MycoViro 64 Part 1 Flashcards
Viruses that established a long-term relationship with their host (i.e., did not kill the host immediately upon infection) were the first to become adapted to coevolution with the human race. Some of these earliest viruses were believed to be retroviruses such as (2)
herpes viruses and papillomaviruses
is a submicroscopic, obligate intracellular para- site, among the smallest of all infectious agents, and capable of infecting any animal, plant, or bacterial cell.
virus
Virus are strict obligate intracel- lular parasites, incapable of replication without a?
living host cell
Virus types are very specific, and each has a limited number of hosts it can infect; this is referred to as?
viral tropism
Trans- mission of viruses from animals to humans still occurs, as demonstrated in the more recent viral outbreaks associated with the?
severe acute respiratory syndrome (SARS)
West Nile
influenza A H5 viruses
2009 H1N1 virus, formerly known as the pandemic “swine flu.”
SARS-CoV-2 virus A.K.A COVID-19
_______ has proven to be one of the deadliest viruses to affect humans; its history dates back to the 1700s in Italy.
influenza virus
influenza virus: The virus was named to indicate disease resulting from the “influence” of?
miasma (bad air)
The emergence of a new viral disease across a very large geographic region (worldwide) with prolonged human-to- human transmission is called a?
pandemic
Pandemics result when an influenza virus undergoes a _________ and the reassortment of genes combines with those of another organism, usually an ani- mal.
genetic shift
The resulting virus emerges as a completely?
new or “novel” virus
The genetic changes in viral genomes may result from ________ (major changes that result in novel viral antigens) and/or ________ (minor changes that occur infrequently), which are discussed in Chapter 65.
antigenic shift; antigenic drift
major changes that result in novel viral antigens
antigenic shift
minor changes that occur infrequently
antigenic drift
One of the most deadly influenza outbreaks was the _______ pandemic of 1918 to 1919.
Spanish flu
Spanish flu: This pandemic was associated with infection with a novel influenza virus of?
avian origin
_________ has proven to be a valuable tool in the control of viral diseases such as yellow fever and rabies and has been instrumental in the eradication of one of the most lethal viruses, small- pox.
Vaccination (immunization)
Vaccination (immunization) has proven to be a valuable tool in the control of viral diseases such as yellow fever and rabies and has been instrumental in the eradication of one of the most lethal viruses, small- pox. However, many viral diseases such as (3) continue to pose challenges in treatment, prevention, and control.
influenza, acquired immunodeficiency syndrome (AIDS), and hepatitis
Virus particles, referred to as?
virions
Virus particles, referred to as virions, consist of two or three parts:
• An inner nucleic acid core, consisting of either ribonu-
cleic acid (RNA) or deoxyribonucleic acid (DNA)
• A protein coat that surrounds and protects the nucleic
acid (the capsid)
• In some of the larger viruses, a lipid-containing envelope
that surrounds the virus
An inner nucleic acid core, consisting of either
ribonu-
cleic acid (RNA) or deoxyribonucleic acid (DNA)
protein coat A.K.A
Capsid
Because enveloped viruses are very susceptible to drying and destruction in the environment, they typically are trans- mitted by direct contact, such as? (3)
respiratory, sexual, or par- enteral contact
Viruses that do not have an envelope are often referred to as?
“naked” viruses
Naked viruses are very resis- tant to environmental factors. Because of their stability, they typically are transmitted by the?
fecal-oral route
Many viruses have _______ spikes extending from their sur- face.
glycoprotein
The term ________ is often used to describe the nucleic acid genome surrounded by a symmetric protein coat
nucleocapsid
The function of the nucleic acid genome is to encode the proteins required for? (3)
viral penetration, transmission, and replication
A variety of viral genome structures exist, including? (3)
(+) sense–strand RNA, (–) sense– strand RNA, and DNA genomes
A variety of viral genome structures exist, including (+) sense–strand RNA, (–) sense– strand RNA, and DNA genomes. In addition, viral genomes may be?
single- or double-stranded molecules
The ________ protects the viral genome and is re- sponsible for the tropism to specific cell types in naked viruses.
viral capsid
Viral capsids typically are composed of repeating structural subunits referred to as?
capsomeres
The most common capsid struc- tures geometrically form a?
helical or icosahedral structure
The _______ is responsible for viral entry into the host cell
Lipid envelope
Inserted into this viral envelope are viral proteins, such as(3)
hemagglutinin (HA), neuraminidase, or glycoprotein spikes
assist in stabilization of at- tachment for the lipid envelope and for attachment to the host cell to facilitate viral entry
glycoprotein spikes
Some enveloped viruses also contain a _______ that lies between the envelope and the nucleocapsid.
matrix protein
Viruses that cause disease in humans range from approximately?
