Measles, Mumps, Rubella Flashcards
What is the structure of the paramyxoviruses (measles, mumps)?
Single stranded RNA in a helical nucleocapsid
Surrounded by lipid bilayer (wimpy) envelope
Envelope studded with virus encoded glycoproteins
How is measles spread?
Respiratory droplets
What is the pathogenesis of measles?
Infects respiratory epithelial cells of susceptible hosts
Incubates (virus replicates) and spreads to lymph nodes
Primary viremia infects respiratory epithelium and T cells
How long is the incubation period of measles?
10 days (until fever, rash appears day 14)
What are the first clinical manifestations of a measles infection?
3 C’s: Cough, coryza (runny nose), and conjunctivitis
Fever
What clinical manifestations of measles infection appear later on?
Koplik spots on buccal mucosa
Rash appears 4 days after fever
What are the characteristics of a measles rash?
Erythematous, maculopapular, coalesces to become confluent
Begins at hairline and spreads downwards
What makes measles such a deadly illness?
Causes transient but profound immunosuppression, making hosts susceptible to secondary infections
Also causes encephalitis
(sub acute scleroising panencephalitis can appear years later)
What is the most common cause of death in someone with a measles infection?
Pneumonia
What increases the severity of the measles infection?
Malnutrition Immunodeficiencies (HIV) Vitamin A deficiency
How is measles diagnosed?
Clinical
Serology (IgM, paired acute-convalescent IgG)
Viral culture (difficult, can tell you if strains are related)
PCR
When is the measles vaccine given?
Given combined with mumps and rubella as MMR+/-V
Two doses given after 1 yo
(in endemic countries, vaccine given once at 9 mo)
What is the pathogenesis of mumps?
Infection in upper respiratory tract epithelium
Spreads to local lymph nodes
Viremia infects various sites (salivary glands, cochlea, seminiferous tubules)
CMI controls infection but also causes most of symptoms
How is mumps transmitted?
Respiratory droplets
When is someone with measles most infectious?
Before the rash appears (1-14 days after exposure)
When is someone with mumps most infectious?
2 days before salivary swelling to 5 days afterwards
What are clinical features of mumps?
1/3 asymptomatic
Characterized by swelling of salivary glands, particularly parotid
Can get swelling of other glandular tissue (testes)
What are complications of mumps infection?
Encephalitis
Deafness
Infertility
How is mumps diagnosed?
Clinical
Serology: IgM, IgG
Culture (saliva, CSF)
PCR (Can be positive after vaccine)
What family and genus is Rubella in?
Togavirus family, Rubivirus genus (only member)
What is the structure of Rubella?
Single stranded RNA
Lipid envelope (wimpy)
Glycoprotein spikes on surface
How is Rubella spread?
Respiratory droplets
Vertical transmission
What is the pathogenesis of Rubella?
NOT cytolytic
Infects upper respiratory tract
Spreads to local lymph nodes
Antibody develops and CMI eliminates infection
How long is the incubation period of mumps?
2-3 weeks
How long is the incubation period of rubella?
2-3 weeks
When is someone with rubella most infectious?
Prodrome period (before symptoms) until 2 weeks after rash
What are clinical symptoms of post-natally acquired Rubella?
Rash
Cervical lymphadenopathy
Arthritis
The symptoms of Rubella are mild, so why do we vaccinate?
Congenital rubella has more serious effects
What are clinical symptoms of congenital Rubella syndrome?
Triad of: Cataracts, Heart disease, Deafness
Also: hepatosplenomegaly, “blueberry muffin rash”, mental retardation
How is Rubella diagnosed?
Clinical
Serology (IgM, IgG)
PCR
Culture (difficult)
What is the structure of Parvovirus B19?
Very small
Non-enveloped (sturdy), icosahedral capsid
One linear, single stranded DNA
What is the pathogenesis of Parvovirus?
Replicates in respiratory tract
Spreads by viremia to bone marrow where it replicates in and kills RBC precursors (anemia-causing)
Immune response dictates second phase (rash, arthritis)
How is Parvovirus transmitted?
Respiratory droplets, blood products, vertical transmission
When is someone with Parvovirus most infectious?
Until rash appears
How long is the incubation period of Parvovirus?
4-14 days (rash appears 7-10 days later)
What is the appearance of the Parvovirus rash?
Slapped cheek
How does Rubella rash differ from Measles rash?
Rubella goes head to toe like measles, but fades as it progresses (unlike measles)
What are clinical symptoms of Parvovirus?
Asymptomatic in 75%
Others show fever, distinctive rash days after fever, arthritis
What are complicatoins of Parvovirus infection?
Anemia (transient aplastic crisis in those with hemoglobinopathy like sickle cell)
Fetal hydrops if mother infected in first half of pregnancy
Myocarditis
How is Parvovirus diagnosed?
Clinical
Serology: IgM, IgG
PCR (blood or amniotic fluid)
Which infections from this lecture do you not want if pregnant?
Parvovirus
Rubella
Which infections from this lecture do you not want if you have sickle cell?
Parvovirus
Which of these infections have secondary bacterial infectious as the leading cause of death?
Measles
Which of these infections have rash at the same time as fever?
Rubella
Which of these infections have rash after fever?
Parvovirus
Measles
Which of these infections was once a leading cause of deafness?
Mumps
