Viruses and virology:
-Viruses are infectious particles that must have a living host cell that they "hijack" in order to replicate
-Virus particles are called virions
-Viruses cannot be seen with the naked eye or with the light microscope, so they must be viewed with a Transmission Electron Microscope
-Virions consist of nucleic acid (DNA or RNA) surrounded by a protective protein capsid made up of individual, spherical capsomers (protein subunits), which are encoded by the viral genome
-Some virions, but not all, have a lipid envelope made of the host cell membrane
-Morphological distinction is based on the shape and size of the virion, the type of nucleic acid (DNA or RNA) and if it has an envelope or not. Shapes may be:
Helical
Icosahedral
Prolate
Enveloped
Complex
-Viral assembly occurs spontanenously when encoded protein subunits (capsomers) self-assemble to form a capsid, which requires first the presence of a viral genome (DNA or RNA)
-The genome of viruses changes so frequently they are subject to many mutations. Genetic change occurs by the following processes:
-Antigenic Shift-This type of change occurs when there is a major change to the genetic material of the virus via genetic recombination or reassortment. This type of change occurs with viruses such as the influenza virus and avian influenza virus or swine flu. When this occurs, pandemics may occur.
-Antigenic Drift-Individual bases in the DNA or RNA of the virus mutate to other bases (point mutations). It is because of these mutations that vaccinations such as the "Flu Shot" must be altered a little and changed a little each year to account for these mutations.
VIRAL INFECTION:
Viral infection occurs via the following steps:
VIRAL LATENCY:
Some viruses can develop a latent state, in which they migrate into the nerves of the sensory ganglia and stay there for life. During times of immunocompromisation or illness, they may become reactivated, resulting in a relapse of infection. An example of this is the Varicella-Zoster Virus. After an initial infection of Chicken Pox (Varicella), the virus travels to the sensory ganglia where it remains dormant, but may become activated once again during times of exhaustion, illness, stress, the menstrual cycle, anxiety, fever, exposure to sunlight, weakening of the immune system, chronic disease, immunocompromisation, or in the elderly, resulting in a case of the Shingles (Zoster). Migration of the virus out to the peripheral skin through the nerve endings causes local destruction and the formation of fluid-filled vesicles/blisters and burning pain.
TYPES OF VIRUSES:
1) DNA VIRUSES: DNA replication occurs in the host cell's nucleus
-Viruses cause a whole array of various side effects in the host, depending upon the type of virus and the environmental factors
-Viruses may be cultured in viral medium, in continuous cell lines such as HeLA cells, in shell vials, and viewed microscopically with fluorescent stains for identification
-Virus particles are called virions
-Viruses cannot be seen with the naked eye or with the light microscope, so they must be viewed with a Transmission Electron Microscope
-Virions consist of nucleic acid (DNA or RNA) surrounded by a protective protein capsid made up of individual, spherical capsomers (protein subunits), which are encoded by the viral genome
-Some virions, but not all, have a lipid envelope made of the host cell membrane
-Morphological distinction is based on the shape and size of the virion, the type of nucleic acid (DNA or RNA) and if it has an envelope or not. Shapes may be:
Helical
Icosahedral
Prolate
Enveloped
Complex
-Viral assembly occurs spontanenously when encoded protein subunits (capsomers) self-assemble to form a capsid, which requires first the presence of a viral genome (DNA or RNA)
- HELICAL VIRUSES: These viruses are composed of a single type of capsomer that stack up around a central axis, cavity or tube. This is what forms the helical structure. These viruses appear filamentous or rod-shaped. They range from short-to-long, and rigid-to-flexible. The genetic material inside is either ssRNA (more common) or ssDNA (rare). Inside, the genetic nucleic acid material possesses a negative charge, whereas the proteins surrounding the genome (capsomer/capsid) possess a positive charge. An example of this type of virus is the Tobacco Mosaic Virus (TMV) as seen in the images below.
- ICOSAHEDRAL VIRUSES: These viruses are symmetric hexamers or pentamers that have a unique structure and design to them. Identical protein subunits form the closed shell capsid surrounding the genome. There are at least 12 identical capsomers, each of which are composed of 5 identical subunits. Some viruses even have more than 12 capsomers, and may appear more spherical than icosahedral in shape. At the apices of the particle, capsomers are surrounded by 5 other capsomers. These are called pentons (curved). On the triangular faces of the icosahedran, capsomers are surrounded by 6 other capsomers. These are called hexons (flat). Examples of these types of viruses include Adenovirus and Rotavirus, shown in the images below.
- PROLATE: This type of arrangement forms the head of a bacteriophage, and is basically an elongated icosahedron.
- ENVELOPED VIRUS: Some, but not all, viruses have a lipid envelope that they acquire from the cell membrane of the host cell during the final stages of exocytosis. Influenza Virus, HIV Virus, and Cytomegalovirus (CMV) are examples of enveloped viruses, which are dependent upon this envelope for their infectivity.
- COMPLEX: The capsid of these viruses is complex, in that in does not have a definite shape. The virus particle is not truly helical, nor is it truly icosahedral in structure. Some bacteriophages possess this structure.
-The genome of viruses changes so frequently they are subject to many mutations. Genetic change occurs by the following processes:
-Antigenic Shift-This type of change occurs when there is a major change to the genetic material of the virus via genetic recombination or reassortment. This type of change occurs with viruses such as the influenza virus and avian influenza virus or swine flu. When this occurs, pandemics may occur.
