Measles (V)

What virus causes measles (rubeola)?

Morbillivirus (Paryamyxoviridae), and enveloped, negative-sense ssRNA virus

What is the portal of entry for Measles virus?

Respiratory tract

What makes measles so contagious?

highly efficient respiratory droplet spread and a very high attack rate (>80% of unimmunized exposed individuals fall ill)

What are the early symptoms of measles?

Fever, sore throat, headache, cry cough, Conjunctivitis What

What are the Three C’s?

Cough, Coryza, Conjuctiva

What symptom is pathognomonic (diagnostic) for measles?

Koplik’s spots: white lesions with a red halo on the oral mucosa D

Describe the measles rash

Red, raised maculopapular lesions that start on the head and spread over the body; often fuse and later turn brown

What serious complications can measles cause?

Pneumonia, encephalitis, deafness, blindness, and SSPE

What is SSPE?

Subacute schleroing panencephalitis - a fatal, progressive CNS disease causing personality changes, memory loss, muscle spasms, blindness, and death years after infection

How does SSPE develop?

From a defective measles virion that lack capsid formation; spreads cell-to-cell in the brain via fusion

How does measles spread through the body?

Infects respiratory tract → spreads through lymph and blood → infects Conjuctiva, urinary tract, blood vessels, lymphatics, CNS, and skin

What causes most the symptoms of measles?

Cytotoxic T-cell response that kills infected cellsWho

Who is at the highest risk for severe measles?

Unimmunized children and immunocompromised patients (e.g., AIDS).

What is the incubation period for measles?

8-12 days

How is measles diagnosed?

Presence of Koplik’s spots; serological tests can confirm viral antigen

What is the treatment for measles?

Supportive care, vitamin A, antiviral ribavirin, and anti-measles antibodies

What are the measles virus virulence factors

Adhesion proteins and a fusion protein enabling cell-cell spread and antibody envasion

What vaccine prevents measles?

MMR vaccine (measles, mumps, rubella) - live attenuated virus

What is the MMR vaccine given?

First dose at 12 months; second dose at 4 years

What vaccination rate is needed for measles elimination?

=>95% two-dose coverage

Why can the measles vaccine pose a risk to immunocompromised individuals?

It is a live attenuated vaccine that can still replicate

Why has measles reamerged in some countries?

Declining vaccine rates and vaccine misinformation

What hosts can carry measles virus?

Humans only

Progression:

1. respiratory entry

2. replication in respiratory epithelium

3. spread to lymph nodes (primary viremia)

4. Systemic dissemination via blood (secondary viremia

5. infection of conjuctiva, urinary tract, small blood vessels, lymphatics, CNS, and skin

6. prodrome (fever, cough, conjuctiva, Coryza)

7. Koplik’s spots appear on oral mucosa

8. Maculopapular rash begins on head and spreads downward over body, often refusing

9. immune response clears virus, cussing many symptoms

10. recovery in 2-3 weeks

11. complications many occur