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Questions and Answers
What is the primary mode of transmission for enteroviruses?
What is the primary mode of transmission for enteroviruses?
Hand-to-mouth contact.
Which group of enteroviruses is known to cause paralytic poliomyelitis?
Which group of enteroviruses is known to cause paralytic poliomyelitis?
Poliovirus.
What are common symptoms of enterovirus infections in children?
What are common symptoms of enterovirus infections in children?
Respiratory infections, conjunctivitis, and hand-foot-mouth disease (HFMD).
How does the virulence of enterovirus compare to poliovirus?
How does the virulence of enterovirus compare to poliovirus?
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What age group is particularly at risk for severe disease when infected with Enterovirus 71?
What age group is particularly at risk for severe disease when infected with Enterovirus 71?
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Which enterovirus can lead to aseptic meningitis among other conditions?
Which enterovirus can lead to aseptic meningitis among other conditions?
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What impact does damage to anterior horn cells have on muscle function?
What impact does damage to anterior horn cells have on muscle function?
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In what regions have outbreaks of Enterovirus 71 been previously reported?
In what regions have outbreaks of Enterovirus 71 been previously reported?
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What are the key clinical features commonly associated with aseptic meningitis?
What are the key clinical features commonly associated with aseptic meningitis?
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Which viruses are most commonly responsible for viral encephalitis?
Which viruses are most commonly responsible for viral encephalitis?
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What differentiates encephalitis from meningitis?
What differentiates encephalitis from meningitis?
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Identify the typical CSF findings in cases of viral meningitis.
Identify the typical CSF findings in cases of viral meningitis.
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What condition is referred to when there is inflammation of both the brain and spinal cord?
What condition is referred to when there is inflammation of both the brain and spinal cord?
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What is acute flaccid paralysis and what can cause it?
What is acute flaccid paralysis and what can cause it?
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What is the significance of mononuclear pleocytosis in aseptic meningitis?
What is the significance of mononuclear pleocytosis in aseptic meningitis?
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List two common symptoms of viral encephalitis.
List two common symptoms of viral encephalitis.
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What is the primary mode of transmission for Japanese encephalitis virus?
What is the primary mode of transmission for Japanese encephalitis virus?
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Which animals are considered dead-end hosts for Japanese encephalitis virus?
Which animals are considered dead-end hosts for Japanese encephalitis virus?
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What are some clinical signs of Japanese encephalitis?
What are some clinical signs of Japanese encephalitis?
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What hypothesis suggests how JEV enters the central nervous system from the blood?
What hypothesis suggests how JEV enters the central nervous system from the blood?
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What percentage of Japanese encephalitis survivors might experience neuropsychiatric sequelae?
What percentage of Japanese encephalitis survivors might experience neuropsychiatric sequelae?
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What factors influence the overflow of JEV into domestic animals during the transmission cycle?
What factors influence the overflow of JEV into domestic animals during the transmission cycle?
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What can be a consequence of in utero infection by Japanese encephalitis virus?
What can be a consequence of in utero infection by Japanese encephalitis virus?
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What destruction occurs in neurons due to West Nile Virus (WNV)?
What destruction occurs in neurons due to West Nile Virus (WNV)?
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What percentage of hospitalized patients with Japanese Encephalitis (JE) die?
What percentage of hospitalized patients with Japanese Encephalitis (JE) die?
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What are some possible neurologic sequelae in survivors of JE?
What are some possible neurologic sequelae in survivors of JE?
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What is the primary cause of herpes simplex encephalitis?
What is the primary cause of herpes simplex encephalitis?
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How does rabies enter the central nervous system (CNS)?
How does rabies enter the central nervous system (CNS)?
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What are Negri bodies, and in which viral infection are they found?
What are Negri bodies, and in which viral infection are they found?
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Describe the prodromal phase of rabies infection.
Describe the prodromal phase of rabies infection.
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What is the mortality rate for neonatal herpes simplex encephalitis?
What is the mortality rate for neonatal herpes simplex encephalitis?
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What factors can influence the severity of chickenpox and shingles caused by Varicella Zoster Virus (VZV)?
