Viruses & Infections Flashcards
What is another name for viruses
Obligate intracellular parasite as they grow only within cells
Can you use antibiotics on viruses
No, because they use our bodies machinery. For an antibody to work it needs to bind to something so it would be binding to our own body and attacking it.
How do viruses infect
They float around and when in contact with the appropriate cell, they invade it and start replicating
Do viruses release enzymes
No, except a few, or toxins
How do viruses cause disease
Due to their destruction off cells rather than toxin releasing
Viral morphology
nucleic acids (genetic material), capsid/covering, envelope
What does the nucleic acid look like inside a virus
It is either DNA or RNA, never both
There is a (+) RNA and (-) RNA. (+) RNA can enter directly into ribosomes and translate into protein molecules. (-) RNA needs to be transcribed into (+) RNA before it can be translated
What is a retroviral RNA
transcribed into DNA using a unique enzyme called reverse transcriptase
RNA -> DNA
Capsids
Geometric shapes with flat surfaces. Helical capsids are long rods that may be rigid or flexible
Envelope
Covers the capsids (outer layer) only sometimes
Viruses that do not have membranes are referred to as naked or non enveloped
Those with membranes are referred to as enveloped
What is a characteristic that distinguishes the family of a virus
having viridae at the end
How do viruses replicate
Viruses so not reproduce on their own, they have nucleic acids but do not possess a ribosome to make proteins.
They possess no energy or energy producing mechanisms.
They must invade a cell and take over its machinery and use its resources in order to form new viral particles.
The 6 steps of viral replication
- Attachement
- Penetration
- Uncoating
- Synthesis of viral DNA or RNA and proteins
- Maturation
- Release
Explain attachment in viral replication
The virus attaches/adheres to the cell by special receptors on the human cells
Viruses are usually cell specific (each virus have a special target cell)
ex. HIV viruses attacks CD4 helper T cells only. Brazil women prostitutes didn’t have receptors for HIV virus so never got it
Explain penetration in viral replication
Occurs by two types according to the virus itself
- Endocytosis for non-enveloped viruses
- Fusion for enveloped viruses
Explain uncoating in viral replication
The protein capsid of the virus separates from the nucleic acids
Explain synthesis of viral DNA or RNA and proteins
The viral DNA or RNA replicates inside the nucleus of the host, they also synthesize their proteins by using the cell ribosomes
Explain maturation in viral replication
The new nucleic acids join with the new proteins synthesized to form new viruses
Explain release in viral replication
The mature viruses are released from the cell
- Enveloped viruses are released by budding (hide under membrane) from the plasma membrane taking a part of the cell’s membrane
- Non-enveloped viruses are released by rupturing the host cell
Route of transmission of viruses
1) Enteric viruses
2) Respiratory viruses
3) Zoonosers
4) Arbovirus
5) Sexually transmitted
Enteric viruses
transmitted by oral route, enter the intestinal tract where they replicate and cause gastroenteritis
Respiratory viruses
Transmitted by inhaling infected droplets and replicate in the respiratory tract: influenza viruses, maps, measles
Zoonosers
Transmitted by animals: rabies
Arboviruses
Transmitted by mosquitoes, ticks, and flies
Sexually transmitted viruses
HIV, Herpes, Hepatitis
What type of virus causes sore throat and conjunctivitis
Adenoviruses
What virus causes influenza
orthomyxoviruses
What virus causes HIV
retrovirus
What virus causes chickenpox, shingles, herpes
Herpesviruses
What virus causes warts
papovaviruses
What virus causes viral hepatitis
hepadnaviruses
How do viruses gain access to cells
Because they have attachment sites for cellular receptors
Do viruses cause allergic reaction
no
What happens when viruses leave our cells
They leave a nucleic acid within our genetic material, this leads to pathologic modifications of the cell’s properties
When this happens the cells should undergo apoptosis, if this doesn’t happen it will likely lead to cancer
The release of non enveloped viruses leads to
The rupture and lysis of cells
What are cytopathic effects (CPE) of Viruses
The effect of Viral infections
two types
used to diagnose many viral infections
Cytocidal effect
When the effect results in cellular death
Non-cytocidal effect
The effect results in cell damage/loss of function but not cell death
CPE effects
Inhibit protein synthesis and mitosis of cells (Herpes virus)
Changes in infected cell’s function with no visible changes in its shape. Ex. an infected hormone secreting cell will not be able to secret hormones anymore
Inducing chromosomal abnormalities that can be malignant
What is autolysis
When a cytocidal virus infects a cell, It causes the cell’s lysosomes to release their enzymes leading to autolysis
Synctium
At times, several adjacent infected cells fuse to form a very large cell.
