Mumps and Measles Flashcards
Mumps and measles
Type of Virus
Paramyxoviruses
Paramyxoviruses
Brief review of structure of paramyxoviruses:
• Enveloped virion
• Nucleocapsid has helical symmetry
• Genome consists of single molecule of RNA
• RNA genome is minus-stranded
• Virion carries a RNA polymerase
• Virion hemagglutinate red cells
Genetic Structure of Mumps & Measles
Paramyxoviruses
- The minus-stranded viral RNA is in one piece
- Genetic reassortment is impossible.
- This is in contrast to Influenza (orthmyxovirus) that undergoes genetic reassortment
Mode of Infections
Influenza & Parainfluenza
Influenza (orthomyxovirus) and parainfluenza (paramyxovirus) viruses generally cause local, nonsystemic, nonviremic infections.
Mode of Infections
Mumps & Measles
Mumps and measles are paramyxoviruses that cause systemic infections with viremia as an essential step in pathogenesis
Consequence of Viremia in Mumps and Measles
a. Incubation period is longer for mumps and measles because cycles of multiplication in several sites in succession are required.
b. Lifelong immunity occurs in individuals who have had the disease. Obligatory viremia allows neutralization by IgG.
Mumps
Mumps is caused by a paramyxovirus that is antigenically related to the parainfluenza viruses.
There is one serotype of mumps virus and humans
are the sole reservoir of mumps.
Mumps Pathogenesis
Mumps is transmitted via respiratory droplets. After
an average incubation period of typically around 18-21 days a prodromal period of fever, malaise & anorexia is quickly followed by unilateral or bilateral swelling of the parotid gland. The usual presenting clinical symptom is PAROTIDITIS.
Parotiditis
Mumps
Mumps virus grows in the enlarged painful
parotid salivary glands and is excreted in saliva
several days before and after swelling of the salivary
gland begins. Parotiditis begins about 18-21 days after infection (3 week incubation period).
Pain arises only from pressure within organs in tight capsules, e.g. parotid gland and testis (orchitis) after puberty. Most infections are symptomatic (only 30% are asymptomatic)
Transmission of Mumps
Transmission occurs by respiratory exposure with saliva droplets containing mumps virus.
Primary virus multiplication is in respiratory epithelium and local lymph nodes. This results in viremia that infects salivary glands and other organs.
The virions produced int he salivary glands go down the duct to the mouth and provide most of the infectious virions spread by coughs and sneezes.
Orchitis
Mumps
It’s seen inabout 30% of infected males past puberty. Orchitis is quite painful inflammation of the testicles.
Unilateral orchitis resolves with no other complications.
Bilateral orchitis can result in sterility or subferterlity, although this outcome is uncommon.
Other organs infected
Mumps
Other organs affected include the pancreas, the ovary (both uncommon) and, much more commonly, the meninges (aseptic meningitis). All have a generally benign course.
Immunity
Mumps
Immunity is generally lifelong even after subclinical infection.
Treatment
Mumps
There is no antiviral therapy for mumps.
Immunization
Mumps
Immunization uses a live attenuated vaccine. The mumps vaccine is a component of the MMR pediatric vaccine that is given twice to confer protection without serious side effects.
The incidence of infection has fallen markedly in developed countries because of childhood immunization.
Measles
Measles is caused by a paramyxovirus. It is antigenically unrelated to any other paramyxovirus of humans.
Measles (General Info)
Measles is probably the most contagious disease known.
Also, in contrast to most other viruses, it almost never causes subclinical infections. Before the vaccine era there were local epidemic generally every three years, in winter.
Measles Epidemics
a. The measles virus causing the epidemic is antigenically the same measles virus (epidemics occur with no antigenic variation).
b. The number of nonimmune susceptibles increases because of new births.
c. When the concentration of nonimmune susceptibles is sufficient to break down herd immunity, measles virus can be introduced
and is rapidly disseminated in the population causing a new epidemic.
Transmission of Measles
a. Measles virus is efficiently transmitted via respiratory droplets. Measles virus infects via respiratory tract and initially multiplies in epithelium and local lymph nodes (also conjunctiva).
b. Asymptomatic infections are rare/unknown.
Symptoms of Measles
Before the rash, various PRODROMAL SYMPTOMS (prodromal symptoms are those nonspecific symptoms that appear before the definitive symptoms) appear: fever, cold-like symptoms, runny nose, red eyes.
Just prior to the definitive symptoms of the measlesrash, Koplik spots (bright red lesions with a
white central spot on the buccal mucosa) are seen
and is predictive of the measles rash appearing in a
day or two (Koplik’s spots = measles). Along with the appearance of the measles rash, fever, runny nose, coughing/sneezing, conjunctivitis, and photophobia are common symptoms.
Measles Rash
The rash begins after a 14-day incubation period.
The measles rash is described as a generalized
maculopapular erythematous rash. The immune response plays a role in the genesis of the rash.
Measles Virus Shedding
Virus excretion from respiratory tract and in tears and urine for a few days before and after appearance of the rash.
Measles Prognosis
- 0.1 - 0.3 death rate from Measles in the USA
- 5-25% death rate in developing countries
- In developed countries, 1 in 20 cases result in pneumonia
- Otitis media is frequent
- Acute encephalitis (1-2 in 1000 cases) leading to 500 deaths and 1500 retarded survivors per in USA in 195–1960 before immunization
Treatment for Measles
- There are no treatments for measles
* Immune response ultimately eliminates viral excretion and confers life long immunity
