Virology 7 Respiratory Infections

Question 1

1. Identify the peak seasonal disease incidence (midwinter; Spring/Fall; no particular seasonality) due to the RSV, influenza viruses, rhinoviruses, parainfluenza viruses, coronaviruses, and adenoviruses (figure 2).

Answer 1

influenza viruses, coronaviruses and respiratory syncytial virus peaks in the winter months

rhinoviruses, parainfluenza viruses: peaks in fall and spring

adenoviruses: throughout the year, periodic outbreaks in institutional settings

OTHERS: metapneumovirus, human bocavirus and WU virus

**enterovirus peaks in late summer and early fall; NOTE seaonsality is not a useful diagnostic tool

Question 2

2. Identify the most common age group acquiring serious disease due to RSV, describe the common clinical manifestations in this patient group.

Answer 2

RSV causes serious LRT in infants between 6mo and 1 yr, boys are hospitalized more frequently than girls

Question 3

2. Discuss the epidemiologic predispositions (low socioeconomic status; pediatric; nosocomial;newborn nursery and daycare; sometimes elderly), factors favoring transmission, and the approaches to controlling nosocomial outbreaks.

Answer 3

.

Question 4

3. Describe and explain the lower respiratory manifestation (bronchiolitis) caused by RSV and discuss how it is diagnosed and treated.

Answer 4

LRT symptoms are often preceded by what looks like common cold

Question 5

4. Discuss clinical manifestations, pathogenesis, and seasonal distribution of the influenza virus.

Answer 5

clinical manifestation: fever, malaise, muscle aches and cough (esp. extreme fatigue and muscle aches)

Question 6

4. Discuss antigenic shift and drift, antiviral therapy, and preventive measures of the influenza virus.

Answer 6

generation of a virus with a new H protein is known as antigenic shift, the acquisiton of point mutation in the H and/or N proteins that increase the resistance of the virus to the host gimme response is termed antigenic drift,
antigenic drift and shift lead to changes in the composition of the vaccine each year

novel H subtypes exist in nature that have never before been seen by humans and their introduction creates a virus no one has seen before

influenza irons contain two envelop glycoproteins (hemagglutinin) and neuraminidase, the former is critical for attachment and entry into the cell while the later is important for efficient viral release; there are immune responses generated for each H and N subtype

Question 7

5. Identify the respiratory syndrome attributable to parainfluenza viruses.

Answer 7

typically causes cold sometimes with bronchitis, 50-75% of illness is associated with fever over 100F for 2-3 days

more serious manifestations include croup (type 1 and 3) or pneumonia and bornchiolitis (type 3), boys are more frequently hospitalized with type 1 and 2 infections, re-infection is common

Question 8

6. Identify the major groups of “common cold” viruses and describe how they are
   transmitted from person to person.

Answer 8

rhinoviruses
coronaviruses
adenoviruses
RSV
parainfluenza
human metapneumovirus
enteroviruses

common cold: runny nose, congestion, coughing, sore throat, and usual lack of fever; symptoms are caused by replication of viruses in the epithelial lining of the URT

Question 9

7. Describe the importance of rhinoviruses in infectious asthma.

Answer 9

viruses trigger the synthesis and release of chemotactic factors for eosinophils and increased numbers of these cells in the epithelium can lead to exacerbation of asthma or COPD

Question 10

7. Explain why a vaccine against the rhinoviral common colds has proven to be so elusive.

Answer 10

there are many serogroups for rhinovirus

Question 11

8. Explain the epidemiological risk factors of transmission (fomite/skin contact > aerosol dissemination) of the common cold due to rhinovirus.

Answer 11

peak titers of virus are shed by people in the day or two prior to the appearance of symptoms for most viruses

aerosol transmission can occur but more so, viral survival on surfaces contaminated by wet secretions – therefor frequent hand washing is the most effective defense, humidity affects survival, sneezing into a sleeve and using disposable tissues

also, avoid contact between your hands and mucosal surfaces such as conjunctiva, nose and mouth (reduce transmission)

Question 12

List the symptoms of the common cold and their common (general) pathogenesis.

Answer 12

common cold: runny nose, congestion, coughing, sore throat, and usual lack of fever; symptoms are caused by replication of viruses in the epithelial lining of the URT and the release of histamines and bradykinins

can kill epithelial cells, but not always and cilia action is commonly paralyzed

Question 13

What damage is common with SARS CoV?

Answer 13

diffuse alveolar damage, desquamation, hyaline membranes, alveolar edema, inflammation, syncytial formation and thickened alveolar walls

Question 14

What are common OTC medications for treating the symptoms of respiratory infection?

Answer 14

purchase drugs that relieve a specific symptom instead of combination formulations
influenza does little with decongestions
common cold, fever reducers not usually present
aspirin should not be given to children to prevent Reye’s syndrome and acetaminophen recommendations need to be followed to prevent liver damage

zinc inhibits one of the rhinoviruses proteases, echinaceas to increase immune response has not been proven with clinical trial, the same can be said for Vit. C

Question 15

Discuss antivirals that are available to treat influenza.