Inclusion bodies
Are intracellular granules whose presence is a result of viral infection (useful for the identification of some viral infections)
Influenza virus types
A, B, and C
What type of influenza is typically associated with pandemics and wide-spread epidemics
Type A
Symptoms of influenza
A specific acute viral respiratory infection with fever, chills, headache, cough, nasal discharge, sometimes causing bronchitis, pneumonia, and death in severe cases
Rare nausea, vomiting, and diarrhea
Morphology of influenza virus
Influenza virus particles are highly pleomorphic, mostly spherical/ovoid, but many forms occur, including long filamentous particles
High levels or mutations, because it can’t catch mutations in DNA/RNA replications
Explain the outer surface of the influenza virus
Consistis of a lipid envelope from which project prominent glycoprotein spikes of two types:
Hemagglutinin (HA), and
Neuraminidase (NA)
Hemagglutinin (HA)
HA is considered a ligand it helps enter by binding to a receptor
HA needs to be in a certain shape to attach
Neuraminidase (NA)
Helps exit and infect other cells
What determines if influenza virus is going to affect us humans
Hemagglutinin (HA), and Neuraminidase (NA) (glycoproteins) they are basically spikes on the outer surface of the virus
Who does influenza A viruses infect
a wide variety of mammals, including man, horse, pigs, ferrets, and birds (reassortment)
Who does influenza B viruses infect
Man and birds
Causes human disease
Epidemiologically important
Who does influenza C viruses infect
Man alone
Do not cause disease
They are genetically and morphologically distinct from A and B types
Pathogenesis of influenza virus
the spread is by aerosols-very efficient
What does the primary infection of influenza virus involve
Primary infection involves the ciliated epithelial cells of the URT
Normally self-limited infection usually lasts 3-7 days (+ convalescence)
Damage to respiratory epithelium predisposes to secondary bacterial infections which accounts for most death
What is the virus that causes Covid-19
SARS-CoV-2 (severe acute respiratory syndrome coronavirus)
How many strains of coronavirus are there
7 strains (mostly symptoms similar to colds)
How long is the incubation period for Covid-19
14 days, maidan of 4-5 days
Most common symptoms of Covid-19
cough (86%), fever or chills (85%), and shortness of breath (80%), diarrhea (27%), and nausea (24%)
sputum production, headache, dizziness, rhinorrhea
anosmia (loss of sense of smell)
dysgeusia (changes in sense of taste)
sore throat, abdominal pain, anorexia and vomiting
Can you receive antibiotics if you have a virus and bacteria
Yes
How is COIVD-19 spread
Respiratory droplets
Severe manifestations/complications of COVID-19
Pneumonia
Actue respiratory distress syndrome (ARDS)
Multi Organ Failture
Inflammatory response moves to other parts of the body Systemic inflammatory response syndrome (SIRS): inflammation in every organ
Septic shock (decrease in BP)
Cytokine Storm
Death
Pathopphysiology od COVID-19 virus
Virus binds with angiotensin converting enzyme 1 (ACE-2) on the Type II pneumoncytes (produce surfactant) in alveoli of lungs
Virus replicates, destroys type II pneumocyte and leads to inflammation
Leads to more blood supply and vasodilation and increased permeability
Fluid moves into interstitial apace around alveoli
Less room for gas exchange (decrease O2)
Increase in breathing (dyspnea)
Is COVID-19 in the upper or lower tract
upper but pneumonia is in lower
What type of microorganism is fungi
aerobic eukaryotic
obligate parasites because they cannot make their own food
Saprophytes (decomposers)
Live on decomposing dead organisms
Thus help get rid of dead bodies and turning to mineral salts
What can fungi tolerate well
High concentrations of salts, sugars, and acids
Are bacteria or fungi normally responsible for spoilage of food
Fungi
What type of medium to fungi prefer
moist
What range of pH and temp does fungi tolerate
2 to 9 and -6 C to 50 C
What are the 3 major groups of fungi
1) Yeasts
2) Molds
3) Dimorphic fungi
Yeasts structure
Unicellular, oval or cylindrical microorganisms
Larger than bacteria in size
How do yeasts reproduce
by budding
Molds structure
Filamentous multicellular fungi
How do molds reproduce
spores, which spread to form mycelia
How do dimorphic fungi grow
grow as either Yeats or mold depending on the temperature and environmentalconditions
What is the usual temperature that yeast and typically form in our bodies
Yeast - 37 C
Mold - form in soil
What are Fungal cell membranes like
Contains the sterol, ergosterol (compared to cholesterol in human cells)
What part of fungi is the target for most anti fungal drugs
Their cell membrane
What is fungi’s cell wall like
made of chitin (complex of polysaccharide close to cellulose)
Do fungi have a capsule
Some fungi have an antiphagocytic capsule which coats the fungal cell and protects it
Fungal infections in humans (mycosis)
1) Superficial Mycosis
2) Cutaneous Mycosis
3) Systemic Mycosis
Superfical Mycosis
Mild infection of the epidermal layer characterized by pigment change of the skin
Ex. Tinea versicolor & Tinea nigris
Where does cutaneous Mycosis occur
Located at the epidermis, hair follicles or nails
What are the manifestations of cutaneous mycosis
Scaling, crumbling of nail, and loss of hair
Ex. Tinea infections
What is systemic mycosis caused by
dimorphic fungi and not contagious
What happens when spores are inhaled in systemic mycosis
Fungi live as mycelia in nature and release spores to the atmosphere
They grow as yeast cells and infect the lung
this is followed by blood stream dissemination and in most cases the fungus is destroyed at this point
What are systemic mycosis
It is a deep fungal infection that affects many organs and tissues
what symptoms does systemic mycosis cause
Can be asymptomatic, mild pneumonia, or severe tuberculosis-like infections
What does candidiasis cause
Infection caused by Candida albicans yeast in normal host it causes cutaneous infections in the mouth and vagina
In immunocompromised patients candidiasis is disseminated to almost all organs
Aspergillosis
It is a mild infection caused by spores of Aspergillus flakes mold
The spores float in the air and develop asthma type reaction
In immunocompromised, aspergillosis is severe and leads to liver damage
Fungal mechanisms of pathogenicity
These do not have a well defines set of virulence factors
Some fungi have metabolic products that are toxic to human host
May provoke an allergic reaction
Enzymes produces by some fungi such as proteases and keratinases (mainly superficial fungi)