-Antigenic Drift-Individual bases in the DNA or RNA of the virus mutate to other bases (point mutations). It is because of these mutations that vaccinations such as the "Flu Shot" must be altered a little and changed a little each year to account for these mutations.
VIRAL INFECTION:
Viral infection occurs via the following steps:
- Attachment-Host cells contain various receptors on the cell membrane. Virus particles utilize their capsid proteins to find and bind to these receptors so that they can get into the host cell for replication and use the host cell machinery for this purpose to produce copies of themselves. Once binding occurs via one or more viral proteins to host cell receptors, this causes the host cell membrane and the viral membrane to undergo changes that induce the fusion of the viral and host cell membranes, allowing the virus to enter.
- Penetration-Membrane fusion, or receptor-mediated endocytosis, welcomes the virus into the host cell. This is the viral entry process. Some viruses inject their genetic material directly into the host cell, while the capsid actually remains outside the cell. Bacteriophages are an example.
- Uncoating-Once inside the host cell, the viral capsid is removed and broken down by viral enzymes carried into the cell, host enzymes, or dissociation and falling apart of the capsid on its own. Viral genome nucleic acid (DNA or RNA) is released into the host cell.
- Replication-At this stage, the viral genome is copied and multiplied. Viral messenger RNA (mRNA) is synthesized and viral proteins are synthesized and assembled.
- Assembly-At this stage, the newly synthesized viral proteins begin to self-assemble around the copied/replicated viral genetic material. The proteins are modified if need be in some viruses, whereas in other viruses, modification or maturation occurs after the new virion is released from the host cell.
- Release-Once the host cell is filled up with new virions (100-200), it bursts or lyses, releasing the new virions to go and infect new host cells. This kills the host cell and the contents are released. Enveloped viruses acquire their envelope by budding and released by budding.
VIRAL LATENCY:
Some viruses can develop a latent state, in which they migrate into the nerves of the sensory ganglia and stay there for life. During times of immunocompromisation or illness, they may become reactivated, resulting in a relapse of infection. An example of this is the Varicella-Zoster Virus. After an initial infection of Chicken Pox (Varicella), the virus travels to the sensory ganglia where it remains dormant, but may become activated once again during times of exhaustion, illness, stress, the menstrual cycle, anxiety, fever, exposure to sunlight, weakening of the immune system, chronic disease, immunocompromisation, or in the elderly, resulting in a case of the Shingles (Zoster). Migration of the virus out to the peripheral skin through the nerve endings causes local destruction and the formation of fluid-filled vesicles/blisters and burning pain.
TYPES OF VIRUSES:
1) DNA VIRUSES: DNA replication occurs in the host cell's nucleus
- Single- or double-stranded
- Single or segmented pieces
- Genome complexity
- Herpesviridae
- Hapadnaviridae
- Adenoviruses
- Papovaviruses
- Parvoviruses
- Poxviridae
- Single- or double-stranded
- Single or segmented pieces
- Positive (+) OR Negative (-) stranded RNA
- Genome complexity
- Most are single-stranded
- Half are positive (+) stranded
- Togaviridae
- Coronaviridae
- Retroviridae
- Picornaviridae
- Caliciviridae
- Reoviridae
- Orthomyxoviridae
- Paramyxoviridae
- Rhabdoviridae
- Bunyaviridae
- Arenaviridae
- Filoviridae
- Astroviridae
-Viruses cause a whole array of various side effects in the host, depending upon the type of virus and the environmental factors
-Viruses may be cultured in viral medium, in continuous cell lines such as HeLA cells, in shell vials, and viewed microscopically with fluorescent stains for identification
viral antigenic drift versus antigenic shift, new strains, epidemics, pandemics:
overview of viral infections:
cytopathic effect and formation of syncytia:
Cytopathic effect is cellular destruction caused by a virus. It results in separation of the epithelium. Cells become multinucleated giant syncytial cells that have intranuclear inclusion bodies. This can be detected by viral cell culture in a monolayer, then by dying the cells with iodine or with fluorescence staining. Microscopic studies reveal multinucleated giant cells and intranuclear inclusion bodies. These are thought to form once viral proteins are inserted into the host cell plasma membranes, resulting in cellular fusion and the formation of multinucleated giant cells. The intracellular inclusions are thought to be areas of viral assembly.
staining viral cells:
An enveloped virus particle:
non-enveloped virus particles, virus morphology and classification:
capsids:
Capsids are the protein shell that encapsulates the strands of RNA or DNA. There are two types:
- Icosahedral
- Capsomers arranged into an equilateral triangle
- 20 triangles together to form an icosahedron
- Helical
- Protein capsomers are bound to RNA coiled into a helical nucleoprotein capsid
- Spherical shape (other than rhabdoviruses, which are bullet-shaped)
- Enveloped
- A lipid bilayer membrane covering some capsids
- Acquired through budding through the host cell nuclear or cytoplasmic membrane
- Non-enveloped
- Bare capsid without a lipid membrane
viral chromosome:
dna viruses:
When it comes to DNA viruses, DNA is unable to be directly translated into proteins, rather it must first be transcribed into mRNA, and then translated into structural proteins and enzymes.
DNA viruses have BOTH a negative strand AND a positive strand.
