Viral Disease. Slackers Facts by Mike Ori. Disclaimer. The information represents my understanding only so errors and omissions are probably rampant. It has not been vetted or reviewed by faculty. The source is our class notes.
Slackers Facts by Mike Ori
The information represents my understanding only so errors and omissions are probably rampant. It has not been vetted or reviewed by faculty. The source is our class notes.
The document can mostly be used forward and backward. I tried to mark questionable stuff with (?).
If you want it to look pretty, steal some crayons and go to town.
If you’re a gunner, buck up and do your own work.
What are the three types in Orthomyxoviruses
A, B, C
Seasonal flu is what type?
Describe the genome of orthomyxovirus
Segmented ssRNA (-)
To what do H and N refer to
Hemagglutinin and neuraminidase spikes on the viral surface
In which portion of the cell orthomyxovirus replicate and why?
In the nucleus because they cannot prime their RNA strands
Why is the seasonal flu shot seasonal?
A new vaccine is required each year because of antigenic drift due to polymerase errors
Why does bacterial pneumonia often follow influenza?
The virus causes destruction of ciliated respiratory epithelium in the upper respiratory tract. This degrades the mucociliary elevator and prevents efficient clearance of bacteria.
General immune system down regulation occurs as the influenza infection is controlled.
What is the basis for the increased virulence seen in H1N1 of swine origin
Antigenic shift has substantially altered the virus to reduce its antigenic similarity to previous strains and to allow it to replicate in both the upper and lower respiratory tract.
Why are people over 50 less likely to get sick from H1N1 swine origin.
An similar pandemic occurred within their lifetime.
They do not have as robust an immune system and cannot generate as much of a cytokine storm
Why is avian flu H5N1 difficult to get
Currently the strain’s H antigen interact with sialic acid alpha 2,3 gal receptors which are situated in the lower respiratory tract. Thus it take larger exposures to transmit the disease.
What would occur if H5N1 reassorts in swine
Why are swine important intermediates in the assortment of avian and human influenza?
Swine upper respiratory epithelium contains sialic a2,3 gal and sialic a2,6 gal receptors thus they can be easily coninfected with both human and avian virus. This allows nature to tinker.
Idle goddesses are the devils workshop.
What will happen if H5N1 reassorts or mutates to efficiently infect both upper and lower respiratory epithelium.
The potential for significant mortality
What are the requirements of a pandemic influenza
New human type A strain
Causing serious illness
Easily spreads person to person
What diseases are caused by paramyxovirus
Parainfluenza and croup
Rubeola (5 day measles)
Respiratory syncitial virus
Describe the paramyxovirus spikes
Combined H and N on single spike (para=next to hence H is para to N)
Fusion (F) protein on second spike
What is a syncitia and why do they form
A syncitia is a giant cell that forms by fusion of multiple cells. Paramyxovirus tends to form syncitia through the action of F protein deposited on cell surfaces.
Distinguish parainfluenza from Respiratory syncitial virus
Parainfluenza = bronchitis
RSV = bronchiolitis
Describe RSV epidemiology
Occurs from the late fall to the spring. Predominantly affects small children < 1 yo.
Describe RSV immunity
Immunity is incomplete. Repeated infections occur with lessened severity but its unclear if there is an immune basis.
Immunofluorescence of nasal swabs
Injection of monoclonal antibody against factor F is indicated in high risk children
Its flu if?
It looks like a cold but also has
URI particularly in children
DNA virus can establish latent/carrier state
What viruses are responsible for the common cold?
What is a exanthema?
Circle the correct answer
Choose wisely grasshopper
A widespread rash
An out of date national anthem.
Last years skirt lengths
List the common exanthem viruses and families
What is the basis of the vaccine for these diseases
Combined attenuated vaccine for measles, mumps, and rubella. This avoids a rash of shots.
Mumps time course
16 day incubation
7 day clinical disease
Rubeola (Measles) time course
10 day incubation
5 days of rash
Koplik spots 1-2 days prior to exanthema
Occurs in unimmunized people typically in childhood or teens during the winter and spring.
What is unique about morbillivirusspikes
Even though they are paramyxoviridae they lack N activity. Thus they have H and F spikes as opposed to H/N and F typical of other paramyxoviridae.
What are koplik spots
Small bluish yellow spots that appear on the oral mucosa in advance of the rubeola rash
Post infectious encephalitis in near term
SSPE (encephalitis) in 2-10 years
Progressive rash extending from head to toe.
Rubella time course
Incubation period 16 days
Exanthema for 3 days
Contagious -7 to +7 from rash
Occurs in unimmunized people usually in the winter and spring
Should pregnant women receive MMR vaccine?
No, MMR is a live vaccine and rubella is a transplacental infective agent. Reversion of rubella to a virulent form could lead to congenital rubella in the child.
Congenital rubella sx
Reticuloendothelial defects (liver, spleen, thrombocytes)
What is the mechanism of spread for MMR?
All enter the respiratory tract to cause viremia before moving to their tropic tissue
What are the tropic tissues for MMR?
Mumps – salivary glands, testes, ovary, CNS?
Measles – skin and Lymph nodes?
Rubella – skin and lymph nodes?
What is agent for ErythemaInfectiosum?
Where does the exanthema appear?
On the face. It has a characteristic slapped face appearance.
