deck_524014 Flashcards
review of structure of paramyxoviruses- enveloped?- nucleocapsid symmetry?- genome structure?- -/+ stranded?
enveloped virionhelical symmetrygenome consists of a single molecule of RNARNA genome is minus-stranded
what type of virus are mumps and measles?
paramyxoviruses
are mumps and measles antigenically related to parainfluenza viruses?
mumps ismeasles is not
describe mumps and measles:- nucleocapsid- genome- +/– envelope?
helical nucleocapsidminus-stranded RNAenvelope with virus-specified glycoproteins
do mumps and measles hemagglutinate red cells?
yes
do paramyxoviruses carry an RNA polymerase?
yes
can measles and mumps viruses reassort? why or why not?
since the RNA is only one piece, genetic reassortment is impossibleas a result, no significant antigenic variation has been seen
what types of infections do mumps and measles (and paramyxoviruses) cause?
systemic infections with viremia as an essential step in pathogenesis
what is an essential step in the pathogenesis of mumps and measles
viremia
what kinds of infections do orthomyxoviruses and paramyxoviruses generally cause?
local, nonsystemic noviremic infections
what is the significance of the fact that mumps and measles cause systemic infection (summary)?
incubation period is longer for mumps and measles because cycles of multiplication in several sites in sucession are requiredlifelong immunity occurs in individuals who have had the disease - obligatory viremia allows neutralization by IgG
how does the incubation period of mumps and measles compare with that of orthomyxoviruses and paramyxoviruses (so flu and paraflu)?
it’s longer because the cycles of multiplication is several sites in succession are required to establish infection in mumps and measles
how long is immunity to mumps and measles after infection?
lifelong
what antibody type is involved in the reaction to mumps and measles?
obligatory viremia allows for neutralization by IgG
how many serotypes of mumps are there?
only one
how many types of species can mumps infect?
humans are the sole reservoir of mumps
how is mumps transmitted?
by respiratory droplets
how long is the average incubation period of mumps before symptoms appear?
18 days
what are the symptoms of mumps? what would allow you to diagnose mumps (ie what would you look for)?
around 18 days, a prodromal period of fever, malaise, and anorexia is followed by unilateral or bilateral swelling of the parotid gland (parotiditis) = usual presenting clinical symptomwill have inflamed parotid duct (stensens duct) in mouthalso get orchitis in males after age of puberty
what is paratiditis
caused by mumpsinfection of the parotid glandthe virus grows in the enlarged parotid salivary glands becomes painfulis excreted in saliva several days before and after swelling of the gland begins
why does mumps cause pain?
pressure and swelling within organs in tight capusles, so ones like the parotid gland and testis (orchitis) after puberty
are most mumps infections symptomatic or asymptomatic?
most are symptomatic - only 30% are subclinical/asymptomatic
where does mumps virus multiply, primarily?
in respiratory epithelium and local lymph nodes
what is the result of primary mumps multiplicaton (ie what’s the secondary step in infection)?
in viremia that spreads to the salivary glands and other organs
where do most of the infectious virions in mumps come from?
they are produced in the salivary glandsthey go down the duct to the mouth and are spread by coughs and sneezes
how long does it take for parotiditis to begin in a mumps infection?
about 18-21 days = a three week incubation period
how frequent is orchitis in mumps infections?
occurs in about 30% of infected males past puberty
what is orchitis?does it resolve?who can get it?
painful inflammation of the testiclescaused by mumpsunilateral orchitis resolves with no other complicatoinsbilateral can result in sterility or subfertility but this outcome is uncommononly in adults after puberty because children don’t have fibrous capsule yet
what organs are affected by mumps?
testicles, parotid glanduncommonly the pancrease and ovarymore commonly the meninges (aseptic meningitis)all have a generally benign course
how long is the immunity to mumps after infection?
generally lifelong, even after subclinical infection
is there an antiviral therapy for mumps?
no
is there a vaccine for mumps? if there is, what kind of vaccine is it and how is it administered (timing)?
yes, there is a live-attenuated vaccineit’s administered as a component of the MMR pediatric vaccine given twice to confer protection without serious side effectsincidence of infection has fallen in developed countries because of childhood immunization
what has been the incidence of infection in developed countries recently?
the incidence has fallen markedly because of childhood immunization but there have been some recent epidemics
what kind of virus is measles? is it antigenically related to other viruses of its type?
measles is a paramyxovirusit is unrelated to any other paramyxoviruses in humans
how often does measles cause subclinical infections?
almost never
pre-vaccination, how often were there measles epidemics?
local epidemics occured generally every three years in the winter
what were the causes of measles epidemics?
1: the number of nonimmune susceptibles increases because of births2: epidemics occur when the number of nonimmune susceptibles becomes sufficient to break down herd immunitynote: there is no antigenic variation between the strain that causes epidemic and other strains, unlike flu
how is measles transmitted?
respiratory droplets
how/where does measles infect?
via the respiratory tractinitially multiplies in the epithelium and local lymph nodes and conjunctiva
what are the prodromal symptoms of measles?
fever, cold-like symptoms, runny nose, red eyesphotophobia is also a common symptom
what is the definitive symptom of measles?
rashKoplik spots - bright red lesions with a white central spot on the buccal mucosa - appear first and then rash appears in a day or two the rash is described as a generalized maculopapular erythematous rash
at what point after measles infection would you expect to see a rash appear?
after a 14-day incubation period
what, besides the virus, plays a role in the development of the rash seen in measles?
the immun response
how and when is measles virus excreted?
excreted from the respiratory tract and in tears and urinefor a few days before and after appearance of the rash
how common are complications from measles infection in developed countries?
can be mild to severe (death)death rate in us from measles infection is 1 to 3 deaths per 1000 cases
what are common complications of measles in developed countries?
1: 1 in 20 result in pneumonia (sometimes due to a secondary bacterial infection2: otitis media (generally bacterial)3: acute encephalitis in about 1 to 2 per 1000 cases
in what cohort of patients would you expect to see complications from measles?
in adults and in those who are immune compromised
how is measles treated?
there is no specific treatment, but could give antibodies to measles from the sera of immune individuals to help a bit
what is the effect of the immune response to measles (ie is it effective and for how long)?
immune response eliminates viral excretionconfers life-long immunity without requiring restimulation by contact with exogenous virus
what is the pathology of measles virus?
measles causes the formation of multinucleated giant cells in lymphoid tissue and respiratory mucosa (virus-induced cell fusion)
what is the mechanism behind the pathology of the measles virus?
the measles fusion protein is inserted into infected cell plasma membranes, causing it to fuse with surrounding cells
what is the effect of measles on cell-mediated immunity?
measles infection suppresses cell-mediated immunityeg: delayed hypersensitivity skin tests (such as the TB test) become negative for a few weeks or even months in a child who was positive before contracting measles = anergy