- The positive strand of DNA
- Is the one that is being READ
- Serves as a template for transcription into mRNA
- Is "proofread" by DNA polymerase enzyme
- The negative strand of DNA
- Is the one that is NOT being read
Poxviruses:
Variola Virus (Smallpox)
Vaccinia Virus (Cowpox)
Orthopoxvirus (Monkeypox)
Molluscum contagiosum (Water Warts)
MONKEYPOX:
Monkeypox virus has caused epidemics in the past, but there is a new outbreak in 2022, and is spreading across the globe slowly as of July, 2022. This is closely tracked by the CDC and the WHO, who monitors, records and studies the patterns. This rare disease is caused by infection with the monkeypox virus. It is not related to chicken pox, however, it is in the same family as variola virus, the virus that causes smallpox, and vaccinia virus (used as a vaccine against smallpox).
1958 was the year when monkeypox was first discovered in a couple of monkey colonies that were being kept and observed for research. The original source or index case remains unknown, but it is thought that African rodents and monkeys may harbor the virus that causes disease in primates and humans. The first human case was not discovered until 1970, at which time it occurred and has since occurred a couple of times in central and west Africa. Prior to the current outbreak in 2022, nearly all cases were tied to international travel to countries where the disease is endemic, or to importing of infected animals from those endemic areas.
The west African strain of monkeypox is rarely ever fatal, and the <1% of people who are at risk for complications and fatality include those who are severely immunocompromised or those who are young or elderly. Those who are pregnant, breastfeeding, or have chronic eczema are also at higher risk for complications due to the disease. The symptoms can be painful, itch, and leave permanent scarring. The most common symptoms are as follows:
The risk for monkeypox in the USA remains low. It is not spread easily from person-to-person. It has a rather long incubation period, so this is good in that it gives epidemiologists and researchers more time to track the infection, index case(s) and try to break the chain of infection. Only those experiencing symptoms can actually spread the disease. Those without any symptoms cannot spread the disease. When one has been positively diagnosed, they should remain isolated until the scabs fall off, the rash has healed, and a fresh layer of intact skin has replaced the rash.
Though it does not spread easily, there are several means of transmission:
Vaccinia Virus (Cowpox)
Orthopoxvirus (Monkeypox)
Molluscum contagiosum (Water Warts)
MONKEYPOX:
Monkeypox virus has caused epidemics in the past, but there is a new outbreak in 2022, and is spreading across the globe slowly as of July, 2022. This is closely tracked by the CDC and the WHO, who monitors, records and studies the patterns. This rare disease is caused by infection with the monkeypox virus. It is not related to chicken pox, however, it is in the same family as variola virus, the virus that causes smallpox, and vaccinia virus (used as a vaccine against smallpox).
1958 was the year when monkeypox was first discovered in a couple of monkey colonies that were being kept and observed for research. The original source or index case remains unknown, but it is thought that African rodents and monkeys may harbor the virus that causes disease in primates and humans. The first human case was not discovered until 1970, at which time it occurred and has since occurred a couple of times in central and west Africa. Prior to the current outbreak in 2022, nearly all cases were tied to international travel to countries where the disease is endemic, or to importing of infected animals from those endemic areas.
The west African strain of monkeypox is rarely ever fatal, and the <1% of people who are at risk for complications and fatality include those who are severely immunocompromised or those who are young or elderly. Those who are pregnant, breastfeeding, or have chronic eczema are also at higher risk for complications due to the disease. The symptoms can be painful, itch, and leave permanent scarring. The most common symptoms are as follows:
- Headache
- Fever
- Myalgia (muscle and back pain)
- Lymphodenopathy (swollen lymph nodes)
- Fatigue and exhaustion
- Chills
- Rash (resembles pimples or blisters that typically start on the face and spread to the inside of the mouth, body, hands, feet, chest, genitals, and/or anus), going through different stages before healing, and lasting 2-4 weeks
The risk for monkeypox in the USA remains low. It is not spread easily from person-to-person. It has a rather long incubation period, so this is good in that it gives epidemiologists and researchers more time to track the infection, index case(s) and try to break the chain of infection. Only those experiencing symptoms can actually spread the disease. Those without any symptoms cannot spread the disease. When one has been positively diagnosed, they should remain isolated until the scabs fall off, the rash has healed, and a fresh layer of intact skin has replaced the rash.
Though it does not spread easily, there are several means of transmission:
- Direct contact with the scabs, infectious rash, body fluids, respiratory droplets, prolonged face-to-face contact (kissing), intimate physical contact (oral, anal, vaginal sex, hugging, cuddling, massaging, talking closely, sex toys)
- Vertical transmission (pregnant woman can spread it to the fetus through the placenta)
- Indirect contact (touching a fomite, or inanimate object, such as linens, clothing, bedding, that touched the infectious rash or body fluids or scabs)
- From infected animals (bite, scratch, using animal products, touching the fur, eating contaminated meat)
Monkeypox images:
smallpox images:
vaccinia virus images:
molluscum contagiosum images:
Herpesviruses:
Herpes Simplex Viruses 1, 2 (HSV)-
-HSV 1: Produces most cold sores (contagious)
-HSV 2: Produces most genital sores (STD) (contagious)
-Latent: Virus remains in neural ganglia and may cause relapses/reactivation. HSV 1 remains latent in the trigeminal ganglia. HSV 2 remains latent in the sacral ganglia.
