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Microbiology > Chapter 38 Exam 3 > Flashcards

Chapter 38 Exam 3 Flashcards

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1
Q

Describe chickenpox (Varicella).

A

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.

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2
Q

Describe the causative agent of chickenpox.

A

the enveloped double stranded DNA varicella-zoster virus, a member of the family Herpesviridae.

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3
Q

Describe the symptoms of chickenpox.

A

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.

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4
Q

Describe the prevention and treatment of chickenpox.

A

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.

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5
Q

What is the reactivated form of chickenpox called?

A

shingles (Herpes zoster).

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6
Q

how does shingles occur?

A

the virus travels down the neuron, initiates viral replication and produces painful vesicles because of sensory nerve damage.

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7
Q

Describe influenza.

A

a respiratory system disease caused by negative strand RNA viruses that belong to the family Orthomyxoviridae.

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8
Q

What are the three genera of influenza?

A

A, B and C

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9
Q

How are influenza viruses acquired?

A

inhalation or ingestion of virus contaminated respiratory secretions.

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10
Q

What happens during the incubation period of influenza?

A

incubation lasts one to two days, viral particles adhere to cells of the host respiratory epithelium by their hemagglutinin spike proteins.

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11
Q

What is the function of hemagglutinin and neuraminidase?

A

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.

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12
Q

What does influenze virus attachment trigger?

A

receptor mediated endocytosis, and encloses the virion in an endosome.

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13
Q

How does the nucleocapsid of the influenza virus enter the cytoplasm?

A

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.

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14
Q

How are influenza viruses classified?

A

based on their membrane surface glycoproteins, hemagglutinin and neuraminidase.

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15
Q

How many antigenic forms of hemagglutinin (HA) and Nueuraminidase (NA) are known?

A

16 HA and 9 NA

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16
Q

Describe plasticity in influenza.

A

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.

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17
Q

Describe influenza antigenic drift.

A

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.

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18
Q

Describe influenza antigenic shift.

A

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.

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19
Q

What are the clinical manifestations of influenza?

A

chills, fever, headache, malaise, and general muscular aches and pains
recovery usually within 3 to 7 days
often leads to secondary infections by bacteria

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20
Q

Describe treatment, prevention and control of influenza.

A

rapid immunologic tests
symptomatic/supportive therapy
inactivated virus vaccine

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21
Q

Describe the measles virus.

A

negative-strand, enveloped RNA virus.

a measles infection provides a lifelong immunity against reinfection.

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22
Q

How does the measles virus enter the body?

A

through the respiratory tract or the conjunctiva of the eyes.

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23
Q

What are the clinical manifestations of measles?

A

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.

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24
Q

What are kopliks spots?

A

lesions of the oral cavity with a bluish-white speck in the center of each. Caused by measles.

