MMR Flashcards
what is the organism that causes measles?
Morbillivirus genus
what is the genome of measles?
Single stranded
non-segmented
RNA
what are the features of measles?
Cell membrane derived envelope Replicates in cytoplasm Major killer in developing world (1 million children / year ) Transmission by aerosol droplets Very contagious No therapy - supportive care only
what is the structure of the measles virus?
Haemagglutinin-neurominidase (like flu)
genome in 1 big long strand
fusion protein in the lipid bilayer
how is measles transmitted?
All discharges carry virus
Contact with infected person
Viral particles remain infectious for several hours
Aerosol transmission ONLY over short distances
what is the pathogenesis of measles?
Damage due to viral invasion, cytopathic changes and host response
Virus replicates in respiratory tract and mucosae
Infects lymphoid tissue and bone marrow
Infects epithelial cells
what are the symptoms of measles?
9-11 days after exposure to virus - fever of 38.3°C
Coryza (runny nose) and cough (virus attacks respiratory tract)
Conjunctivitis (sore eyes)
Koplik’s spots (virus attacks mucosa) 1-3 days after respiratory symptoms
Maculopapular rash (virus attacks epithelial cells) develops a day after Koplik’s spots
Lymphadenopathy – immune suppression
what are the characteristics of a measles rash?
Virus antigens and particles in the tissues
Develops over 2-3 days and then fades
T-cells targeting infected endothelial cells in the small blood vessels
how are Koplik’s spots described?
“grains of salt surrounded by red halo”
salt crystals
what is the sequence of antibodies produced against measles?
IgM - first antibodies
IgG - specific - produced later
Typical case study:
Developed rash in last 24 hours
Unwell for 3 days, fever, runny nose and unproductive cough
On examination as well as a rash, patient miserable and febrile, no evidence of lower respiratory tract disease
What is it?
Measles
how can you diagnose measles?
Koplik’s spots - small greyish white lesions in mouth that fade once rash appears
Virus isolation (from onset of symptoms - day 2-3 of rash) expensive & slow technique
Serodiagnosis: haemagglutination inhibition or ELISA
typical case study COMPLICATIONS:
Rash spreads to trunk and limbs and begins to fade, leaving a brownish discolouration.
Respiratory symptoms improve and fever subsides.
Day 6 after onset of rash, patient complains of headache, becomes increasingly irritable and fever returns.
what is it?
measles
what are the complications of measles?
Superinfection of middle ear or lung - viral or bacterial pneumonia
Secondary infection with varicella-zoster virus & influenza virus
Neurological complication - Meningoencephalitis (1/1000 cases) deafness, mental retardation, seizures
Neurological complication - Subacute sclerosing pan encephalitis (SSPE). Develops 1- 10 years after disease, progressive resulting in coma and death. Incidence decreased since vaccination.
what are the characteristics of measles in developing countries?
Immunosuppressive effects linked to malnutrition
Infection complicated by bacterial pneumonia & diarrhoea
Major cause of death (5 -15% mortality)
how has the number of measles cases dropped due to vaccinations?
In 2015, there were 134 200 measles deaths globally – about 367 deaths every day or 15 deaths every hour.
Measles vaccination resulted in a 79% drop in measles deaths between 2000 and 2015 worldwide.
In 2015, about 85% of the world’s children received one dose of measles vaccine by their first birthday through routine health services – up from 73% in 2000.
During 2000-2015, measles vaccination prevented an estimated 20.3 million deaths making measles vaccine one of the best buys in public health
what are the characteristics of MMR vaccination?
Live attenuated vaccine - stable under refrigeration
Inexpensive
Administered as MMR - with mumps and rubella vaccines
Gives long term immunity
Does not spread from vaccinated person
what organism causes mumps?
Rubulavirus Genus
what virus is mumps similar to?
Paramyxovirus
how many serotypes of mumps are there?
1
what is the reservoir of mumps
humans ONLY
what is the pathogenesis of mumps?
Respiratory infection - virus replicates in nasopharynx
Spreads to regional lymph nodes
Viremia (virus in blood) - spread to multiple tissues causing inflammation
Salivary glands to cause inflammation (parotitis)
Meninges (lining of brain) to cause aseptic meningitis
Testes to cause inflammation (orchitis)
what are the symptoms of mumps?
Fever and headache
Muscle aches
Tiredness and loss of appetite
Parotitis (inflammation of salivary glands)
observed in around 40% patients
persists 7-10 days
Meningitis occurs - usually mild
50% patients asymptomatic
but more severe in adults
typical case study:
Developed pain tenderness and difficulty swallowing in last 24-48 hours
Unwell for 3 days, fever, sickness and headache
On examination patient is miserable and febrile with swelling of one or more parotid glands
what is it?
mumps
