms of motor, sensory, and/or autonomic dysfunction. Mononucleosis

Congenital Congenital Chorioretinitis Zika syndrome

  • Most concerning complication of Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infection
  • Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infects the neural progenitor cells in the CNS.
  • Findings include:
    • Subcortical calcifications
    • Microcephaly Microcephaly A congenital abnormality in which the cerebrum is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (desk reference for neuroscience, 2nd ed. ). Fetal Alcohol Spectrum Disorder
    • Ventriculomegaly Ventriculomegaly Hydrocephalus in Children
    • Ocular defects 
    • Spasticity Spasticity Spinal Disk Herniation
    • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures

Related videos

8:16
Arboviruses – Flaviviruses
Zika virus rash

A rash Rash Rocky Mountain Spotted Fever on the back due to zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology infection.

Image: “Epidemiologic investigation of a family cluster of imported ZIKV cases in Guangdong, China: probable human-to-human transmission” by Yingxian Yin, et al AL Amyloidosis. License: CC BY 4.0
Microcephaly

Microcephaly Microcephaly A congenital abnormality in which the cerebrum is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (desk reference for neuroscience, 2nd ed. ). Fetal Alcohol Spectrum Disorder in a baby due to zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology.

Image: “ Microcephaly Microcephaly A congenital abnormality in which the cerebrum is underdeveloped, the fontanels close prematurely, and, as a result, the head is small. (desk reference for neuroscience, 2nd ed. ). Fetal Alcohol Spectrum Disorder” by Brar_j- Flickr. License: CC BY 2.0

Diagnosis and Management

Diagnosis

  • Specific diagnostic studies based on time since infection:
    • 0‒14 days after infection: PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) of blood or urine Urine Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the urethra. Bowen Disease and Erythroplasia of Queyrat samples to detect Zika RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure
    • > 14 days after infection: serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus (for antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions against Zika)
  • Nonspecific laboratory abnormalities: 
    • Leukopenia
    • Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia
    • Elevated CRP and erythrocyte sedimentation rate Erythrocyte Sedimentation Rate Soft Tissue Abscess ( ESR ESR Soft Tissue Abscess)
  • Perform PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) or serologies to rule out coinfection with dengue Dengue An acute febrile disease transmitted by the bite of aedes mosquitoes infected with dengue virus. It is self-limiting and characterized by fever, myalgia, headache, and rash. Severe dengue is a more virulent form of dengue. Dengue Virus or yellow fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology.

Management

  • No curative therapies are available.
  • Symptomatic management:
    • Oral or IV fluids IV fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids to maintain adequate hydration
    • Acetaminophen Acetaminophen Acetaminophen is an over-the-counter nonopioid analgesic and antipyretic medication and the most commonly used analgesic worldwide. Despite the widespread use of acetaminophen, its mechanism of action is not entirely understood. Acetaminophen to decrease fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and joint pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Notify the CDC.

Comparison of Species

Table: Comparison of species
Zika virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology West Nile virus West Nile Virus West Nile virus is an enveloped, positive-sense, single-stranded RNA virus of the genus Flavivirus. Birds are the primary hosts and the disease is most often transmitted by Culex mosquitoes. Most people infected with West Nile virus are asymptomatic. Some patients develop West Nile fever (a self-limited, febrile illness) and a very small proportion of patients develop West Nile neuroinvasive disease. West Nile Virus Dengue Dengue An acute febrile disease transmitted by the bite of aedes mosquitoes infected with dengue virus. It is self-limiting and characterized by fever, myalgia, headache, and rash. Severe dengue is a more virulent form of dengue. Dengue Virus virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
Characteristics
Transmission
  • Aedes mosquitoes
  • Transplacental
  • Sexual
 Culex mosquitoes Aedes mosquitoes
Clinical
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Rash Rash Rocky Mountain Spotted Fever
  • Myalgias Myalgias Painful sensation in the muscles. Tick-borne Encephalitis Virus
  • Conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Rash Rash Rocky Mountain Spotted Fever
  • Myalgias Myalgias Painful sensation in the muscles. Tick-borne Encephalitis Virus
  • Encephalitis Encephalitis Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. Encephalitis
  • Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • “Breakbone” pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
  • Rash Rash Rocky Mountain Spotted Fever
  • Hemorrhage
  • Shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
Diagnosis
  • Clinical
  • Travel history
  • Serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus
  • PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR)
  • Clinical
  • Travel history
  • Serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus
  • PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR)
  • Clinical
  • Travel history
  • Cell cultures Cultures Klebsiella
  • ELISA ELISA An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed. St. Louis Encephalitis Virus
  • RT-PCR RT-PCR A variation of the pcr technique in which cDNA is made from RNA via reverse transcription. The resultant cDNA is then amplified using standard pcr protocols. Polymerase Chain Reaction (PCR)
  • Serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus
Management Symptomatic treatment
Prevention
  • Mosquito control
  • Personal protection with insect repellants and protective clothing
  • Mosquito control
  • Personal protection with insect repellants and protective clothing
  • Mosquito control
  • Vaccine Vaccine Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccination

Differential Diagnosis

The following conditions are differential diagnoses for congenital Congenital Chorioretinitis Zika syndrome:

  • Congenital toxoplasmosis Congenital toxoplasmosis Prenatal protozoal infection with toxoplasma gondii which is associated with injury to the developing fetal nervous system. The severity of this condition is related to the stage of pregnancy during which the infection occurs; first trimester infections are associated with a greater degree of neurologic dysfunction. Clinical features include hydrocephalus; microcephaly; deafness; cerebral calcifications; seizures; and psychomotor retardation. Signs of a systemic infection may also be present at birth, including fever, rash, and hepatosplenomegaly. Toxoplasma/Toxoplasmosis: a congenital Congenital Chorioretinitis TORCHES infection caused by the protozoa Protozoa Nitroimidazoles Toxoplasma Toxoplasma Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host’s immune status. Toxoplasma/Toxoplasmosis gondii. Toxoplasmosis Toxoplasmosis Toxoplasmosis is an infectious disease caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. Felines are the definitive host, but transmission to humans can occur through contact with cat feces or the consumption of contaminated foods. The clinical presentation and complications depend on the host’s immune status. Toxoplasma/Toxoplasmosis is most commonly transmitted by the ingestion of undercooked pork, but can also be transmitted after contact with cat feces. Congenital toxoplasmosis Congenital toxoplasmosis Prenatal protozoal infection with toxoplasma gondii which is associated with injury to the developing fetal nervous system. The severity of this condition is related to the stage of pregnancy during which the infection occurs; first trimester infections are associated with a greater degree of neurologic dysfunction. Clinical features include hydrocephalus; microcephaly; deafness; cerebral calcifications; seizures; and psychomotor retardation. Signs of a systemic infection may also be present at birth, including fever, rash, and hepatosplenomegaly. Toxoplasma/Toxoplasmosis presents with the triad of chorioretinitis Chorioretinitis Chorioretinitis is the inflammation of the posterior segment of the eye, including the choroid and the retina. The condition is usually caused by infections, the most common of which is toxoplasmosis. Some of these infections can affect the fetus in utero and present as congenital abnormalities. Chorioretinitis, hydrocephalus Hydrocephalus Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, intracranial. Subarachnoid Hemorrhage, and diffuse intracranial (rather than subcortical) calcifications. Diagnosis is made with serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus. Treatment is using pyrimethamine Pyrimethamine One of the folic acid antagonists that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis. Antimalarial Drugs– sulfadiazine Sulfadiazine One of the short-acting sulfonamides used in combination with pyrimethamine to treat toxoplasmosis in patients with acquired immunodeficiency syndrome and in newborns with congenital infections. Sulfonamides and Trimethoprim. 
  • Congenital cytomegalovirus Congenital Cytomegalovirus Congenital TORCH Infections infection: a congenital Congenital Chorioretinitis TORCHES infection caused by cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus, also known as human herpesvirus 5 ( HHV-5 HHV-5 CMV is a ubiquitous double-stranded DNA virus belonging to the herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus). Cytomegalovirus Cytomegalovirus CMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis. Cytomegalovirus is transmitted by urine Urine Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the urethra. Bowen Disease and Erythroplasia of Queyrat, blood, saliva Saliva The clear, viscous fluid secreted by the salivary glands and mucous glands of the mouth. It contains mucins, water, organic salts, and ptyalin. Salivary Glands: Anatomy, sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria, and organ transplantation Organ Transplantation Transplantation is a procedure that involves the removal of an organ or living tissue and placing it into a different part of the body or into a different person. Organ transplantations have become the therapeutic option of choice for many individuals with end-stage organ failure. Organ Transplantation. Congenital cytomegalovirus Congenital Cytomegalovirus Congenital TORCH Infections presents with hearing loss Hearing loss Hearing loss, also known as hearing impairment, is any degree of impairment in the ability to apprehend sound as determined by audiometry to be below normal hearing thresholds. Clinical presentation may occur at birth or as a gradual loss of hearing with age, including a short-term or sudden loss at any point. Hearing Loss, seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures, “blueberry muffin” rash Rash Rocky Mountain Spotted Fever, and periventricular (rather than subcortical) calcifications. Diagnosis is made by serology Serology The study of serum, especially of antigen-antibody reactions in vitro. Yellow Fever Virus or PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR). Treatment is using ganciclovir Ganciclovir An acyclovir analog that is a potent inhibitor of the herpesvirus family including cytomegalovirus. Ganciclovir is used to treat complications from aids-associated cytomegalovirus infections. Antivirals for Herpes Virus or valganciclovir. 
  • Congenital Congenital Chorioretinitis herpes infection: a congenital Congenital Chorioretinitis TORCHES infection caused by herpes simplex Herpes Simplex A group of acute infections caused by herpes simplex virus type 1 or type 2 that is characterized by the development of one or more small fluid-filled vesicles with a raised erythematous base on the skin or mucous membrane. It occurs as a primary infection or recurs due to a reactivation of a latent infection. Congenital TORCH Infections virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology ( HSV HSV Herpes simplex virus (HSV) is a double-stranded DNA virus belonging to the family Herpesviridae. Herpes simplex virus commonly causes recurrent infections involving the skin and mucosal surfaces, including the mouth, lips, eyes, and genitals. Herpes Simplex Virus 1 and 2) 2. Herpes simplex Herpes Simplex A group of acute infections caused by herpes simplex virus type 1 or type 2 that is characterized by the development of one or more small fluid-filled vesicles with a raised erythematous base on the skin or mucous membrane. It occurs as a primary infection or recurs due to a reactivation of a latent infection. Congenital TORCH Infections virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology is transmitted transvaginally from an infected mother to the fetus while the fetus is in contact with lesions in the birth canal Birth canal Pelvis: Anatomy. Congenital Congenital Chorioretinitis herpes infection presents with skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions and mucous membrane Mucous membrane An epithelium with mucus-secreting cells, such as goblet cells. It forms the lining of many body cavities, such as the digestive tract, the respiratory tract, and the reproductive tract. Mucosa, rich in blood and lymph vessels, comprises an inner epithelium, a middle layer (lamina propria) of loose connective tissue, and an outer layer (muscularis mucosae) of smooth muscle cells that separates the mucosa from submucosa. Barrett’s Esophagus vesicles Vesicles Female Genitourinary Examination similar to those seen in adults. Congenital Congenital Chorioretinitis herpes infection can also be disseminated and involve multiple organs. Diagnosis is confirmed using viral PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR), and treatment includes acyclovir Acyclovir A guanosine analog that acts as an antimetabolite. Viruses are especially susceptible. Used especially against herpes. Herpes Zoster (Shingles).