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25
What is subacute clerosing panencephalitis?
progressive degeneration of the central nervous system caused by measles.
26
Describe the mumps virus.
pleomorphic, enveloped RNA viruses containing a helical neucleocapsid.
27
How is the mumps virus transmited?
in saliva and respiratory droplets.
28
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.
29
What are respiratory syndromes and viral pneumonia caused by?
acute respiratory viruses, which collectively produce a variety of clinical minfestations.
30
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.
31
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.
32
How is HRSV contracted?
direct contact with respiratory secretions of humans.
33
What are the clinical manifestations of HRSV?
acute onset of fever, cough, rhinitis, and nasal congestions.
34
How is HRSV treated?
inhaled ribavirin. | antibody injections has been shown to reduce severity of disease.
35
Describe the rubella virus.
enveloped, positive-strand RNA virus.
36
How is rubella spread?
droplets that are shed from the respiratory secretions of infected individuals.
37
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.
38
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.
39
What is severe acute respiratory syndrome?
a highly contagious viral disease caused by a novel coronavirus known as the SARS coronavirus.
40
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.
41
What does SARS virus cause?
a febrile lower respiratory tract illness. | headache; mild, flulike discomfort; and body aches.
42
How is SARS transmitted?
by close contact with respiratory secretions.
43
Describe smallpox.
highly contagious illness caused by orthopoxviruses belonging to the species Variola.
44
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.
45
What are the clinical manifestations of smallpox?
systemic aches, acute onset of fever, followed by a rash that features firm, deep-seated vesicles or pustules in the same stage of development without other apparent cause.
46
Describe Variola major
more sever and the most common form of smallpox, with a more extensive rash and higher fever. overall mortality rate of 33% with significant morbidity in those that did not die.
47
Describe Variola minor.
less common, with much less sever disease and death rates of 1% or less.
48
How is variola virus transmitted?
direct and fairly prolonged face-to face contact. direct contact with infected bodily fluids or contaminated objects such as bedding or clothing.
49
How are arthropod-borne viruses transmitted?
by bloodsucking arthropods from one vertebrate host to another.
50
How does the arthropod-borne virus affect the vector?
infects, without causing any disease, the vector develops a lifelong infection. multiplies in the tissues.
51
What are the three subsets of syndromes produced by arthropod-borne viruses?
1. fevers of an undifferentiated type with or without rash. 2. encephalitis often with a high fatality rate. 3. hemorrhagic fever, often sever and fatal.
52
Describe equine encephalitis viruses.
positive strand, enveloped RNA viruses.
53
How is equine encephalitis transmitted?
transmitted to humans by Aedes and Culex species mosquitoes.
54
Describe the West Nile virus.
caused by a positive-strand RNA flavivirus.
55
How is west nile virus transmitted?
predominantly from mosquitoes that feed on infected birds.
56
Describe the HIV virus.
postivie strand, enveloped RNA virus.
57
How is HIV acquired and transmitted?
when infected blood, semen, or vaginal secretions come in contact with an uninfected person's broken skin or mucous membranes.
58
Describe the herpes virus.
double stranded DNA virus. | icosahedral capsids, and are enveloped.
59
What are the clinical manifestations of herpes virus?
blisters are the result of cell lysis and the development of a local inflammatory response; they contain fluid and infectious virions. Fever, headache, muscle aches and pains, a burning sensation, and general soreness occur.
60
Why is the incidence of the common cold greater in the winter months?
increased population density indoors, the effect of dry winter air on mucous membranes, and decreased immune function that results from cold temperatures.
61
Describe the rhinovirus.
nonenveloped, positive strand RNA viruses. | 115 different serotypes.
62
How does the rhinovirus cause infection?
viral invasion of the upper respiratory tract is the basic mechanism in the pathogenesis. The virus enters the body's cells by binding to cellular adhesion molecules
63
What are the clinical manifestations of the rhinovirus?
nasal stuffiness, sneezing, scratchy throat, water discharge from the nose.
64
Describe the human cytomegalovirus.
enveloped, double-stranded DNA virus with an icosahedral capsid.
65
What kinds of people does human cytomegalovirus typically affect?
those who have had an organ transplant and immunocompromised people.
66
What does the human cytomegalovirus cause?
the cells to swell in size. interferance with many host immune functions, such as antigen presentation, cytokine production, and natural killer cell activity.
67
Describe how the prevalence of cytomegalovirus can change.
increases with a decrease in socioeconomic status.
68
What is genital herpes caused by?
herpes simplex virus, specifically type 2.
69
How does infection of genital herpes occur?
the virus is introduced into a break in the skin or mucous membranes. infects the epithelial cells of the external genitalia, the urethra, and the cervix.
70
Describe the human herpesvirus 6
virus envelope encloses an icosahedral capsid and a core containing double stranded DNA.
71
What are the clinical manifestations of human herpesvirus 6?
