Chapter 38 Exam 3 Flashcards
Describe chickenpox (Varicella).
a highly contagious skin disease primarily of children two to seven years of age. Humans are the reservoir and the source, which is acquired by droplet inhalation into the respiratory system.
Describe the causative agent of chickenpox.
the enveloped double stranded DNA varicella-zoster virus, a member of the family Herpesviridae.
Describe the symptoms of chickenpox.
following an incubation period of 10 to 23 days, small vesicles erupt on the face or upper trunk, fill with pus, rupture, and become covered by scabs. Healing occurs in about ten days. During this time, intense itching often occurs.
Describe the prevention and treatment of chickenpox.
the attenuated varicella vaccine in the 1990s has drastically reduced the incidence of chickenpox.
infection can be shortened with the drug acyclovir.
individuals who recover from chickenpox are subsequently immune to the disease, however the viral DNA resides in a dormant state within the nuclei of cranial nerves and sensory neurons in the dorsal root ganglia.
What is the reactivated form of chickenpox called?
shingles (Herpes zoster).
how does shingles occur?
the virus travels down the neuron, initiates viral replication and produces painful vesicles because of sensory nerve damage.
Describe influenza.
a respiratory system disease caused by negative strand RNA viruses that belong to the family Orthomyxoviridae.
What are the three genera of influenza?
A, B and C
How are influenza viruses acquired?
inhalation or ingestion of virus contaminated respiratory secretions.
What happens during the incubation period of influenza?
incubation lasts one to two days, viral particles adhere to cells of the host respiratory epithelium by their hemagglutinin spike proteins.
What is the function of hemagglutinin and neuraminidase?
hemagglutinin is required for binding of individual virions to host cell receptors and the subsequent fusion of the viral envelope with the host endosomal membrane, initiating infection. neuraminidase facilitates release of newly assembled influenza virions from infected cells by cleaving sialic acid residues between virus and host membranes.
What does influenze virus attachment trigger?
receptor mediated endocytosis, and encloses the virion in an endosome.
How does the nucleocapsid of the influenza virus enter the cytoplasm?
the hemagglutinin moleules in the virus’s envelope undergoes a dramatic conformational change when the endosomal pH decreases. The hydrophobic ends of the hemagglutinin spring outward and extend toward the endosomal membrane. After they contact the membrane, fusion occurs and the RNA nucleocapsid is released into the cytoplasm.
How are influenza viruses classified?
based on their membrane surface glycoproteins, hemagglutinin and neuraminidase.
How many antigenic forms of hemagglutinin (HA) and Nueuraminidase (NA) are known?
16 HA and 9 NA
Describe plasticity in influenza.
they change frequently due to point mutations and reassortment of the RNA segments. Leads to the sudden appearance of new influenza viruses that cause pandemics.
Describe influenza antigenic drift.
the protein variation between one strain and the next after plasticity is extremely small.
Results from the accumulation of mutations of HA and NA in a single strain of flu virus within a geographic region.
Describe influenza antigenic shift.
a large antigenic change between one strain and the next resulting from the reassortment of genomes when two different strains of flu viruses infect the same host cell and are incorporated into a single new capsid.
What are the clinical manifestations of influenza?
chills, fever, headache, malaise, and general muscular aches and pains
recovery usually within 3 to 7 days
often leads to secondary infections by bacteria
Describe treatment, prevention and control of influenza.
rapid immunologic tests
symptomatic/supportive therapy
inactivated virus vaccine
Describe the measles virus.
negative-strand, enveloped RNA virus.
a measles infection provides a lifelong immunity against reinfection.
How does the measles virus enter the body?
through the respiratory tract or the conjunctiva of the eyes.
What are the clinical manifestations of measles?
nasal discharge, cough, fever, headache, and conjunctivitis, which intensify several days prior to the onset of rash.
skin eruptions occur as erythematous maculopapular lesions that are at first discrete but gradually become confluent.
What are kopliks spots?
lesions of the oral cavity with a bluish-white speck in the center of each. Caused by measles.
What is subacute clerosing panencephalitis?
progressive degeneration of the central nervous system caused by measles.
Describe the mumps virus.
pleomorphic, enveloped RNA viruses containing a helical neucleocapsid.
How is the mumps virus transmited?
in saliva and respiratory droplets.
What are the clinical manifestations of mumps?
swelling and tenderness of the salivary glands.
rare complications include meningitis, encephalitis, and inflammation of the epididymis and testes leading to sterility.
What are respiratory syndromes and viral pneumonia caused by?
acute respiratory viruses, which collectively produce a variety of clinical minfestations.
Describe the human respiratory syncytial virus (HRSV).
negative-strand RNA virus, variable in shape and size and enveloped with two virus-specific glycoproteins as part of the structure.
What does HRSV cause?
fusion of plasma membranes of infected cells (syncytium). syncytia are responsible for inflammation, alveolar thickening, and the filling of alveolar spaces with fluid.
How is HRSV contracted?
direct contact with respiratory secretions of humans.
What are the clinical manifestations of HRSV?
acute onset of fever, cough, rhinitis, and nasal congestions.
How is HRSV treated?
inhaled ribavirin.
antibody injections has been shown to reduce severity of disease.
Describe the rubella virus.
enveloped, positive-strand RNA virus.
How is rubella spread?
droplets that are shed from the respiratory secretions of infected individuals.
What are the symptoms of rubella?
incubation ranges from 12 to 23 days.
rash of small red spots, usually lasting 3 days, and a light fever.
Describe congenital rubella syndrome.
rubella can be a disastrous disease in the first trimester of pregnancy and can lead to fetal death, premature delivery, or a wide array of congenital defects.
Also causes brain damage that leads to cognitive disabilities.
What is severe acute respiratory syndrome?
a highly contagious viral disease caused by a novel coronavirus known as the SARS coronavirus.
Describe coronaviruses.
positive-strand RNA viruses.
relatively large, composed of RNA within a helical nucleocapsid, surrounded by an envelope.
large spikes aid in attachment and entry into host cells.
What does SARS virus cause?
a febrile lower respiratory tract illness.
headache; mild, flulike discomfort; and body aches.
How is SARS transmitted?
by close contact with respiratory secretions.
Describe smallpox.
highly contagious illness caused by orthopoxviruses belonging to the species Variola.
Describe the variola virus virion.
large, brick-shapes, and contains a dumbbell-shaped core. The genome inside the core consists of a single, linear molecules of double-stranded DNA that is replicated in the host’s cell membrane.