References

  1. LaBeaud, A.D. (2021). Zika virus infection: An overview. UpToDate. https://www.uptodate.com/contents/Zika-virus-infection-an-overview
  2. Nielsen-Saines, K. (2021). Congenital Zika virus infection: Clinical features, evaluation, and management of the neonate. UpToDate. https://www.uptodate.com/contents/congenital-Zika-virus-infection-clinical-features-evaluation-and-management-of-the-neonate
  3. Navalkele, B.D. (2020). Zika virus: Background, pathophysiology, epidemiology. Medscape. https://emedicine.medscape.com/article/2500035-overview
  4. Vouga M, et al. (2018). Updated Zika virus recommendations are needed. Lancet. 392(10150), 818–819. https://pubmed.ncbi.nlm.nih.gov/30146329/
  5. Moreira-Soto, A., et al. (2018). Exhaustive TORCH pathogen diagnostics corroborate Zika virus etiology of congenital malformations in Northeastern Brazil. mSphere, 3(4) https://pubmed.ncbi.nlm.nih.gov/30089647/
  6. Shehu, N.Y., et al. (2018). Pathogenesis, diagnostic challenges and treatment of Zika virus disease in resource-limited settings. Niger Postgrad Med J. 25(2), 67–72. https://pubmed.ncbi.nlm.nih.gov/30027916/
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