Varicella-Zoster Virus (Chickenpox, Shingles) (VZV)
Cytomegalovirus (CMV) (HSV 5)
-Infected cells swell up (cytomegaly)
-Asymptomatic Infection
-Symptomatic Infection (Congenital Disease; most common viral cause of mental retardation; microcephaly, deafness, seizures, multiple birth defects)
-CMV Mononucleosis in young adults (similar to EBV)
-CMV may reactivate if a patient is immunocompromised, resulting in retinitis, blindness, pneumonia, systemic infection, or death
Epstein-Barr Virus (EBV) (Infectious Mononucleosis)
-Associated with transformation into cancerous cells in Burkitt's Lymphoma
Roseolavirus (HHV-6) (6th Disease or Exanthema subitum)
Human Herpes Virus 7 (HHV-7): Roseolavirus
-HSV 1: Produces most cold sores (contagious)
-HSV 2: Produces most genital sores (STD) (contagious)
-Latent: Virus remains in neural ganglia and may cause relapses/reactivation. HSV 1 remains latent in the trigeminal ganglia. HSV 2 remains latent in the sacral ganglia.
Varicella-Zoster Virus (Chickenpox, Shingles) (VZV)
Cytomegalovirus (CMV) (HSV 5)
-Infected cells swell up (cytomegaly)
-Asymptomatic Infection
-Symptomatic Infection (Congenital Disease; most common viral cause of mental retardation; microcephaly, deafness, seizures, multiple birth defects)
-CMV Mononucleosis in young adults (similar to EBV)
-CMV may reactivate if a patient is immunocompromised, resulting in retinitis, blindness, pneumonia, systemic infection, or death
Epstein-Barr Virus (EBV) (Infectious Mononucleosis)
-Associated with transformation into cancerous cells in Burkitt's Lymphoma
Roseolavirus (HHV-6) (6th Disease or Exanthema subitum)
Human Herpes Virus 7 (HHV-7): Roseolavirus
adenoviruses:
Adenoviruses 1-48 (Colds, Upper Respiratory Infections, Diarrhea and Gastroenteritis, Nausea/Vomiting/Headache/Fever/Abdominal Pain)
-Fever lasting 3-4 days
-Viral pharyngitis
-Viral conjunctivitis
-Swollen Glands
-Headache
-Malaise
-Weakness
-Ear infection
-Incubation period: 5-9 days
-Affects mostly ages 5-18
-Spring and Fall most outbreaks, as well as at summer camps
-Often spread through public swimming pools
-May also cause gastroenteritis (types 40, 41)
-May also cause a rash
-May also cause cystitis (bladder infection)
-Complications may include pneumonia, croup, bronchiolitis, or bronchitis, or even Acute Respiratory Disease, viral meningitis, encephalitis, or hemorrhagic cystitis
-Fever lasting 3-4 days
-Viral pharyngitis
-Viral conjunctivitis
-Swollen Glands
-Headache
-Malaise
-Weakness
-Ear infection
-Incubation period: 5-9 days
-Affects mostly ages 5-18
-Spring and Fall most outbreaks, as well as at summer camps
-Often spread through public swimming pools
-May also cause gastroenteritis (types 40, 41)
-May also cause a rash
-May also cause cystitis (bladder infection)
-Complications may include pneumonia, croup, bronchiolitis, or bronchitis, or even Acute Respiratory Disease, viral meningitis, encephalitis, or hemorrhagic cystitis
Papilloma viruses:
Human Papilloma Virus (HPV) (Warts)
JC Virus/Polyomavirus
-Causes Progressive multifocal leukoencephalopathy (PML) in persons with severe immunodeficiency, immunosuppression, or autoimmune disorders. It is rare and typically fatal (30-50%). It causes an inflammation of the white matter of the brain at multiple locations within the brain. Therefore, those that do survive often come out of it with neurological disabilities (memory loss, poor speech, incoordination, dementia).
BK Virus/Polyomavirus
-This disease causes mild or asymptomatic respiratory infection and fever, followed by dissemination to the kidneys and urinary tract where it persists for life. It causes severe illness in the immunocompromised or immunosuppressed.
-May lead to renal dysfunction and need of a transplant
JC Virus/Polyomavirus
-Causes Progressive multifocal leukoencephalopathy (PML) in persons with severe immunodeficiency, immunosuppression, or autoimmune disorders. It is rare and typically fatal (30-50%). It causes an inflammation of the white matter of the brain at multiple locations within the brain. Therefore, those that do survive often come out of it with neurological disabilities (memory loss, poor speech, incoordination, dementia).
BK Virus/Polyomavirus
-This disease causes mild or asymptomatic respiratory infection and fever, followed by dissemination to the kidneys and urinary tract where it persists for life. It causes severe illness in the immunocompromised or immunosuppressed.