20 to 300 nm
Even the largest viruses, such as the _______, cannot be detected with a light microscope, because they are less than one fourth the size of a staphylococcal cell
poxviruses
The _________ improved magnification (more than 100,000 times) allowed visualization of virus particles and paved the way for viral classification based on structural components.
electron microscope’s
____ is determined by the International Commit- tee on Taxonomy of Viruses (ICTV) of the Virology Division of the International Union of Microbiological Societies.
Viral taxonomy
For simplicity purposes, many texts limit viral classification to three basic properties:
(1) viral morphology; (2) method of replication, including genome organization (whether the genome is RNA or DNA and single- or double-stranded); and (3) presence or absence of a lipid envelope.
The phrase_______ refers to the strategy the virus uses to duplicate the viral genome.
“means of replication”
The six steps of virus replication, called the _______
infectious cycle
The six steps of virus replication, called the infectious cycle, proceed as follows?
- Attachment
- Penetration (also referred to as virus entry)
- Uncoating
- Macromolecular synthesis
- Viral assembly
- Release
It involves recognition of a suitable host cell and specific binding between viral cap- sid proteins (often the glycoprotein spikes) and the car- bohydrate receptor of the host cell.
Attachment, also referred to as adsorption
is the process by which viruses enter the host cell.
Penetration (also referred to as virus entry)
occurs once the virus has been internalized. It is the process by which the capsid is removed
Uncoating
involves the production of nucleic acids and protein polymers.
Macromolecular synthesis
is the process by which structural pro- teins, genomes, and in some cases viral enzymes are as- sembled into virus particles.
Viral assembly
is the final step in viral assembly.
Acquisition of an envelope
______ of intact virus particles occurs after cell lysis (lytic virus) or by virus particle budding from cytoplasmic membranes.
Release
Influ- enza viruses, which are released by budding with minimal cell destruction, can be detected in cell culture by an alter- native technique called?
hemadsorption
Viral infections may produce one of three characteristic clinical presentations:
(1) acute viral infection, displaying evident signs and symptoms; (2) latent infection, which has no visible signs and symptoms, but the virus is still present in the host cell in a lysogenic state (inserted into the host genome in a rest- ing state) or maintained as a nuclear or cytoplasmic epi- some; and (3) chronic or persistent infection, in which low levels of virus are detectable and the degree of visible signs or symptoms varies.
After viral infection at a local, often mucosal site, _______ may occur (viruses disseminated in peripheral blood), which may serve to inoculate secondary target tissues dis- tant from the primary site of infection.
viremia
Secondary viremia may occur through
Local mucosal site ➡️ viremia ➡️ skin, salivary glands, kidneys, brain, and other central nervous system (CNS) tissues including the meninges ➡️ symptoms
Disease resolves when specific _______ and ______ prevent continued replication, spread of the virus, and associated host immune responses (i.e., inflamma- tion).
antibody and cell-mediated immune mechanisms
Most DNA-containing viruses, such as those in the ______ group, remain latent in host tissues with no observable signs or symptoms of disease.
herpes- virus
Retroviruses and most DNA viruses establish a latent state after?
primary infection.
Occasionally, pathogenic viruses stimulate an immune reaction that cross-reacts with antigenically similar compo- nents of the host tissues, resulting in impairment to host function; this is called?
autoimmune pathogenesis
In some cases, viral infection can promote _____ or ______ of host cells through expression of specific viral proteins that affect the cell cycle, ultimately resulting in dysregulation or uncontrolled cell proliferation.
transformation or immortalization
Viruses with the ability to stimulate uncontrolled growth of host cells are referred to as?
oncogenic viruses (also known as oncoviruses)
Several high-risk subtypes of ________are oncogenic and are responsible for dysregulation of normal epithelial differentiation leading to cervical cancer.
human papillomavirus (HPV)
In some, antibody produced in response to the measles infection cross reacts with
tissue in the CNS, causing a?
post-infectious encephalitis
In some, antibody produced in response to the measles infection cross reacts with
tissue in the CNS, causing a post-infectious encephalitis. In others, slow but continuing replication of damaged virus in
the brain gives rise to?
subacute sclerosing panencephalitis
Viruses of human medical importance
comprise __ orders, ___ families, ___ subfamilies, and ___ genera
Viruses of human medical importance
comprise 4 orders, 25 families, 13 subfamilies, and 66 genera
viruses that can cause encephalitis
include
HSV, many arboviruses, rabies virus, HIV, measles
virus, and others
HSV also can cause
pharyngitis, genital infection, conjunctivitis, and encephalitis
Standard precautions and Biosafety Level ____conditions are needed for community and most nonretroviral laboratories.