What factors can influence the severity of chickenpox and shingles caused by Varicella Zoster Virus (VZV)?
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What are the main neurocognitive disorders associated with HIV infection?
What are the main neurocognitive disorders associated with HIV infection?
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How does HIV affect the blood-brain barrier?
How does HIV affect the blood-brain barrier?
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What role do neurotoxic viral proteins play in HIV-associated neurocognitive disorders?
What role do neurotoxic viral proteins play in HIV-associated neurocognitive disorders?
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What is the effect of sustained viral replication on brain tissue?
What is the effect of sustained viral replication on brain tissue?
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Why is the CNS considered a compartmentalized viral reservoir in some HIV patients?
Why is the CNS considered a compartmentalized viral reservoir in some HIV patients?
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Study Notes
CNS Viral Infections
- Common CNS viral infections include meningitis, encephalitis, myelitis, and paralysis.
- Aseptic meningitis is a form of meningitis not caused by bacteria.
- The most common cause of aseptic meningitis is viral infection, with enteroviruses being the most frequent culprits.
- Enteroviruses can cause respiratory infections, conjunctivitis and hand-foot-mouth disease (HFMD).
- Encephalitis is an inflammation of the brain.
- Myelitis is an inflammation of the spinal cord.
- Encephalitis with meningitis is called meningoencephalitis.
- Acute flaccid paralysis (AFP) is characterized by sudden weakness in one or more limbs, which can be caused by various viral infections, including poliovirus, enterovirus 71, and other enteroviruses.
- Anterior horn cells in the spinal cord contain motor neurons, which are crucial for transmitting brain-generated movement commands to muscles. Damage to these cells affects muscle function.
Enteroviruses
- Enteroviruses are non-enveloped, single-stranded RNA viruses (ssRNA) belonging to the Picornaviridae family.
- There are at least 72 serotypes of enteroviruses.
- Enteroviruses are transmitted via hand-to-mouth contact.
- Transmission occurs through saliva, nasal mucous, or sputum from infected individuals.
Poliovirus
- Paralytic poliomyelitis is a rare but potentially serious complication of poliovirus infection that causes paralysis.
- Poliovirus can also cause aseptic meningitis and febrile illness (fever).
Coxsackievirus
- Coxsackievirus group A can cause aseptic meningitis.
- Coxsackievirus group B can cause aseptic meningitis and encephalitis.
Echovirus
- Echoviruses can cause aseptic meningitis.
Enterovirus
- Enteroviruses can cause meningitis.
Enterovirus 71
- Enterovirus 71 usually causes mild illness in adults and children.
- Outbreaks of EV71 are associated with severe disease, including meningitis and encephalitis, particularly in young children under 5 years old.
- EV71 has been reported in Asia for many years and occasionally in Australia.
Arboviruses
- Arboviruses are viruses spread through the bites of infected arthropods, primarily mosquitoes and ticks.
- Arboviruses causing encephalitis include:
- Eastern equine encephalitis
- Western equine encephalitis
- La Crosse encephalitis
- Japanese encephalitis virus (JEV)
- Certain arboviruses are transmitted by mosquitos and can affect both humans and animals.
Japanese Encephalitis Virus (JEV)
- JEV is a mosquito-borne flavivirus that affects the central nervous system.
- JEV is transmitted naturally between aquatic birds by Culex mosquitoes.
- During the rainy season, an increase in mosquitos allows the virus to spread to other animals, including pigs, and then to humans.
- While humans are not a significant source of virus transmission, they can be considered "dead-end hosts."
- JEV can cause a range of symptoms, from fever and headache to coma and death.
- About 1 in 25 to 1 in 1000 infected people develop symptomatic disease.
- About 30% of hospitalized patients with JE die.
- Neurologic sequelae occur in about half of survivors, with about half of those experiencing difficulties such as learning disabilities, behavioral problems, and subtle neurologic signs.
- The clinical course of JEV infection is characterized by:
- Acute encephalitis: Symptoms include headache, high fever, stiff neck, and stupor. The disease may progress to paralysis, seizures, convulsions, coma, and death.
- Neuropsychiatric sequelae: These occur in 45-70% of survivors.