-May lead to renal dysfunction and need of a transplant
Hepadnavirus:
Hepatitis B (Acute and Chronic Liver Disease)
-May lead to liver cirrhosis
-May lead to hepatic carcinoma
-May lead to liver cirrhosis
-May lead to hepatic carcinoma
parvovirus:
Parvovirus B-19 (5th Disease)
rna viruses:
There are three types of RNA for RNA viruses:
- Positive stranded RNA
- This is like a mRNA (messenger RNA)
- It enters a host cell and is immediately translated by the host's ribosomes into a protein
- Negative stranded RNA
- Enters a host cell but cannot immediately be translated into a protein because it must first be transcribed into a positive strand first, THEN it can be translated into a protein
- Retrovirus
- RNA is transcribed in a reverse manner into DNA
- The virus carries with it into the human cell an enzyme called reverse transcriptase in order to do this
- Example virus: HIV
orthomyxoviruses:
Influenza A, B, C
Influenza A
Characteristics:
Why do we experience epidemics and pandemics of this virus:
Antigenic Drift
Influenza A
- Infects humans, mammals, swine, birds
- Only isolated from humans
Characteristics:
- Spherical virions
- Contain 8 segments of negative-stranded RNA surrounded by a protein nucleocapsid in a helical shape
- Contains an outer membrane
- Studded with glycoprotein spikes
- Hemagglutinin (HA)
- Attaches to host sialic acid receptors present on the surface of erythrocytes, and present on the cells of the upper respiratory tract cell membranes
- Cause heme-agglutination when mixed with red blood cells
- Activates fusion of virion membrane with host cell membrane so the viral genome can be "dumped" or emptied into the host cell
- Required for adsorption
- Antibodies may block this binding and so prevent infection
- Neuraminidase (NA)
- Mucin (mucous that covers the mucosal epithelial cells) contain neuraminic acid, which is disrupted by the viral enzyme neuraminidase, exposing the sialic acid receptors underneath
- Antibodies can bind here and prevent this from occurring, thereby preventing infection
- M-proteins (anchor the glycoproteins to the viral lipid layer)
- Hemagglutinin (HA)
Why do we experience epidemics and pandemics of this virus:
Antigenic Drift
- During viral replication, mutations occur in the HA or NA
- Antigens within the glycoproteins change, but these changes are small
- New strains result, which are just partially attacked by our immune system
- This is the reason why new vaccines are created each year, based on what the most likely mutations might be, but researchers don't always get it right and have to do the best they can in determining the most likely mutations when developing annual vaccinations, which are not always 100% effective
- Major mutations cause major changes that alter the codon reading frame
- Complete change of the HA, NA or even BOTH
- Occurs only with influenza type A
- Involves trading of the RNA segments between human and animal strains (called "genetic reassortment")
- 2 influenza types can literally co-infect the same cell, rearrange genetic RNA segments, undergo replication and capsid packaging, and mispackage RNA segments into another virus, causing that virion to contain new HA or NA that has never been exposed to the human immune system
- The new HA and NA antigens are given number subscripts to differentiate them
- 1889: H2
- 1900: H3N2
- 1918: Hswine hemagglutinin (HSW); HswN1
- 1989: H2N2
- 1947: H1N1
- 1957: H2N2
- 1968: H3N2
- 1977: H1N1
- The new HA and NA antigens are given number subscripts to differentiate them
- This type causes pandemics, like the big pandemics that have occurred throughout history, as in 1918 (killed 20 million people across the world)
- Pneumonia
- Meningitis/Encephalitis
- Bacterial infections
paramyxoviruses:
Parainfluenza Viruses
-Types 1 and 2 are the most common causes of croup and acute laryngotracheitis in children (75% of cases) and includes fever, sore throat, and an increased WBC
-Types 3 and 4 cause bronchiolitis and pneumonia
Measles (Rubeola)
Mumps
Respiratory Syncytial Virus (RSV)
Human metapneumovirus
-Types 1 and 2 are the most common causes of croup and acute laryngotracheitis in children (75% of cases) and includes fever, sore throat, and an increased WBC
-Types 3 and 4 cause bronchiolitis and pneumonia
Measles (Rubeola)
Mumps
Respiratory Syncytial Virus (RSV)
Human metapneumovirus
- Causes upper and lower respiratory tract infections
- Discovered in 2001
- Affects all ages, but those at highest risk are children, elderly, and the immunocompromised
- Symptoms: cough, nasal congestion, fever, shortness of breath that may progress to bronchitis or pneumonia
- Incubation period: 3-6 days
- Seasonal: late winter and spring
- Transmission: contact and secretions through coughing and sneezing (use droplet/contact precautions)
Togaviruses:
Western Equine Encephalitis
-Primarily seen in states West of the Mississippi River
-Usually subclinical and symptomatic infections are uncommon, but may cause serious illness in infants and children
-Mortality rate is low at just 4% (mostly affects elderly who are infected)
Eastern Equine Encephalitis
-Called Triple E or Sleeping Sickness
-First recognized in MA and more common in the northeastern USA
-The virus is rare, however, the fatality rate is high at 33% at 2-10 days after onset of symptoms
-High fever, muscle pain, altered mental and neurological status, headache, photophobia, meningeal irritation, seizures
-Symptoms appear 4-10 days after the initial mosquito bite
and possible tremors, seizures and paralysis
-Symptoms are either systemic, encephalitic or both and include headache, chills, muscle and joint aches and pains, high fever with brain lesions and sensitivity to sound, restlessness, periods of excitement, drowsiness (malaise), and possible brain swelling (encephalitic type)
-Causes Dengue Fever or "Breakbone Fever"
Protect Yourself From Mosquito-Borne Viruses (Per the CDC):
-Infectious disease that infects the liver
-Asymptomatic at first, but may become chronic
-Acute phase symptomatic in just 15% of people
-Chronic infection may lead to scarring of the liver, cirrhosis, liver failure, liver cancer, or esophageal and gastric varices
-Spread by blood-to-blood contact (contaminated needles, transfusions, poorly sterilized medical equipment, IV drug use)
-The virus remains in the liver of approximately 85% of persons who become infected
-50-80% of people who are treated become cured
-This virus is the leading cause of liver transplant
-There is no vaccine available
-Primarily seen in states West of the Mississippi River
