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Questions and Answers
How does measles infection lead to transient suppression of cell-mediated immunity, potentially exacerbating other intracellular infections such as Mycobacterium tuberculosis?
How does measles infection lead to transient suppression of cell-mediated immunity, potentially exacerbating other intracellular infections such as Mycobacterium tuberculosis?
- By inducing a cytokine storm that exhausts T cells and reduces their responsiveness to other pathogens.
- By directly lysing macrophages and dendritic cells, impairing antigen presentation to T cells.
- By downregulating the expression of MHC class I molecules on infected cells, preventing T cell recognition.
- By temporarily depleting naive T cells and skewing the immune response towards humoral immunity. (correct)
How does the measles virus spread within the host following initial infection of respiratory epithelial cells?
How does the measles virus spread within the host following initial infection of respiratory epithelial cells?
- Utilizes monocytes and lymphocytes for dissemination through the lymphatic system and via cell-associated viremia. (correct)
- Remains localized in the respiratory tract, causing damage that facilitates secondary bacterial infections.
- Directly invades the bloodstream, causing a rapid systemic infection without lymphatic involvement.
- Primarily infects neurons, leading to neurological symptoms early in the prodromal phase.
Which of the following mechanisms explains how subacute sclerosing panencephalitis (SSPE) develops years after acute measles infection?
Which of the following mechanisms explains how subacute sclerosing panencephalitis (SSPE) develops years after acute measles infection?
- Reactivation of latent measles virus in neuronal tissues due to waning immunity.
- Autoimmune response triggered by measles antigens that cross-react with brain proteins.
- Initial misdiagnosis of measles leading to incomplete treatment allowing the virus to establish a chronic infection.
- Persistent infection with a defective measles variant that replicates poorly and remains cell-associated, leading to neurological damage. (correct)
In a patient with suspected measles presenting with atypical symptoms and no Koplik spots, which historical factor would most strongly suggest a diagnosis of atypical measles?
In a patient with suspected measles presenting with atypical symptoms and no Koplik spots, which historical factor would most strongly suggest a diagnosis of atypical measles?
Why is the live attenuated measles vaccine contraindicated for immunocompromised individuals and pregnant women?
Why is the live attenuated measles vaccine contraindicated for immunocompromised individuals and pregnant women?
How does measles infection lead to Koplik spots?
How does measles infection lead to Koplik spots?
What is the primary mechanism by which measles causes pneumonia?
What is the primary mechanism by which measles causes pneumonia?
What is the role of hemagglutinin (HA) and fusion (F) proteins in the pathogenesis of measles?
What is the role of hemagglutinin (HA) and fusion (F) proteins in the pathogenesis of measles?
A clinician suspects measles encephalitis in a patient presenting with neurological symptoms following a recent measles infection. Which diagnostic test would best differentiate between direct viral infection of neurons and post-infectious encephalitis?
A clinician suspects measles encephalitis in a patient presenting with neurological symptoms following a recent measles infection. Which diagnostic test would best differentiate between direct viral infection of neurons and post-infectious encephalitis?
What is the most appropriate strategy for controlling measles outbreaks in populations with low vaccination rates?
What is the most appropriate strategy for controlling measles outbreaks in populations with low vaccination rates?
Flashcards
Measles Virus
Measles Virus
A member of the Paramyxoviridae family; negative-sense, single-stranded RNA virus transmitted via respiratory droplets that causes fever, cough, and a characteristic rash.
Koplik Spots
Koplik Spots
Bright red lesions with a white central dot, located on buccal mucosa, virtually diagnostic of measles.
Measles-induced Immune Suppression
Measles-induced Immune Suppression
Suppresses cell-mediated immunity against other intracellular pathogens such as Mycobacterium tuberculosis.
Subacute Sclerosing Panencephalitis (SSPE)
Subacute Sclerosing Panencephalitis (SSPE)
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Measles Vaccine
Measles Vaccine
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Measles Transmission
Measles Transmission
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Measles Prodromal Phase
Measles Prodromal Phase
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Measles-Associated Encephalitis
Measles-Associated Encephalitis
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Atypical Measles
Atypical Measles
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Study Notes
- Measles is part of the Paramyxoviridae family and Morbillivirus genus.
- The virus is a negative-sense, single-stranded RNA virus with a helical nucleocapsid and pleomorphic envelope.
- It has hemagglutinin (HA) and fusion (F) envelope spikes, the latter enabling self-fusion and hemolytic activity.
- The measles virus has a single serotype.
Transmission
- Measles is transmitted via respiratory droplets produced by coughing and sneezing.
- Transmission occurs during the prodromal phase and for a few days after the rash appears.
- After replicating locally in respiratory tract epithelial cells, the virus infects monocytes and lymphocytes.
- It then spreads through the lymphatic system and via cell-associated viremia.
- Measles infection can transiently suppress cell-mediated immunity against other intracellular pathogens like Mycobacterium tuberculosis.
Prodromal Phase
- The first stage involves high fever, coryza (runny nose), conjunctivitis, cough, and photophobia.
- Koplik spots (bright red lesions with a white central dot on the buccal mucosa) are virtually diagnostic.
- A maculopapular rash appears on the face, spreading down to the lower extremities, including palms and soles.
- Several days later, the rash turns brownish.
- Recovery follows the rash in most patients, resulting in lifelong immunity.
Complications
- Complications include death from pneumonia, diarrhea, or encephalitis.
- Permanent sequelae (e.g., deafness, mental retardation) occur in 40% of cases.
- Otitis media is a common complication.
- Subacute sclerosing panencephalitis (SSPE), a rare and fatal disease, can occur years after acute infection.
- During pregnancy, measles increases the risk of stillbirth, but not congenital abnormalities.
- Encephalitis occurs in 1 per 1,000 cases, with a 10% mortality rate.
Encephalitis
- Measles can cause encephalitis through direct neuronal infection or post-infectious (immune-mediated) means.
- Subacute Sclerosing Panencephalitis (SSPE) is caused by a defective measles virus variant.
- This leads to poor replication, cell association, and neurological symptoms years post-infection.
- T-cell deficient children with measles may have atypical presentations, like giant cell pneumonia with opportunistic infections.
- Both primary measles pneumonia and secondary bacterial pneumonia are possible.
- Atypical measles, occurring in those who received the killed vaccine, presents with an atypical rash and no Koplik spots
Diagnosis
- Clinical manifestations are typically so characteristic that laboratory tests are often unnecessary.
- Confirmation can be done by RT-PCR on respiratory secretions, urine, blood, or brain tissue.
- A greater-than-fourfold rise in antibody titer (ELISA) can confirm the diagnosis in difficult cases.
- Pathological effects include multinucleated giant cells with cytoplasmic inclusion bodies in respiratory samples.
Treatment and Prevention
- There is no specific antiviral treatment for measles.
- Prevention involves a live attenuated measles vaccine given after 12 months of age.
- It is administered as part of the MMR (Measles, Mumps, Rubella) vaccine, often with the varicella vaccine.
- A booster dose is recommended.
- Due to the live virus, the vaccine is contraindicated for immunocompromised individuals and pregnant women.
Epidemiology
- Measles occurs worldwide, usually in outbreaks every 2-3 years when susceptibility is high.
- Many cases occur in unvaccinated preschool-aged children in large urban areas.
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