2
Some viruses should not be propagated
in Biosafety Level _____ laboratories because of the risk of accidental exposure and lack of effective therapies, including
influenza H5N1, SARS coronavirus, hemorrhagic fever
viruses, and smallpox
2
Specimen selection depends on the (3)
specific disease syndrome, viral agents suspected, and time of year
aseptic meningitis, caused by infection with various types of enterovirus, may be identified by detecting virus in the? (3)
throat, on a rectal swab, or in cerebrospinal fluid (CSF)
Specimens for the detection of virus should be collected
as early as possible after the?
onset of symptomatic disease
Virus may no longer be present as early as _____ after the
appearance of symptoms
2 days
Virus may no longer be present as early as 2 days after the
appearance of symptoms. However, other factors, such as
the patient’s (3) may play a role in the
length of time viral shedding is evident, allowing effective
laboratory detection.
immune status or age, the type of virus, and the
amount of systemic involvement,
Certain viruses, such as _____, produce a brief, low viremia and undetectable levels at
the onset of symptoms.
West Nile virus
______ swabs interfere with PCR, the
recovery of some enveloped viruses, and fluorescent-antibody
tests and therefore should not be used.
Calcium alginate
In general, ________ are superior to throat or
nasopharyngeal swabs for recovering viruses; however, swabs
are considerably more convenient
nasopharyngeal aspirates
_______ are acceptable for the recovery of enteroviruses, adenoviruses, and
HSV, whereas _________ specimens
are preferred for the detection of RSV and influenza and parainfluenza viruses.
Throat swabs; nasopharyngeal swab or aspirate
Rhinovirus detection requires what specimen
nasal specimen
Throat specimens are collected with a dry, sterile
swab by passing the swab over the (3) areas on the posterior pharynx
inflamed, vesiculated, or purulent
Nasopharyngeal secretion specimens are collected by inserting a swab with a __________ through the nostril into the _______ or by washing and collecting the secretions by rinsing with a bulb syringe and ______ of buffered saline
flexible shaft; nasopharynx; 3 to 7 mL
All respiratory specimens are acceptable for culture of
most viruses. However, respiratory and oral samples often
are contaminated with bacteria. Contaminants may be removed by concentrating the sample through (2)
centrifugation or filtration
However, respiratory and oral samples often
are contaminated with bacteria. Contaminants may be removed by concentrating the sample through centrifugation or filtration. However, this process may also result in ______ of virus-infected cells and reduce the recovery of viral
agents from the sample.
removal
______ and ______ collected during bronchoscopy
are excellent specimens for detecting viruses that infect the lower respiratory tract, especially influenza viruses and adenoviruses.
Washings and lavage fluid
_____ and ______ specimens are used to detect
rotavirus, enteric adenoviruses (serotypes 40 and 41), and enteroviruses.
Stool and rectal swabs of fecal
Many agents of _____________ do not
grow in cell culture and require PCR or electron microscopy for detection
viral gastroenteritis
In general, ______ specimens are preferable to rectal swabs and should be required for rotavirus and enteric adenovirus testing
stool
______ swabs are acceptable for detecting enteroviruses
in patients suspected of having an enteroviral disease, such
as aseptic meningitis
Rectal
The rectal swab is inserted ________
into the rectum and rotated against the mucosa to obtain feces.
3 to 5 cm
________ milliliters of freshly passed
diarrheal stool or stool collected in a diaper from young infants is sufficient and preferred for rotavirus and enteric adenovirus detection.
Five to ten
Urine: Improved recovery results with a minimum specimen volume of ______ from a clean-catch first-morning urine (also known as first-void urine)
10 mL
Urine: Improved recovery results with a minimum specimen volume of 10 mL from a?
clean-catch first-morning urine (also known as first-void urine).
Urine: Virus recovery is improved by ______ or _______ to remove contaminants and neutralizing the pH with a _____ solution of sodium bicarbonate
centrifugation or filtering; 7.5%
Enteroviruses, HSV, VZV, and in rare cases CMV or pox viruses can be detected in _______ lesions of the skin and mucous membranes.
vesicular
Once the vesicle has ulcerated or crusted, detection of the virus is ______.
difficult
Collection of specimens from cutaneous vesicles for detection of HSV or VZV may require a ________ if PCR testing is not available
Tzanck smear
_____ smears are prepared by
carefully unroofing the vesicle
Tzanck
Sterile body fluids, especially (3), may contain enteroviruses, HSV, VZV, influenza viruses, or CMV
CSF and pericardial and pleural fluids
Viral culture of _____ is used primarily to detect CMV;
however, HSV, VZV, enteroviruses, and adenovirus occasionally may be encountered.
blood
(3) anticoagulated blood is acceptable for
CMV detection.
