Micro 12/07/12 RNA Respiratory Viruses – Flashcards
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| What picornavirus causes the common cold and upper respiratory infections? |
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| Rhinovirus |
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| Is there a vaccine for rhinovirus? |
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| No--there are over 100 serotypes and infection is self-limited |
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| What does rhinovirus bind to? |
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| ICAM-1 |
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| What is the surface structure of rhinovirus? |
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| The surface has a common pocket antigen and a variable knob antigen |
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| Why is rhinovirus seasonal? |
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| Its optimal temperature is 33*C |
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| How is rhinovirus spread? |
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| By direct contact from hands and fomites or by inhalation of droplets |
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| What viruses are in the orthomyxovirus family? |
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| Influenzas A, B, and C |
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| What is each influenza important in? |
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| Influenza A is important in pandemics, influenza B is important in local epidemics, influenza C is not very common |
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| What forms the influenza envelope? |
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| Neuraminidase and hemagglutinin, which forms clusters of cells |
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| How is the influenza genome set up and what is special about it? |
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| The -RNA is helical and has 8 segments, and it carries its own RNA polymerase. Unlike other RNA viruses, it enters the nucleus to steal a cap for the RNA |
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| What is antigenic drift? |
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| Simple mutation of NA or HA sites, but antibodies can still recognize the virus |
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| What is antigenic shift? |
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| Simultaneous infection of different orthomyxoviruses results in reassortment, leading to a new antigen |
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| How many HA subtypes are there? NA? |
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| 15 HA and 9 NA |
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| How do highly infective, pandemic flu strains arise? |
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| Segmental recombination of a successful avian (swine, etc.) influenza that underwent drift with a human influenza is reassortment that leads to viruses infective to multiple species |
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| What causes the flu symptoms? |
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| The body's response of IFN induction, cell-mediated immunity, and desquamation of mucous secreting respiratory cells |
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| What is Reye's syndrome? |
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| A neurological complication of influenza, characterized by acute encephalopathy along with fatty degeneration of the liver. Mortality is up to 40% |
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| What is Guillian-Barre syndrome? |
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| An autoimmune reaction to the flu leading to muscle weakness or self-resolving paralysis secondary to viral affliction of the peripheral nervous system |
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| How do antivirals affect influenza? |
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| Amantadine and zanamivir inhibit replication or block neruaminidase |
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| What is the best control for influenza? |
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| Annual vaccines |
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| What is the immune response to a second influenza exposure? |
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| If the virus is a variant (as it likely is), the individual will only make antibody to previously experienced epitopes, not to the new epitopes |
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| Why do antibiotics not affect the flu? |
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| They would only work on pneumonia caused by a secondary bacterial infection, which is extremely rare |
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| What do coronaviruses look like? |
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| They are medium-sized enveloped virions that look like crowns under a microscope |
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| How is the genome of coronavirus set up? |
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| It is +RNA and is translated in phases, assembled at the RER |
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| How do coronaviruses present? |
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| Typically as the common cold, but can also cause GI disease |
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| What are the rare complications of coronavirus? |
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| Viral pneumonia, myocarditis, and SARS |
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| Where does coronavirus cause infection? |
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| It infects the epithelium of the upper respiratory tract, where it is restricted because it survives best at 33-35*C |
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| What protection does the coronavirus have? |
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| The envelope allows it the possibility of surviving the GI tract, and it is not destroyed by serum antibodies |
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| What is the structure of paramyxoviruses? |
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| Helical nucleocapsid with -RNA and HA/NA envelope |
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| What are the primary diseases of parainfluenza? |
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| Croup, pneumonia, and bronchitis |
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| Who is at highest risk for parainfluenza 1/2 and what time of year? |
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| Children under 5; autumn |
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| What are the symptoms of parainfluenza based on? |
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| Symptoms are based on where in the URT the virus replicates (larynx through lungs) Laryngitis: croup, hoarseness, barking cough Bronchiolotis: cough, dyspnea, etc. |
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| How many serotypes does parainfluenza have? |
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| 4 |
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| How many serotypes are there for mumps? |
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| 1 |
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| What does mumps cause? |
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| Severe parotitis and rarely, meningitis |
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| How is mumps transmitted? |
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| Via respiratory droplets only in humans. It has an 18 day incubation period |
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| How does mumps virus replicate? |
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| In the URT before disseminating to other sites, mainly the parotid glands, which become enlarged |
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| What are possible sequelae of mumps? |
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| Orchitis, pancreatitis, and meningoencephalitis |
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| What comprises the envelope of measles virus? |
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| HA, but not NA |
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| What is the pathology of measles? |
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| Rash and rarely encephalitis |
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| How is measles transmitted? |
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| It is highly infectious and affects the respiratory tract in humans only. Incubation is usually 9 days, and symptoms last about a week |
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| How does measles virus spread in the body? |
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| It spreads from the URT through blood and lymph to endothelial cells and T-cells |
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| What are key symptoms of measles? |
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| Maculopapular rash, high fever, conjunctivitis, coryza, and cough followed by lifelong immunity. The rash starts discrete but becomes confluent and spreads rapidly. Koplik's spots are present |
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| What are Koplik's spots? |
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| Clustered, white ulcerative lesions on the buccal mucosa |
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| What is subacute sclerosing panencephalitis? |
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| Caused by CNS infection with defective measles virus. It is characterized by behavioral changes, myoclonic jerks, and blindness. |
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| What are complications of subacute sclerosing panencephalitis? |
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| If cell-mediated immunity is defective, viral replication can continue and cause death |
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| What is respiratory syncytial virus? |
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| A pneumovirus that does not disseminate from the URT. The virion is large but not resistant to desiccation and is spread by large-droplet aerosols |
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| What is the cause of the symptoms in RSV? |
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| Pneumonia is due to viral cytopathic effects; bronchiolitis is mediated by host immunity |
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| What happens to children or adults who contract RSV? |
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| Infants are hospitalized with fever, cough, dyspnea, and cyanosis. Young kids get febrile rhinitis. Adults just get cold symptoms |
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| How is RSV resolved? |
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| Humanized IgA or antiviral ribavirin must be given because maternal IgG cannot protect infants, natural infection does not confer immunity, and there is no vaccine |
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| What is the single most important cause of severe respiratory illness in small children? |
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| Respiratory syncytial virus |
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| What family contains rubella virus? |
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| Togavirus |
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| What is the structure of rubella virus? |
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| Enveloped +RNA virion |
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| What is the action of rubella virus? |
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| It disseminates from the pharynx, causing fever, rash, and long-lasting lymphadenopathy |
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| How does the rash caused by rubella present? |
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| It is a red, maculopapular rash that spreads from the upper body to the lower body |
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| How does rubella affect a fetus? |
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| Rubella virus spread through the blood and across the placenta can be stopped by antibodies. Congenital infection can lead to cataracts, heart defects, deafness, intrauterine growth retardation, or microcephaly. In general, growth retardation results in failure to thrive and death within a year |
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| What is the MMR vaccine? |
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| Measles, mumps, and rubella vaccine contains live, attenuated viruses of single serotypes. Vaccination at 15 mo, 4-6 years, and before junior high. 95% develop lifelong immunity with a single dose |