Answer 15

amantadine and rimatadine (resistance mostly in the US)

susceptability for two neuraminidase inhibitors oseltamivir and zanamivir- these prevent the release of the virus from the cell and must be started within 48hrs of onset of symptoms and can be use prophylactically in settings such as nursing homes

Question 16

What is ribavirin and what are its indications? What are other recommendations to prevent RSV?

Answer 16

aerosolized ribavirn is currently approved for use in infants hospitalized with respiratory syncytial virus (some debate about efficacy)

palivizumab (monoclonal antibody directed against RSV fusion protein) is used to prevent infection in high risk children and for therapy in severe cases

breastfeeding is can confer anti-RSV antibodies secreted by the mother

Question 17

What characteristic of pandemic strains make them so virulent?

Answer 17

viruses that cause pandemics encode a new subtype of H that people have never seen before and are thus not protected

genetic reassortment has been found to be the key factor int eh ability of the virus to cause pandemics (produced when two viruses enter the same cell and are segments are randomly packaged)

Question 18

Describe a mixing vessel that can result in the reassortment of influenza viruses.

Answer 18

the pig can be infected with human and avian types of influenza virus, presenting the ideal situation for the generation of reasserted viruses

Question 19

What types/strains of flu are most commonly seen in humans?

Answer 19

type A and type B strains

Question 20

What is the clinical presentation of influenza?

Answer 20

abrupt onset with incubation period of 1-2days
fever up to 104F, headache, myalgia, fatigue that can be extreme, dry cough, sore throat and nasal congestion (caused by cytokine release from infected respiratory tract)

systemic systems last 3-5 days, respiratory signs 3-4 days longer and the cough can persist for some time after viral clearance, full lung recovery can take weeks

(runny nose is not common, GI symptoms are also not prominent although patients may report vomiting due to the fever

Question 21

Describe the ways in which influenza can lead to pneumonia in more serious cases

Answer 21

influenza can cause viral pneumonia which rapidly progresses to dyspnea and marked hypoxia (no lobar consolidation) most commonly in children, elderly and pregnant women

flu infection can be followed by development of secondary bacterial pneumonia signalled by production of sputum with productive cough and lobar consolidation usually in elderly or those with pulmonary disease (S. pneumo, S, aureus or H. influenzae)

Question 22

5. Identify the respiratory syndromes attributable to adenoviruses.

Answer 22

viruses cause latent infections and the site of latency appears to be in the adenoids and tonsils

infant predominant signs are cough and pharyngitis, children pharyngitis and tracheitis, more severe respiratory disease in teens and young adults with cough, low grade fever, sore throat and runny nose, in adults looks like a cold

immunocompromised can develop pneumonia, with dissemination (cystitis and CNS infection) can cause epidemic karatoconjunctivitis and a few serotypes can cause hemorrhagic cystitis, particularly in children, also GI specific serotypes

Question 23

5. Identify the respiratory syndromes attributable to coronaviruses.

Answer 23

15% of all colds, peak in winter and spring, re-infeciton is common, diarrhea may alos be present

symptoms include headache, sore throat, cough, malaise and sometimes low grade fever, runny nose is less common and pneumonia is very rare, can exacerbate respiratory problems

sub group of severe acute respiratory syndrome associated with corona virus SARS-CoV- jumped from civet cats or bats into humans: pregresses to fever over 100F, rigors, dry cough, dyspnea, malaise, headache and hypoxia, 27% with diarrhea and respiratory support is commonly needed

Question 24

5. Identify the respiratory syndromes attributable to respiratory syncytial virus.

Answer 24

symptoms begin with nasal congestion, pharyngitis, fever (not as high as flu) followed by the development of dyspnea and wheezing

symptoms can be referred to as bronchiolitis, febrile pneumonitis or bronchitis, croup is rare, re-infection is common due to poor development of immunity is poor, RSV can also cause otitis media and sinusitis and can lead to secondary bacterial otitis media, sinusitis, and pneumonia

CXR shoes interstitial infiltrates and hyperinflation
boys are hospitalized more than girls

Question 25

5. Identify the respiratory syndromes attributable to rhinovirus.

Answer 25

most common respiratory viral pathogen encountered, infections are seasonal most common clinical presentation is headache, sneezing, runny nose, sore throat, and congestion (little or no fever, usually without severe myalgia and fatigue) remains predominantly in the URT, although can exacerbate asthma, also associated with acute otitis media, sinusitis and predisposing to bacterial OM and sinusitis) cold or smoking does not predispose to infection, smoking does predispose to more severe illness (day care and schools are a major source of transmission)

Question 26

5. Identify the respiratory syndromes attributable to enteroviruses.

Answer 26

peak incidence in late summer or early fall, "summer gripe", symptoms similar to colds, sore through, cough and fever common, LRT rare, complications with acute myocarditis (exacerbated by exercise)