Viral Infections: Measles

Question 1

Describe the general characteristics of Acute (Transient) Viral Infections

Answer 1

> Structurally heterogenous viruses

> All elicit EFFECTIVE immune response to clear the infection

> Some can re-infect with different genetic variant (e.g. Influenza)

> Some cannot re-infect the same person (because of only ONE SEROTYPE)

Question 2

Mumps is also known as

Answer 2

Rubeola

Question 3

Measles has ___ RNA and is part of the ___ family

Answer 3

ssRNA; Paramyxovirus

Question 4

What is the leading cause of vaccine-preventable death and why?

Answer 4

Measles / Rubeola is the leading cause of vaccine-preventable DEATH AND ILLNESS because of poor sanitation developing countries.

Question 5

Presentation range of measles

Answer 5

Mild/self-limiting to severe

Question 6

When can measles be severe?

Answer 6

If with T-cell defects such as HIV infections and leukemias

Question 7

How to diagnose measles?

Answer 7

> Clinical

> Serology

> Antigen testing

Question 8

How many serotypes does measles have?

Answer 8

Only ONE (meaning, you can catch it only once)

Question 9

Mode of transmission of measles

Answer 9

Respiratory Droplets

Question 10

How does viral hemagglutinin of measles infect cells?

Answer 10

Binds to 3 proteins to enter the cells:

> CD46 - on all NUCLEATED cells

> SLAM (Signaling Lymphocyte Activation Molecule) - on cells of IMMUNE system

> Nectin 4 - on basal surface of ALL EPITHELIAL cells

Question 11

Measles virus replicates in what kinds of cells?

Answer 11

> Epithelial cells

> Leukocytes

Question 12

Discuss how measles virus enters the body. What organs does it affect?

Answer 12

Enter the respiratory tract –> disseminate in lymphoid tissues –> result to viremia (virus spreads throughout the body)

Organs affected: 
> Conjunctiva
> Skin
> Respiratory tract (Pneumonia)
> Urinary tract
> Small blood vessels
> Lymphatic system
> CNS

Question 13

What is the cause of rashes in measles? How does the rashes appear like and what parts of the body can it be seen in?

Answer 13

> Due to INTACT T-cell immunity (rash is less frequent in people with deficiencies in cell-mediated immunity)

> Blotchy, reddish brown –> Face, Trunk, Proximal extremities

Question 14

What are the manifestations of measles in malnourished children?

Answer 14

SEVERE such as:

> Croup
> Pneumonia
> Diarrhea
> Protein losing enteropathy
> Keratitis
> Encephalitis
> Hemorrhagic rashes (Black measles)

Question 15

Why is preventing measles important?

Answer 15

> Important because if you get vaccinated, you are protected not just from measles, but also from other diseases

> Measles can cause TRANSIENT IMMUNOSUPPRESSION, resulting to secondary bacterial and viral infections

Question 16

Give examples for late complications of measles

Answer 16

> SSPE (Subacute Sclerosing Panencephalitis) - happens YEARS AFTER getting infected; Almost always fatal (CNS manifestation)

> Measles Inclusion Body Encephalitis ( in immunocompromised individuals)

Question 17

What is a CHARACTERISTIC FINDING in measles? Describe how it appears like.

Answer 17

Koplik Spots
> Ulcerated mucosal lesions in the oral cavity near opening of Stensen ducts
> On microscopy, they have necrosis, neutrophilic exudates, and neovascularization

Question 18

Describe the morphology of lymphoid tissues in measles

Answer 18

> Marked follicular hyperplasia

> Large germinal centers

> Scattered giant cells (Warthin-Finkeldey cells) –> have eosinophilic nuclear and cytoplasmic inclusion bodies; Also found in lung and sputum