B3 measles

Question 1

What happens in an acute symptomatic infection?

Answer 1

→ Infection of a small number of cells, followed by multiple cycles of viral replication.

Question 2

How does an acute infection spread?

Answer 2

It can stay local or spread systemically.

Question 3

What are the outcomes of an acute symptomatic infection?

Answer 3

Clearance by the immune response and recovery, or progression to chronic/latent infection or death.

Question 4

What is the typical duration of an acute symptomatic infection?

Answer 4

Days to weeks.

Question 5

How contagious is measles?

Answer 5

One of the most contagious diseases.

Question 6

What is the mortality rate of measles in developed countries?

Answer 6

→ 0.1%.

Question 7

What is the mortality rate of measles in developing countries?

Answer 7

→ 5-10%.

Question 8

How are paramyxoviruses transmitted?

Answer 8

Readily via the respiratory route.

Question 9

What are the two patterns of infection caused by paramyxoviruses?

Answer 9

1. Localised respiratory infections (e.g., RSV, hMPV). 2. Systemic infections (e.g., measles, mumps).

Question 10

Why are paramyxoviruses dangerous for infants?

Answer 10

Localised respiratory infections are trivial in adults but can be severe in infants and children.

Question 11

How is measles transmitted?

Answer 11

Aerosol droplets.

Question 12

Where does measles initially replicate?

Answer 12

Upper respiratory tract epithelium.

Question 13

What happens in primary viraemia?

Answer 13

Virus is mainly associated with lymphocytes and macrophages, with little free virus in the blood.

Question 14

Where does measles replicate after primary viraemia?

Answer 14

Lymphoid tissues (spleen, lymph nodes, appendix, tonsils).

Question 15

What happens in secondary viraemia?

Answer 15

Virus spreads to organs such as skin, conjunctiva, liver, kidney, lungs, and gut.

Question 16

What causes the characteristic measles rash?

Answer 16

Immune response to virus-infected endothelial cells.

Question 17

What are the main symptoms of measles?

Answer 17

Fever, cough, runny nose (coryza), conjunctivitis, maculopapular rash.

Question 18

What are Koplik’s spots?

Answer 18

White spots inside the mouth, a hallmark of measles.

Question 19

What is giant cell pneumonia?

Answer 19

Severe pneumonia caused by syncytia formation, often fatal in immunocompromised patients.

Question 20

How does measles suppress the immune system?

Answer 20

Infects and depletes memory B and T cells, causing “immune amnesia” and increased risk of secondary infections.

Question 21

What bacterial infections are common after measles?

Answer 21

Otitis media (ear infection) and pneumonia (~15% of cases).

Question 22

What is the leading cause of measles-related deaths?

Answer 22

Pneumonia (60% of deaths).

Question 23

What is measles encephalitis?

Answer 23

Inflammation of the brain, occurring in 1 in 1000 cases, often causing neural damage.

Question 24

What is SSPE?

Answer 24

A rare, fatal, slow-progressing CNS disease occurring years after measles infection.

Question 25

Who is at highest risk of SSPE?

Answer 25

Males and those infected with measles under 2 years old.

Question 26

What causes SSPE?

Answer 26

Persistent defective (non-infectious) measles virus in the brain, triggering a hyperimmune response.

Question 27

What type of genome does measles have?

Answer 27

Negative-sense single-stranded RNA (-ve ssRNA).

Question 28

What proteins are important for measles virus entry?

Answer 28

H protein (docking) and F protein (fusion).

Question 29

What cellular receptors does measles target?

Answer 29

CD46/CD150 on lymphocytes and epithelial cells.

Question 30

What is the function of RdRp in measles?

Answer 30

Transcribes the genome into mRNA and replicates it into a full-length positive-sense copy.

Question 31

How does measles virus assemble and release?

Answer 31

F & H proteins move to the cell membrane, M protein associates with RNP, leading to viral release.

Question 32

What is syncytia formation, and why is it important?

Answer 32

Measles virus induces fusion of infected cells, forming multinucleated giant cells.

Question 33

What is more important for clearing measles: T cells or antibodies?

Answer 33

→ T cells.

Question 34

What causes the symptoms of measles?

Answer 34

Immune response rather than direct viral damage (e.g., cytokines cause fever, T cells attack infected endothelial cells causing rash).

Question 35

Why is the absence of a rash a bad sign in measles?

Answer 35

→ Indicates poor T cell response and poor prognosis.

Question 36

What is required for lifelong immunity to measles?

Answer 36

A strong antibody response (IgG) prevents reinfection.

Question 37

Why is measles vaccine effective?

Answer 37

Only one serotype, live attenuated vaccine, induces a strong immune response.

Question 38

What does the MMR vaccine protect against?

Answer 38

Measles, mumps, and rubella.

Question 39

hy are two doses of measles vaccine given?

Answer 39

First dose may be neutralised by maternal antibodies; second dose ensures full immunity.

Question 40

Why is high vaccine uptake essential?

Answer 40

To achieve herd immunity and break the chain of transmission.

Question 41

What are examples of localised acute infections caused by paramyxoviruses?

Answer 41

Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV).

Question 42

Why does measles have little free virus in the blood during primary viraemia?

Answer 42

The virus is mostly associated with immune cells like lymphocytes and macrophages.

Question 43

What does “gradient of transcripts” mean in measles virus transcription?

Answer 43

RdRp transcribes genes in a sequential manner, leading to higher levels of 5’ genes and lower levels of 3’ genes.