-Usually subclinical and symptomatic infections are uncommon, but may cause serious illness in infants and children
-Mortality rate is low at just 4% (mostly affects elderly who are infected)
Eastern Equine Encephalitis
-Called Triple E or Sleeping Sickness
-First recognized in MA and more common in the northeastern USA
-The virus is rare, however, the fatality rate is high at 33% at 2-10 days after onset of symptoms
-High fever, muscle pain, altered mental and neurological status, headache, photophobia, meningeal irritation, seizures
-Symptoms appear 4-10 days after the initial mosquito bite
and possible tremors, seizures and paralysis
-Symptoms are either systemic, encephalitic or both and include headache, chills, muscle and joint aches and pains, high fever with brain lesions and sensitivity to sound, restlessness, periods of excitement, drowsiness (malaise), and possible brain swelling (encephalitic type)
- Symptoms last 1-2 weeks
- Encephalitic type symptoms will also include: irritability, vomiting, diarrhea, loss of appetite, cyanosis, convulsions, coma
- Those who survive may endure lasting symptoms ranging from moderate to severe and death can even occur years later and may include the CNS
- There is no treatment or vaccination for the virus
- Diagnosis is made by analysis of the CSF and/or brain tissue
- Neutrophilia
- Elevated CSF protein
- Normal CSF glucose
- Evidence of brain lesions at the cortex, midbrain and brainstem
- Detection of EEEV IgM antibodies in serum and CSF
- Neutrophilia
-Causes Dengue Fever or "Breakbone Fever"
Protect Yourself From Mosquito-Borne Viruses (Per the CDC):
- Avoid outdoor activity from dusk til dawn
- Wear mosquito-repellent containing DEET or an organic repellent containing lemongrass or peppermint or lemon-eucalyptus, picaridin, IR3535, para-menthan-diol, or 2-undecanone
- Use citronella candles if you must be outdoors after dusk
- During an active season, if you must be outdoors, wear long pants, long-sleeves and a hat
- Treat your clothing and equipment
- Treat the areas inside and outside your home to prevent mosquitoes
- Avoid keeping containers with long-standing water around, which breeds mosquitoes (planters, birdbaths, etc...)
- Cover baby strollers with protective netting when outdoors with babies and toddlers
-Infectious disease that infects the liver
-Asymptomatic at first, but may become chronic
-Acute phase symptomatic in just 15% of people
-Chronic infection may lead to scarring of the liver, cirrhosis, liver failure, liver cancer, or esophageal and gastric varices
-Spread by blood-to-blood contact (contaminated needles, transfusions, poorly sterilized medical equipment, IV drug use)
-The virus remains in the liver of approximately 85% of persons who become infected
-50-80% of people who are treated become cured
-This virus is the leading cause of liver transplant
-There is no vaccine available
bunyaviruses:
CA and La Crosse Encephalitis
Rift Valley Fever
Hemorrhagic Fevers
Sin Nombre Virus
-Causative agent of Hantavirus Cardiopulmonary Syndrome
-"Four Corners Virus"
-May result in Hemolytic Uremic Syndrome (HUS)
Hantaviruses
-Causative agent of Hantavirus Hemorrhagic Fever With Renal Syndrome
-Causative agent of Hantavirus Pulmonary/Cardiopulmonary Syndrome
-May result in Hemolytic Uremic Syndrome (HUS)
Rift Valley Fever
Hemorrhagic Fevers
Sin Nombre Virus
-Causative agent of Hantavirus Cardiopulmonary Syndrome
-"Four Corners Virus"
-May result in Hemolytic Uremic Syndrome (HUS)
Hantaviruses
-Causative agent of Hantavirus Hemorrhagic Fever With Renal Syndrome
-Causative agent of Hantavirus Pulmonary/Cardiopulmonary Syndrome
-May result in Hemolytic Uremic Syndrome (HUS)
sin nombre' virus:
Hantavirus:
Calciviruses:
Norwalk Virus (Nausea and Vomiting)
-Known as the winter vomiting virus
-Named after Norwalk, OH
-Transmission Contact Precautions: Enteric Contact Precautions
Norovirus (Gastroenteritis and watery diarrhea, Nausea, Projectile Vomiting, Abdominal Pain, Loss of Appetite and Taste, Lethargy, Weakness, Muscle Pain, Headache, Low-Grade Fever)
-Also known as the winter vomiting virus
-The most common cause of viral gastroenteritis (causes up to 90% of outbreaks of epidemic viral gastroenteritis)
-Self-limiting after a couple of days
-Transmission Contact Precautions: Enteric Contact Precautions
Hepatitis E (Liver Inflammation)
-Self-limiting
-Low Mortality Rate (2%)
-Risk of becoming chronic
-Transmission Contact Precautions: Enteric Contact Precautions
Sapovirus (Most common cause of acute gastroenteritis or the "stomach flu/stomach bug")
-"Star of David" appearing virion
-Causes vomiting, diarrhea, and sometimes chills, nausea, muscle aches, headache, stomach ache, and occasionally a fever
-Transmission Contact Precautions: Enteric Contact Precautions
-Known as the winter vomiting virus
-Named after Norwalk, OH
-Transmission Contact Precautions: Enteric Contact Precautions
Norovirus (Gastroenteritis and watery diarrhea, Nausea, Projectile Vomiting, Abdominal Pain, Loss of Appetite and Taste, Lethargy, Weakness, Muscle Pain, Headache, Low-Grade Fever)
-Also known as the winter vomiting virus
-The most common cause of viral gastroenteritis (causes up to 90% of outbreaks of epidemic viral gastroenteritis)
-Self-limiting after a couple of days
-Transmission Contact Precautions: Enteric Contact Precautions
Hepatitis E (Liver Inflammation)
-Self-limiting
-Low Mortality Rate (2%)
-Risk of becoming chronic
-Transmission Contact Precautions: Enteric Contact Precautions
Sapovirus (Most common cause of acute gastroenteritis or the "stomach flu/stomach bug")
-"Star of David" appearing virion
-Causes vomiting, diarrhea, and sometimes chills, nausea, muscle aches, headache, stomach ache, and occasionally a fever
-Transmission Contact Precautions: Enteric Contact Precautions
noroviruses (norwalk viruses):
hepatitis e:
sapovirus:
Astroviruses
Astroviruses (Diarrhea, Gastroenteritis, Nausea, Vomiting, Fever, Malaise, Abdominal Pain lasting 3-4 days in children and adults)
Astrovirus is a nonenveloped, positive-sense, single-stranded RNA virus. Named for the Greek term "astro", meaning "star,", this virion has a star-like appearance in the center. There are 8 known serotypes of this virus. Serotype 1 is the most common type, and is typically seen in young children as a mild virus causing watery diarrhea, stomach cramps, vomiting, fever, and loss of appetite lasting 1-4 days following an incubation period of 4-5 days. The interesting thing about this virus is that once symptoms have subsided, the virus particles can still be shed in the stool for up to 2 weeks!
