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The RNA Viruses

The RNA Viruses. Chapter 25. Electron microscope. Influenza. Orthomyxoviruses INFLUENZA. enveloped, segmented ssRNA viruses Influenza A (circulates in many species) Influenza B (circulates widely only in man) Antigenic Drift (minor change caused by mutations)

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The RNA Viruses

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  1. The RNA Viruses Chapter 25 Electron microscope

  2. Influenza

  3. Orthomyxoviruses INFLUENZA enveloped, segmented ssRNA viruses • Influenza A (circulates in many species) • Influenza B (circulates widely only in man) • Antigenic Drift (minor change caused by mutations) • Antigenic Shift (major alteration occurring when segments recombine)

  4. Shift and Drift Yearly variations in the “Seasonal Flu” are the result of antigenic drift.

  5. 2009 H1N1…”swine flu”

  6. 2009 H1N1…”swine flu”

  7. Influenza type A • acute, highly contagious respiratory illness • seasonal, pandemics • among top 10 causes of death in US • respiratory transmission • binds to ciliated cells of respiratory mucosa • causes rapid shedding of cells, stripping the respiratory epithelium, severe inflammation • fever, headache, myalgia, pharyngeal pain, shortness of breath, coughing • treatment: amantadine, rimantadine, zanamivir & oseltamivir • annual vaccine

  8. Vaccination for “seasonal flu” • There are two types of vaccines: • The "flu shot"— an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. • The nasal-spray flu vaccine— a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “live attenuated influenza vaccine” or FluMist®). LAIV (FluMist®) is approved for use in healthy* people 2-49 years of age who are not pregnant. • Each vaccine contains three influenza viruses-one A (H3N2) virus, one A (H1N1) virus, and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists' estimations about which types and strains of viruses will circulate in a given year. • About 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body. • Seasonal flu peaks in the U.S. in Jan and Feb

  9. Orthomyxoviruses INFLUENZA Is an Avian Flu pandemic on the way??

  10. Avian Flu Why would “Bird Flu” be a big deal? Pandemic viruses appear as the result of antigenic shift, which causes new combinations of proteins on the surface of the virus. If the new virus spreads easily from person to person a pandemic can result.

  11. Avian Flu

  12. Avian Flu

  13. Avian Flu • Culling of infected Poultry

  14. Is a Pandemic coming???? Nations with confirmed cases of H5N1 avian flu

  15. NOVA Science NOWPandemic flu video (2006) http://www.pbs.org/wgbh/nova/sciencenow/3302/04.html

  16. Paramyxoviruses • enveloped ssRNA • Paramyxoviruses (parainfluenza, mumps virus) • Morbillivirus (measles virus) • Pnuemonovirus (respiratory syncytia virus) • respiratory transmission • virus causes infected cells to fuse with neighboring cells – syncytium or multinucleate giant cells form

  17. Fusion of cells allows passage of virus directly between cells Giant Cell

  18. Parainfluenza • as widespread as influenza but more benign • respiratory transmission • seen mostly in children • minor cold, bronchitis, bronchopneumonia • Most common cause of croup • Barky cough with hoarse voice and some respiratory difficulty • Croup symptoms may be cause by many respiratory viruses • no specific treatment available

  19. Mumps • epidemic parotitis • self-limited, associated with painful swelling of parotid salivary glands • humans are the only reservoir • 40% of infections are subclinical • Now only about 300 cases in US/year • incubation 2-3 weeks fever, muscle pain & malaise, classic swelling of both cheeks • complications: in 20-30% of infected young adult males, epididymis & testes become infected; sterilization is rare • live attenuated vaccine MMR

  20. Parotitis- inflammation and swelling of parotid salivary glands

  21. How Iowa Got The Mumps How Iowa Got the Mumps • In 2006 Iowa got the mumps. Over 2000 individuals got mumps infection in the first half of 2006 (in a normal year there are on avergae 5 cases per year) • Probably originated … in the UK? 26

  22. Measles • caused by Morbillivirus • also known as red measles & rubeola • different from German measles • very contagious • transmitted by respiratory aerosols • humans are the only reservoir • less than 100 cases/yr in US • virus invades respiratory tract • sore throat, , dry cough, headache, conjunctivitis, lymphadenitis, fever, Koplik spots – oral lesions • rash

