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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 1 By route of transmission-2 • Vehicle – Norwalk virus – Hepatitis A • Vector – Rabies – West Nile – Aseptic meningitis, encephalitis 2 Herpes family: Varicella Zoster 3 • 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 4 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. 5 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 6 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 7 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 8 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. 9 View of flu http://www.astrosurf.org/lombry/Bio/virus-influenza.jpg http://www-micro.msb.le.ac.uk/3035/3035pics/flusection.jpg 10 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 11 Role of H and N spikes and host cell polysaccharide 12 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 $ 13 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 14 Paramyxoviruses-2 15 • 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 16 • 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 17 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 18 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 19