Transcript By route of transmission-1 - Arkansas State University

By route of transmission-1
• Sexual contact
– HIV
– Human papilloma virus
– Hepatitis B and C
– Herpes simplex 2
• Other contact
– Epstein Bar
– Chickenpox
– MMR
Rhinovirus & other cold viruses
Influenza
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By route of transmission-2
• Vehicle
– Norwalk virus
– Hepatitis A
• Vector
– Rabies
– West Nile
– Aseptic meningitis, encephalitis
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Herpes family: Varicella Zoster
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• Varicella: chicken pox; Zoster: shingles
– Chickenpox (not a pox virus), respiratory, disease
becomes systemic with fever, malaise, skin lesions.
– Very contagious; usually mild, esp. in children
– Virus can become latent in nerves like Herpes
simplex
• Recurrence: shingles; rash, pain, on one side
• Acyclovir can lessen symptoms
– Beware of salicylates + viruses: Reyes syndrome
– Vaccination: Varivax: attenuated vaccine
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Shingles
Note how rash does not
cross the midline.
Shingles occurs most
frequently on the trunk,
but a Google search
shows pictures of face,
legs, etc. as well.
http://www.irishhealth.com/content/image/1191/shingles.jpg
Herpes family: Cytomegalovirus
• CMV (HHV5): Infection results in enlarged cells
– Widespread asymptomatic infections, latency
– Virus shed in body fluids: sex, birth, transplants
– Problem for unborn, immunosuppressed,
transplant patients; major cause of viralinduced birth defects.
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Epstein-Bar Virus
• Cause of infectious mononucleosis
• Infects B cells and salivary glands
– Spread by respiratory droplets, kissing
• Sore throat, swollen glands and spleen
• Long lasting fatigue
• Lympho-civil war: cytotoxic T cells attack
infected, altered B cells.
• Same virus causes B cell cancer (Burkitt’s
lymphoma) in Africa
– Some relationship to malaria exposure
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Picornaviruses
• Small RNA viruses (“pico” = very small)
– About 25 nm, near the size of a ribosome
– Two kinds
• Enteric viruses
– includes Hepatitis A and polio
• Only some cases of polio result in paralysis
– Cause of many cases of “stomach flu”
• Rhinoviruses: major cause of common cold
– Rhino means nose
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The Common cold
• Rhinoviruses have many serotypes
– Variants, caused by easy mutation of RNA
– Immune system can’t recognize all differences, but
some protection with age.
– Multiplies in narrow temperature range, nose/sinus
cooler than body temperature
• Other cold viruses
– Coronavirus (best known cousin causes SARS)
– Adenovirus (DNA virus), some serotypes cause GI
infections
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Orthomyxovirus
• Influenza: a serious respiratory disease
– Virus has a segmented genome
• 8 different RNA molecules
– Spikes: Hemagglutinin and Neuraminidase
• Major antigens recognized by immune system
• Antigenic drift and shift
– Drift: small mutations, making host susceptible
• Requires new vaccine each year
– Shift: major mixing of RNAs, whole new virus.
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View of flu
http://www.astrosurf.org/lombry/Bio/virus-influenza.jpg
http://www-micro.msb.le.ac.uk/3035/3035pics/flusection.jpg
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Nature of influenza
• Attack on respiratory tract
– Kills ciliated epithelial cells, allows bacterial
infections.
– Release of interferon from cells causes symptoms
• H antigen (hemagglutinin) for attachment
– That it agglutinates RBCs is an artifact
• N antigen: neuraminidase
– Cuts of the sugar on the glycoprotein receptor
– Allows new virions to escape from cell without
getting stuck
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Role of H and N spikes and host cell
polysaccharide
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influenza
• Changes in H and N (antigenic shift)
– Mixing of viruses that infect birds, pigs, produce
new strains able to jump to humans.
– New antigenic type leaves population unprotected
– Numerous epidemics throughout history
• Flu of 1918-1919 killed 20 million
– Asia watched very carefully: bird flu?
• Flu vaccines made from deactivated viruses
– Slow process (vaccine made in eggs), so every
year correct strains are “guessed”.
– Cell culture would be quicker but more $
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Paramyxoviruses
• Family of RNA viruses related to the influenza family
• Measles- Rubeola
– Childhood disease, still a global cause of illness
– Begins with respiratory infection, then fever and cold, then
systemic with characteristic rash
– Serious neurological complications in small percentage
– Series of MMR vaccine; killed vaccine was ineffective
• Mumps
– Infection in URT and nodes, then viremia
– Infection of glands, especially parotitis
• Orchitis, meningitis, deafness are complications
– Recent outbreaks in UK, Iowa. MMR vaccine
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Paramyxoviruses-2
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• Respiratory syncytial virus
– Respiratory disease of children, no vaccine
– Infants under 6 months may require hospitalization
•Rubella – German
Measles, a Togavirus
•was once the major viral
cause of birth defects.
•Mild, kills few cells.
•MMR vaccine important
Foodborne viruses
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• Norovirus (Norwalk)
– Restaurants, nursing homes, cruise ships
• Rotavirus- similar transmission
• Enteric Picornaviruses
– Hepatitis A virus
• Attacks GI especially liver
– Poliovirus – famous for paralysis, but only in a small
percentage; target for extinction.
• Spread by fecal-oral route
Arkansas Arboviruses
• Not an official taxonomic group, but short for
“arthropod-borne”
– Includes Flaviviruses, Togaviruses, and others.
– Zoonotic, spread from animals to people by
arthropod vectors, especially mosquitoes.
• Reservoirs may be birds, various mammals
– Result in two main types of illnesses
• Encephalitis, inflammation of the brain
• Hemorrhagic fever: high fever with bleeding
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Arkansas Arboviruses
• Encephalitis: spread by skeeters
– Eastern Equine encephalitis;
• Togavirus; summer 2005, outbreak in NE US
• Also infects, kills horses. Most dangerous.
– St. Louis encephalitis,
• Flaviviral diseases; Human disease.
• Usually not serious.
– West Nile virus
• Flavivirus; imported to US, spread from NYC
• Disease mostly in young and elderly
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Rabies
• Rhabdovirus- bullet shaped RNA virus
• Reservoir: animals of family Carnivora
– Foxes, bats, skunks, racoons, dogs and cats
• Virus elicits change in behavior of host
– Virus multiplies in salivary glands and brain
– Animals become agitated and bite, spread virus
– Humans show “hydrophobia”
• Long incubation, slow development
– Depends on dose, location.
– Vaccine AFTER inoculation
– # of survivors w/o treatment: 5
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