Adults typically do not get this virus unless they are immunocompromised. It is most common amongst children and is milder than Rotavirus or Calcivirus. It is spread via the fecal-oral route through contaminated food or water. It replicates in the epithelial cells of the small intestine.
Astrovirus is a nonenveloped, positive-sense, single-stranded RNA virus. Named for the Greek term "astro", meaning "star,", this virion has a star-like appearance in the center. There are 8 known serotypes of this virus. Serotype 1 is the most common type, and is typically seen in young children as a mild virus causing watery diarrhea, stomach cramps, vomiting, fever, and loss of appetite lasting 1-4 days following an incubation period of 4-5 days. The interesting thing about this virus is that once symptoms have subsided, the virus particles can still be shed in the stool for up to 2 weeks!
Adults typically do not get this virus unless they are immunocompromised. It is most common amongst children and is milder than Rotavirus or Calcivirus. It is spread via the fecal-oral route through contaminated food or water. It replicates in the epithelial cells of the small intestine.
coronaviruses (other than sars-covid-19):
Coronaviruses (Common Cold/Upper Respiratory Tract Infection)
reoviruses:
Rotavirus (Diarrhea in infants, toddlers, young children)
CO Tick Fever (Mountain Tick Fever; American Tick Fever)
-Caused by the bite of the Rocky Mountain Wood Tick (Dermacentor andersoni)
-Infects hematopoetic erythrocytes
-Highest infections occur during the summer in June
-The virus may stay in the body for up to 4 months after initial infection
-Incubation is up to 20 days but symptoms begin to appear about 3-6 days after the bite
-Fever, chills, headaches, pain behind the eyes, myalgias, photophobia, malaise, abdominal pain, hepatosplenomegaly, nausea, vomiting, rash; May require hospitalization
-Complications may include meningitis, encephalitis, hemorrhagic fever
CO Tick Fever (Mountain Tick Fever; American Tick Fever)
-Caused by the bite of the Rocky Mountain Wood Tick (Dermacentor andersoni)
-Infects hematopoetic erythrocytes
-Highest infections occur during the summer in June
-The virus may stay in the body for up to 4 months after initial infection
-Incubation is up to 20 days but symptoms begin to appear about 3-6 days after the bite
-Fever, chills, headaches, pain behind the eyes, myalgias, photophobia, malaise, abdominal pain, hepatosplenomegaly, nausea, vomiting, rash; May require hospitalization
-Complications may include meningitis, encephalitis, hemorrhagic fever
Rotavirus:
Rotavirus tends to infect infants, toddlers and young children, but adults can also become infected. There is a vaccination for babies given at 2, 4 and 6 months or at 2 and 4 months of age, depending upon the vaccination type. Both of these vaccinations are oral vaccinations.
In the clinical setting, rotavirus requires enteric contact transmission precautions to prevent the spread of the virus to other patients and healthcare workers. It is spread via the fecal-oral route, by ingesting contaminated virus particles, which can be by contaminated food or water, or coming into contact with contaminated surfaces or objects. The virus is more prominent during the winter and spring months, but can occur year round. A PCR test can detect the virus very quickly.
This virus is characterized by vomiting and diarrhea for 3-8 days, which may quickly result in dehydration, dizziness, and a higher fall risk. Fever and stomach pain may also be present. Loss of appetite, decreased urination, dry mouth, dry skin, irritability, and drowsiness are also common symptoms. The incubation period of the virus is typically 2 days.
Treatment is nonspecific, but focuses on oral rehydration and/or IV fluid therapy to treat or prevent dehydration.
In the clinical setting, rotavirus requires enteric contact transmission precautions to prevent the spread of the virus to other patients and healthcare workers. It is spread via the fecal-oral route, by ingesting contaminated virus particles, which can be by contaminated food or water, or coming into contact with contaminated surfaces or objects. The virus is more prominent during the winter and spring months, but can occur year round. A PCR test can detect the virus very quickly.
