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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.

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Viral Disease

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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.

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.

Finally…

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?


Type A


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


Mumps

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.


RSV diagnosis


Immunofluorescence of nasal swabs


RSV prophylaxis


Injection of monoclonal antibody against factor F is indicated in high risk children


Its flu if?


It looks like a cold but also has

Myalgia/arthralgia

Fever


Adenovirus structure


Linear dsDNA


Adenovirus disease


URI particularly in children


Adenovirus persistence


DNA virus can establish latent/carrier state


What viruses are responsible for the common cold?


Rhinovirus

Coronavirus

Reovirus


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


Mumps complications


Orchitis

Meningitis

Encephalitis


Rubeola (Measles) time course


10 day incubation

5 days of rash

Koplik spots 1-2 days prior to exanthema


Rubeola epidemiology


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


Rubeola complications


Post infectious encephalitis in near term

SSPE (encephalitis) in 2-10 years


Rubeola sx


Progressive rash extending from head to toe.

High fever

Delirium

Photophobia

Conjunctivitis


Rubella time course


Incubation period 16 days

Exanthema for 3 days

Contagious -7 to +7 from rash


Rubella epidemiology


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


Cataracts

Cardiac defects

Reticuloendothelial defects (liver, spleen, thrombocytes)

Mental retardation


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?


Parvovirus B19


Where does the exanthema appear?


On the face. It has a characteristic slapped face appearance.


What is the alternative name for ErythemaInfectiosum?


Fifth disease


A child presents with a faint rash and convulsions. What is a likely diagnosis?


Roseolainfantum


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


Fecal-oral


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?


Polio

Echo

Rhino

Coxsackie

Hep A

(PERCH)


What are the three possible outcomes of polio infection


Abortive poliomyelitis

Aseptic meningitis

Paralytic poliomyelitis


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


Polio diagnostic


Viral visualization

Ab titer


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


70+


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)

Sexual contact

Public showers/swimming pools (suspected)

Perinatally


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?


20%-60%


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


Describe PML


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?


HIV


A bone marrow transplant patient presents a few weeks after discharge with hemorrhagic cystitis. What is the likely agent


BK polyomavirus


What is the tropic tissue for BK virus?


Kidney


What are the general sx of arbovirus


Encephalitis

Hemorrhagic fever


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?


Togavirus


What commonly togavirus is commonly vaccinated for?


Rubella


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


World wide.

Middle east, far east, Africa, Caribbean


What is the vector for yellow fever and dengue


Aedesaegypti


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


Birds


What is the vector for west nile?


Mosquitoes


West nilesx


Flu-like, Rash on torso and upper extremities


Describe the morphology of bunyavirus


ssRNA (-) , enveloped, spherical, segmented


California virus family and sx


Bunyavirus

Encephalitis with seizures

In north central mid west states


Hantavirus family


Bunyavirus


Hantavirus epidemiology


Direct exposure to rodent feces. Occurs in the southwestern US


Hantavirus sx and mortality


Fulminant respiratory disease with > 50% mortality.


Reovirusarbovirus disease


Colorado tick fever


Arenavirus morphology


Spherical enveloped ssRNA (+/-) segmented


Arenavirus unique characteristics


Ambisense (+/-) RNA

Presence of host cell ribosomes within virus


Filovirus morphology


Enveloped ssRNA (-)


Filovirussx


Hemorrhagic disease


Famous filovirus diseases


Marburg and ebola


What disease is cased by a rhabdovirus


Rabies


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


Prodrom

Acute neurologic phase

Coma

Death


What is the mortality of rabies


100%

(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


Rotavirus family


Reoviridae


Rotavirus structure


Small wheel shaped ssRNA (+). 1 segments


What are the segmented virus


Bunya

Orthomyxo

Arena

Reo

(BOAR)


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


Rotavirus prevention


Hand washing. Vaccine in development.


Rotavirus death factors and numbers


Malnutrition and immunodeficient children

600K die worldwide


Norwalkvirus family


Calcivirus


Calcivirus morphology


Naked small round ssRNA (+)


Norwalk disease


1-2 day incubation

1-2 day vomiting and diarrhea


Other diarrhea agents


Astrovirus (star shaped naked)

Adenovirus


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