  23. Measles Rash Fully developed rash White lesions adjacent to molars

  24. Signs of measles

  25. measles • most serious complication is subacute sclerosing panencephalitis (SSPE), a progressive neurological degeneration of the cerebral cortex, white matter & brain stem • 1 case in a million infections • involves a defective virus spreading through the brain by cell fusion & destroys cells • leads to coma & death in months or years • attenuated viral vaccine MMR

  26. RSV respiratory syncytial virus • also called Pneumonvirus • infects upper respiratory tract & produces giant multinucleate cells • most prevalent cause of respiratory infection in children 6 months or younger; Very young are most susceptible to serious disease • epithelia of nose & eye portal of entry • replicates in nasopharynx • rhinitis, wheezing, otitis, croup • treatment: Synagis (a monoclonal antibody that blocks attachment), ribavirin

  27. Rabies Only 1 or 2 human cases per year Iowa 1951 then not again until 2002

  28. RhabdovirusesRABIES • bullet-shaped virions, enveloped • slow, progressive zoonotic disease • virus enters through bite, grows at trauma site for a week , enters nerve endings & advances toward the ganglia, spinal cord & brain • furious form of rabies – agitation, disorientation, seizures, twitching, hydrophobia • dumb form of rabies – paralyzed, stuporous • treatment – passive & active postexposure immunization

  29. Rabies

  30. RNA Viruses

  31. Coronavirus • relatively large RNA viruses with distinctively spaced spikes on their envelopes • common in domesticated animals • 3 types of human coronaviruses have been characterized • HCV causes a cold • an enteric virus • Severe Acute Respiratory Syndrome (SARS)

  32. CoronavirusesSARS (severe acute respiratory syndrome) 2003 Outbreak… 8,098 people worldwide became ill, 774 died. Spread to 30 countries before the outbreak was contained.

  33. SARS

  34. Coronavirus- SARS Global Spread… Feb 21,2003 …infected medical doctor from Guangdong Province spent a night at a Hong Kong hotel. 12 people staying at or visiting that floor of the hotel became infected. These travelers then dispersed the disease to other countries worldwide

  35. SARS Dispersal Superspreaders 144 of Singapore’s 206 cases linked to contact with just 5 individuals

  36. Palm civets (SARS reservoir??) Did the SARS epidemic start in Guangdong Province, China as a “civet meal”? Masked Palm Civet at market Water rat at a market

  37. Cost of SARS

  38. Rubella • caused by Rubivirus, a Togavirus • German measles • Was considered a fairly harmless childhood disease until teratogenic (congenital defects) effects discovered • transmitted through contact with respiratory secretions • attenuated viral vaccine MMR

  39. Rubella • postnatal rubella – malaise, fever, sore throat, lymphadenopathy, rash, generally mild • congenital rubella – infection during 1st trimester most likely to induce miscarriage or multiple defects such as cardiac abnormalities, ocular lesions, deafness, mental & physical retardation

  40. Arboviruses • viruses that spread by arthropod vectors – mosquitoes, ticks, flies, & gnats • More than 400 viruses spread this way • Viruses of many families: togaviruses, flaviviruses, some bunyaviruses & reoviruses • most illnesses caused by these viruses are mild fevers, but some cause severe encephalitis • Examples: dengue fever, western- & eastern equine encephalitis, yellow fever

  41. Arboviruses

  42. Togaviruses (Flavivirus subcategory) • Dengue • “breakbone fever” severe pain in muscles and joints. Infections usually mild, but dengue hemorrhagic shock can be lethal • Concern over possible spread to the continental U.S. • Yellow Fever • Fever, headache, muscle pain, may progress to organ failure and death. • Mosquito control has greatly decreased its impact • West Nile • Emerging concern in U.S.

  43. Dengue American countries with laboratory-confirmed hemorrhagic fever (red shaded areas), prior to 1981 and from 1981 to 1997. Distribution of Aedes aegypti (red shaded areas) in the Americas in 1970, at the end of the mosquito eradication program, and in 1997

  44. Aedesaegyptimosquito Figure 25.11

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