This virus is characterized by vomiting and diarrhea for 3-8 days, which may quickly result in dehydration, dizziness, and a higher fall risk. Fever and stomach pain may also be present. Loss of appetite, decreased urination, dry mouth, dry skin, irritability, and drowsiness are also common symptoms. The incubation period of the virus is typically 2 days.
Treatment is nonspecific, but focuses on oral rehydration and/or IV fluid therapy to treat or prevent dehydration.
rocky mountain spotted tick fever:
picornaviruses:
Enteroviruses (Common Colds, Hand-Foot-Mouth Disease, Conjunctivitis, Aseptic Meningitis, Myocarditis, Acute Flaccid Paralysis)
Polio Virus
Coxsackie A Virus (Hand-Foot-Mouth Disease): see attached file below under Coxsackie A Virus Hand-Foot-And-Mouth-Disease
-May cause birth defects in infected infants
-Herpangina (mild, self-limiting illness that consists of a fever, sore throat, small red vesicles on the back of the throat)
Coxsackie B Virus (Mild Gastroenteritis, Myocarditis, Pericarditis)
-Fever, headache, sore throat, GI distress, chest pain, muscle pain
-Complications include myocarditis, pericarditis, aseptic meningitis, pleurodynia
-Most common cause of unexpected sudden death
-Possible cause of Diabetes mellitus type 1
Echovirus
-Highly infectious and infects children
-Causes aseptic meningitis
Enterovirus 68-71
Enterovirus 72 (Hepatitis A)
Rhinovirus (The Common Cold, PNA in the Immunocompromised)
Polio Virus
Coxsackie A Virus (Hand-Foot-Mouth Disease): see attached file below under Coxsackie A Virus Hand-Foot-And-Mouth-Disease
-May cause birth defects in infected infants
-Herpangina (mild, self-limiting illness that consists of a fever, sore throat, small red vesicles on the back of the throat)
Coxsackie B Virus (Mild Gastroenteritis, Myocarditis, Pericarditis)
-Fever, headache, sore throat, GI distress, chest pain, muscle pain
-Complications include myocarditis, pericarditis, aseptic meningitis, pleurodynia
-Most common cause of unexpected sudden death
-Possible cause of Diabetes mellitus type 1
Echovirus
-Highly infectious and infects children
-Causes aseptic meningitis
Enterovirus 68-71
Enterovirus 72 (Hepatitis A)
Rhinovirus (The Common Cold, PNA in the Immunocompromised)
Polio virus:
hand-foot-and-mouth-disease: Coxsackieviruses (a16, a6, enterovirus):
coxsackievirus_infection_facts.docx | |
File Size: | 346 kb |
File Type: | docx |
rhinovirus:
Human rhinoviruses are one of the most common causes of the common cold. These viruses typically are mild and self-limiting, however, in the hospital-based setting, they can sometimes cause complications, including pneumonia. Individuals with weakened immune systems are more susceptible, and those with asthma or other underlying conditions or disorders are more apt to experience complications from the normally simple virus. Early Autumn and early Spring are the times of the year where we see more cases of the virus, but it can occur year-round. Adenoviruses, RSV, and Influenza Virus A and B can also cause similar symptoms.
Transmission isolation precautions for those hospitalized with this virus include droplet AND contact precautions. This virus spreads via respiratory droplets that spray when a person sneezes or coughs. They can be breathed in, but they can also spread when contaminated surfaces are touched, then the individual touches their mouth, nose, or eyes. Direct contact can also spread the virus, when shaking hands with someone or hugging them.
Many people who become infected with a rhinovirus remain asymptomatic, however, they can still spread the virus. Symptoms tend to include:
There is no vaccination for this virus, and no specific treatment other than treating the symptoms. It is important to stay hydrated to avoid dehydration. The virus typically lasts about 7 days.
Transmission isolation precautions for those hospitalized with this virus include droplet AND contact precautions. This virus spreads via respiratory droplets that spray when a person sneezes or coughs. They can be breathed in, but they can also spread when contaminated surfaces are touched, then the individual touches their mouth, nose, or eyes. Direct contact can also spread the virus, when shaking hands with someone or hugging them.
Many people who become infected with a rhinovirus remain asymptomatic, however, they can still spread the virus. Symptoms tend to include:
- Fever
- Body aches
- Chills
- Fatigue
- Sore throat
- Achy muscles and joints
- Cough
- Sneeze
- Runny Nose
- Nasal congestion
There is no vaccination for this virus, and no specific treatment other than treating the symptoms. It is important to stay hydrated to avoid dehydration. The virus typically lasts about 7 days.
Arenaviruses:
Lymphocytic Choriomeningitis
Lassa Fever
Hemorrhagic Fevers
Lassa Fever
Hemorrhagic Fevers
rhabdovirus:
Rabies
filoviruses:
Ebola Virus
Marburg Virus
Marburg Virus
retroviruses:
Human T-Cell Lymphotrophic Virus (HTLV-1, 2)
HIV/AIDS
HIV/AIDS
phages and bacteriophages:
culturing viruses:
viral cell Culture media:
Immunofluorescence microscopy:
Immunofluorescent staining of various instracellular structures of the hela cell culture line using multiple fluorescent tags:
Green fluorescent protein/fluorescein:
Green fluorescent protein or fluorescein is found naturally in the jellyfish Aequorea victoria.