Heparinized, citrated, or ethylenediaminetetraacetic acid (EDTA)
______ blood should be used when other
viruses are being considered
Citrated
_______ should be used for samples collected for nucleic acid testing, because other anticoagulants may interfere with the enzyme functions required
for PCR amplification.
EDTA
Serum may be used for ______ and ________
serologic tests and nucleic acid assays
Bone marrow for virus detection should be added to a sterile tube with?
anticoagulant
Bone marrow for virus detection should be added to a sterile tube with anticoagulant. (3) anticoagulants are acceptable
Heparin, citrate, or EDTA
Except for _______, most viruses are detected
more readily from sites other than bone marrow.
parvovirus B19
______ specimens are especially useful for detecting viruses that
commonly infect the lungs (CMV, influenza virus, adenovirus, sin nombre virus), brain (HSV), and gastrointestinal tract
(CMV).
Tissue
______ specimens often are required for detection of HSV and human papillomavirus (HPV).
Genital
_____ and ____ serum specimens may be needed to detect antibody to specific viruses.
Acute and convalescent
Serum for Antibody Testing: _______ specimens should be collected as soon as possible after the appearance of symptoms.
Acute
Serum for Antibody Testing: The
convalescent specimen is collected a minimum of ______
after the acute specimen.
2 to 3 weeks
Specimens for viral isolation should not be
allowed to sit at____ or _____ temperature.
room or higher
Specimens should be kept ______ at _______ and immediately transported to
the laboratory
cool (4°C)
If a delay in transport is unavoidable, the
specimen should be _____ and _______, until processed.
refrigerated, not frozen
Under unusual circumstances, specimens may need to be held for several days before processing. For storage up to 5 days, specimens are held at _____.
4°C
Under unusual circumstances, specimens may need to be held for several days before processing. Storage for 6 days or longer should be at
______, preferably at ______.
–20°C, preferably –70°C
Specimens for freezing should
first be _____ or ______ in viral transport medium.
diluted or emulsified
Specimens for processing using commercial reagents that are not
approved by the U.S. Food and Drug Administration (FDA),
such as analyte-specific reagents or assays that have been
created and validated in the user’s laboratory (laboratory developed tests [LDTs]), are transported and stored at _______ temperatures.
refrigeration
Specimens for processing using commercial reagents that are not
approved by the U.S. Food and Drug Administration (FDA),
such as analyte-specific reagents or assays that have been
created and validated in the user’s laboratory (laboratorydeveloped tests [LDTs]), are transported and stored at refrigeration temperatures. Freezing at –70°C is recommended if
processing is delayed for longer than _____.
2 to 3 days
Many types of specimens for the detection of virus can be
collected with a swab. Most types of synthetic swabs, such as
_____ and _____, are acceptable.
rayon and Dacron
Once collected,
specimens on swabs should be _______ in viral transport
medium before transport to the laboratory, especially if
transport will occur at room temperature and requires longer than ______.
emulsified; 1 hour
________ is not acceptable for the
culture-based detection of HSV, because it may inactivate
the virus.
Calcium alginate
Also, as previously mentioned, it is not recommended for PCR amplification of any?
respiratory viruses
Commercially prepared transport media are useful for
maintaining ________
viral stability
Transport media contain protein
(e.g., serum, albumin, or gelatin) to ________ the viral agents and antimicrobials to ________ overgrowth of bacteria and fungi.
stabilize; prevent
Transport media contain protein
(e.g., serum, albumin, or gelatin) to stabilize the viral agents
and antimicrobials to prevent overgrowth of bacteria and
fungi. ______ (500 units/mL) and _______ (500-
1000 mg/mL) have been used traditionally; however, a more
potent mixture is composed of _______ (20 mg/mL),
_______ (50 mg/mL), and ______ (10 mg/mL).
Penicillin; streptomycin
vancomycin; gentamicin; amphotericin
If
serum is added as the protein source, _______ serum is recommended, because it is less likely to contain inhibitors,
such as antibodies.
fetal calf
Examples of successful transport media
include? (5) and the commercially available (3)
Stuart’s medium; Amie’s medium; Leibovitz-Emory
medium; Hanks’ balanced salt solution (HBSS); Eagle’s tissue culture medium;
M4, M5, and universal transport media.
Respiratory and rectal
and stool specimens can be maintained in modified (3) containing antimicrobials.
Stuart’s medium, modified HBSS, or Leibovitz-Emory medium
Blood for viral culture, transported in a sterile tube
containing anticoagulant, must be refrigerated at _____ until
processed.
4°C
Testing for virus specific IgM should be completed before freezing whenever
possible, because IgM may form insoluble aggregates upon
thawing, producing a _______ result.
false-negative