- In utero infection is possible, leading to abortion of the fetus.
Herpes Simplex Virus (HSV)
- HSV is an enveloped, double-stranded DNA virus (dsDNA) belonging to the Herpesviridae family.
- HSV can cause a variety of infections, including:
- Acute gingivostomatitis
- Herpes labialis (cold sores)
- Herpetic whitlow (infection of the finger)
- Ocular herpes (infection of the eye)
- Genital herpes
- Neonatal herpes
- Meningitis
- Encephalitis
- HSV encephalitis is responsible for about 10% of all encephalitis cases.
- About 30% of HSV encephalitis cases result from an initial infection, while the majority are caused by reactivation of a prior infection.
- HSV encephalitis can manifest as neonatal HSVE (with a >25% mortality rate) or focal disease following HSV reactivation (with a 70% mortality rate in the absence of treatment).
Varicella Zoster Virus (VZV)
- VZV is an enveloped, double-stranded DNA virus (dsDNA) belonging to the Herpesviridae family.
- VZV causes varicella (chickenpox) during primary infection, typically a self-limiting illness in children. However, it can cause significant morbidity and mortality in other age groups and immunocompromised individuals.
- VZV reactivation leads to herpes zoster (shingles), which primarily affects the elderly or immunocompromised.
- VZV can also cause encephalitis in immunocompromised patients.
Rabies
- Rabies is an enveloped, single-stranded RNA virus (-) ssRNA belonging to the Rhabdoviridae (Lyssavirus) family.
- Rabies is spread through the bite of an infected animal, often through the salivary contamination of mucous membranes or aerosols.
- The virus replicates in muscle tissue and then moves along peripheral nerves into the central nervous system (CNS) through retrograde axonal transport.
- Once the virus enters the nerves, it becomes inaccessible to the host's immune defenses.
- The infection cycle is completed when the virus replicates in the salivary glands.
- The incubation period for rabies can range from weeks to up to two years, with shorter periods in children and for bites to the head or neck.
- Clinical phases of rabies include:
- Prodromal phase: Fever, nausea, vomiting, headache, fatigue, pain, burning, tingling sensations at the site of the wound.
- Furious phase: Agitation, disorientation, seizures, twitching, hydrophobia.
- Dumb phase: Paralysis, disorientation, stupor.
- Coma phase: Ultimately leading to death in almost all cases.
- Post-exposure vaccination with recombinant antigen, human antisera, or monoclonal antibodies (Mabs) can provide protection if administered before the onset of symptoms.
HIV and the Nervous System
- HIV enters the nervous system early in infection and may cause symptoms immediately or later in life.
- HIV easily crosses the blood-brain barrier.
- Primary HIV disease can lead to:
- AIDS Dementia Complex (brain)
- Vacuolar Myelopathy (spinal cord)
- Peripheral Neuropathy (nerve)
- Meningitis (acute or chronic)
- Sustained viral replication and a high viral load are associated with brain tissue inflammation, permanent cell death, and HIV-associated neurocognitive disorders (HAND).
- HIV-1 variants in the cerebrospinal fluid (CSF) may not be present in the blood, suggesting that the CNS may be a compartmentalized viral reservoir.
HIV-associated Neurocognitive Disorders (HAND)
- HAND encompass a spectrum of neurocognitive impairments associated with HIV infection, ranging from mild cognitive impairment to severe dementia.
- The neuropathogenic mechanisms contributing to HAND include:
- Release of neurotoxic viral proteins from HIV-infected macrophages and microglial cells that trigger astrocyte activation and increased glutamate release.
- Reduced glutamate uptake, leading to elevated extracellular glutamate levels and neuronal bioenergetic disturbances. This can lead to aberrant synapto-dendritic pruning and neuronal injury.
- Systemic inflammation and microbial translocation products activate microglia, increasing the production of chemokines and cytokines that contribute to neuronal injury.
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Description
This quiz covers essential information about common CNS viral infections such as meningitis, encephalitis, myelitis, and acute flaccid paralysis. It highlights the role of enteroviruses, including their effects on the body and potential complications. Test your knowledge on the causes and characteristics of these viral infections.
