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?

1.The virus causes destruction of ciliated respiratory epithelium in the upper respiratory tract. This degrades the mucociliary elevator and prevents efficient clearance of bacteria. 2.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.

1.An similar pandemic occurred within their lifetime. 2.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

1.New human type A strain 2.Causing serious illness 3.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.A widespread rash B.An out of date national anthem. C.Last years skirt lengths

List the common exanthem viruses and families

IllnessGenusfamily MumpsParamyxovirusparamyxoviridae MeaslesMorbillivirusparamyxoviridae RubellaRubivirustogaviridae Roseola infantumHHV6, adenovirus, coxackie virus, echovirus Erethema InfectiosumParvovirus B19

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 morbillivirus spikes

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 Erythema Infectiosum?

Parvovirus B19

Where does the exanthema appear?

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

What is the alternative name for Erythema Infectiosum?

Fifth disease

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

Roseola infantum

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

Aedes aegypti

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 nile sx

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.

Reovirus arbovirus 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 (-)

Filovirus sx

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