What is the alternative name for ErythemaInfectiosum?
A child presents with a faint rash and convulsions. What is a likely diagnosis?
Describe the structure of Enteroviruses
They are small naked icosahedral virus with ssRNA (+) in picornaviridae
Pico = small
rna = RNA
What is the transmission path for enterovirus
Describe the stability of enterovirus
They are very stable and are resistant to acidic pH, detergents, disinfectants, and alcohol
Describe the epidemiology of enterovirus
Summer and fall in temperate climes. Year round in the tropics. Transmitted by direct or indirect fecal-oral contact. Vectors occasionally spread the virus.
What are the picornaviridae genus?
What are the three possible outcomes of polio infection
What is the entry point tissue for polio
Oropharynx. Resulting viruses swallowed and infect intestines. Then infect CNS
What vaccines are available for polio
Salk = killed
Sabin = Attenuated
What is the potential contagious period for polio
Intestinal shedding can occur for weeks even in the face of effective immune response
What is the structure of papillomavirus
dsDNA circular. Naked icosahedral
How many genotypes of HPV are known
What is the transformation potential of HPV
It’s a DNA virus and thus can be stabilized in the cell. Higher stain numbers are more oncogenic (?). Malignant strains seem to insert DNA into host genome.
HPV Transmission Routes
Occupational exposure (meat packers)
Public showers/swimming pools (suspected)
List the diseases associated with common HPV genotypes
1,2 – common warts
7 – meat handler warts
6,11 – benign genital warts
16,18,31,45 – warty lesions with malignant potential in the nethers
What percent of females in US are HPV positive?
Where does HPV replicate?
Nucleus – it’s a DNA virus
How is HPV typically diagnosed in females
Detected by cytoplasmic vacuolization and nuclear enlargement on routine pap smear
What is cryotherapy
Removing HPV infected epithelium with extremely cold substances such are liquid nitrogen
Degenerative brain disease that causes focal areas of demyelination surrounded by bizarre astrocytes.
What is the virus of PML?
The JC Polyomavirus
What is a likely comorbidity in PML PT?
A bone marrow transplant patient presents a few weeks after discharge with hemorrhagic cystitis. What is the likely agent
What is the tropic tissue for BK virus?
What are the general sx of arbovirus
What is the characteristic of an arbovirus?
They are all transmitted via insect vectors such as mosquitoes or ticks.
What is the family for arboviruses involving horses?
What commonly togavirus is commonly vaccinated for?
What is the distribution of western, eastern and St Loius encephalitis
Western – western us
Eastern – Eastern US
St Louis – central US?
Describe a typical WEE,EEE victim
People in association with horses where mosquitoes are present
What is the age range for St Loius and West Nile Virus
St Loius > 40
West Nile > 50
What is the classic distribution for yellow fever
Caribbean and south and central america
What is the classic distribution of Dengue
Middle east, far east, Africa, Caribbean
What is the vector for yellow fever and dengue
Describe Yellow Fever SX
Fever, chills, headache, hemorrhage, jaundice, and shock
Describe Dengue sx
Severe back and joint pain, fever, rash.
What is the reservoir for west nile
What is the vector for west nile?
Flu-like, Rash on torso and upper extremities
Describe the morphology of bunyavirus
ssRNA (-) , enveloped, spherical, segmented
California virus family and sx
Encephalitis with seizures
In north central mid west states
Direct exposure to rodent feces. Occurs in the southwestern US
Hantavirus sx and mortality
Fulminant respiratory disease with > 50% mortality.
Colorado tick fever
Spherical enveloped ssRNA (+/-) segmented
Arenavirus unique characteristics
Ambisense (+/-) RNA
Presence of host cell ribosomes within virus
Enveloped ssRNA (-)
Famous filovirus diseases
Marburg and ebola
What disease is cased by a rhabdovirus
Rabies virus morphology
Bullet shaped enveloped helical ssRNA (-)
What is the initial tx for rabies
Injection of IgG near bite. Vaccination with killed attenuated virus.
Describe the timecourse of rabies
Occurs from 10 days to one year depending on inoculum size
Classify the final stages of rabies infection
Acute neurologic phase
What is the mortality of rabies
(only a few exceptions are known)
What is the furious phase of rabies infection?
Occurs during the acute neurologic phase. Patients are often aggressive and disoriented
What is the dumb phase of rabies infection
Occurs during the acute neurologic phase. Patients are lethargic and paralytic.
Why isn’t everyone vaccinated against rabies
The vaccine is a killed attenuated vaccine so people receiving it are double protected form conversion but the protection does not last long so repeated vaccine would be necessary. Rabies is uncommon with proper precautions
Small wheel shaped ssRNA (+). 1 segments
What are the segmented virus
What is the epidemiology of rotavirus
Infection during cooler months in children < 2 years old. Highly contagious and spreads rapidly in institutions and families
Describe Rotavirus disease
1-3 day incubation period followed by abrupt onset of vomiting. Subsequent diarrhea lasting 5-8 days. Virus shedding for 2-12 days
Hand washing. Vaccine in development.
Rotavirus death factors and numbers
Malnutrition and immunodeficient children
600K die worldwide
Naked small round ssRNA (+)
1-2 day incubation
1-2 day vomiting and diarrhea
Other diarrhea agents
Astrovirus (star shaped naked)