high fever of 3 to 4 days' duration, after which the temperature suddenly drops to normal and a macular rash appears on the tunk and then spreads to other areas of the body.
72
What kind of cells are involved in the replication of human herpesvirus 6?
CD4+ cells are the main site
73
Describe human parvovirus B19.
uniform, icosahedral, naked particles approximately 23 nm in diameter. single stranded DNA molecules.
74
When is the only time that human parvovirus DNA can be replicated?
during the S phase of the S cycle.
75
What are the clinical manifestations of human parvovirus B19?
fever, headache, chills, malaise, erythema infectiosum in children, and a joint disease syndrome in adults.
76
Describe the Epstein-Barr virus.
icosahedral capsid surrounded by an envelope. contains viral double stranded DNA in linear form in the mature virion and circular form in latently infected hosts.
77
What disease does the Epstein-Barr virus cause?
infectious mononucleosis.
78
How can EBV be spread?
by mouth to mouth contact or shared drinking bottles and glasses.
79
What are the clinical manifestations of infectious mononucleosis?
enlargement of lymph nodes and spleen, sore throat, headache, nausea, general weakness and tiredness, and a mild fever that usually peaks in the early evening.
80
What is hepatitis?
inflammation of the liver.
81
Describe the hepatitis B virus.
enveloped virus having a partially double stranded circular DNA genome of complex structure. reverse-transcribing DNA viruses, so named because they encode a reverse transcriptase enzyme that is used to generate their genomes.
82
Where does replication of hepatitis B take place?
in hepatocytes.
83
How is Hepatitis B transmitted?
through blood or other body fluids and body-fluid contaminated equipment. can also pasds through the placenta.
84
What are the clinical manifestations of Hepatitis B?
most cases are asymptomatic sometimes fever, loss of appetitie, abdominal discomfort, nausea, fatigue and other symptoms gradually appear. jaundice.
85
describe the hepatitis C virus.
enveloped virion that contains a single strand of linear RNA.
86
How is hepatitis C transmitted?
by contact with virus-contaminated blood, fecal-oral route, in utero transmittion from mother to fetus, sexually, or through organ transplantation.
87
Describe the hepatitis D virus.
a satellite that is dependent on hepatitis B to provide the envelop protein for its RNA genome.
88
How is hepatitis D virus spread?
spread only to persons who are already infected with hepatitis B or to individuals that get the hepatitis B virus and the satellite at once.
89
What are warts caused by?
the human papilomavirus.
90
What is acute viral gastroenteritis?
inflammation of teh stomach or intestines.
91
What are the four major categories of viruses that cause acute viral gastroenteritis?
rotaviruses, adenoviruses, caliciviruses, and astroviruses.
92
What are the clinical manifestations of acute viral gastroenteritis?
asymptomatic relatively mild diarrhea with a headach and fever sever, water nonblood diarrhea with abdominal cramps.
93
How is hepatitis A usually transmitted?
by fecal contamination of food or drink, or shellfish that live in contaminated water.
94
Describe the hepatitis A virus.
icosahedral, linear, positive-strand RNA virus that lacks an envelope.
95
What happens once the hepatitis A virus enters the digestive system?
the viruses multiply within the intestinal epithelium. usually only mild intestinal symptoms result.
96
Describe the hepatitis E virus.
single, positive-strand RNA virus. | spherical, non-enveloped.
97
Describe how hepatitis E is transmitted.
infection usually is associated with feces-contaminated drinking water. HEV enters the blood from the gastrointestinal tract, replicates in the liver, is released from hepatocytes into the bile, and is excreted in the feces.
98
Describe the poliovirus.
nonenveloped, positive stranded RNA virus.
99
How is the poliovirus transmitted?
fecal-oral route.
100
What happens once the poliovirus is ingested?
the virus multiplies in the mucosa of the throat or small intestine. the virus invades the tonsils and lymph nodes of the neck and terminal portion of the small intestine.
101
Describe viral hemorrhagic fever.
sever, multisystem syndrome caused by several distinct viruses. vascular system is damaged, resulting in vascular leakage and dysfunction.
102
What is Ebola hemorrhagic fever?
hemorrhagic fever caused by the ebola virus, first recognized near the ebola river in the democratic republic of the congo in africa.
103
describe the hantavirus.
negative-strand RNA virus.
104
How is hantavirus transmitted?
inhalation of viral paricles shed in urine, feces, or saliva of infected rodents.
105
Describe the rabies virus.
bullet-shaped virion containing a negative-strand RNA genome.
106
Where does the rabies virus multiply?
in the salivary glands.l
107
How is the rabies virus transmitted?
by the bite of an infected animal whose saliva containes the virus.
108
What are the symptoms of rabies?
anxiety, irritability, depression, fatigue, loss of appetite, fever, sensitivity to light and sound.
109
What are prion diseases also called?
transmissible spongiform encephalopathies.
110
What are TSEs?
fatal neurodegenerative disorders that have attracted enormous attention not only for their unique biological features but also for their impact on public health.
111
What are prions thought to consist of?
abnormaly folded proteins, which can induce normal forms of the protein to fold abnormally.
112
What diseases are included in the prion disease classification?
scrapie, kuru, creutzfeldt-jakob disease....

Microbiology (6 decks)

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