Respiratory Viruses 1 Flashcards Preview

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Flashcards in Respiratory Viruses 1 Deck (26):
1

URTI causing viruses

Rhinovirus*, Corona virus, Parainfluenza virus, Respiratory syncytial virus (RSV), Influenza virus, Adenovirus, Herpes simplex virus, Epstein-Barr virus

2

Common cold

Viruses involved: Rhinovirus and coronavirus (50% + 20%), Adenovirus, Parainfluenza and influenza, Coxsackie virus, RSV (respiratory syncytial virus)

3

LRTI causing viruses

Parainfluenza virus, RSV, Influenza virus, Adenovirus

4

Rhinovirus virus bio and infection

Picornavirus, ssRNA, + sense, non-enveloped. Similar to enterovirus, but inactive at pH <6.0. Infects only humans and primates. Usually resolves within 1 week. Typical symptoms: Sore throat, Sneezing, Runny nose, Sometimes low grade fever, Sometimes cough

5

Pathogenesis of Rhinovirus

Grows best at 33°C, involves URT (mucosal membranes are cooler)**. Most strains bind to ICAM-1 (intracellular adherence molecule-1) receptor on epithelial cells. Symptoms due to release of inflammatory mediators, e.g. histamine, kinins, prostaglandins, cytokines

6

Inflammatory events with rhinovirus

Dilation of blood vessels. Transudation of plasma. Secretion of seromucous glands and goblet cells. Stimulation of cough and sneezing reflexes. Swelling in nasal cavities. Mobilization of fluid into nasal cavities +/- sore throat, coughing and sneezing. Secretory IgA produced during infection may be important for resolution of the infection

7

Transmission of rhinovirus

most infectious during intense symptoms (2nd or 3rd day). Direct contact or droplet, hand hygiene important (Fomites important). Kissing is inefficient!

8

Is stress a factor in getting a cold?

Stress is not a factor in acquiring a cold, but may determine whether it becomes symptomatic

9

Complications of rhinovirus infection

Acute sinusitis (virus or virus followed by bacteria). Otitis media (up to 80% of young patients), often with bacteria. Exacerbations of chronic bronchitis. Precipitation of asthma (more in children >2 yrs)

10

Immune reaction to rhinovirus

Non-specific mechanisms of nose cannot contain the viral infection. Increased levels of kinins in nasal secretions, stimulate histamine release. ABs are produced to the specific rhinovirus, but these are not cross reactive to other rhinoviruses

11

Adenovirus

dsDNA, non-enveloped, many subtypes. Common in kids and military recruits. Can cause diarrhea, conjunctivitis, and epidemic keratinoconjunctivitis.

12

Coronavirus

ssRNA, enveloped. Common in animal infections, enteric strains exist. Human strains worldwide. Clinically indistinguishable from rhinovirus infection. Virus causes damage of cilia. Immunity short-lived. Transmission by respiratory droplets. No treatment, No vaccine. Can cause LRTI too.

13

SARS

A coronavirus but it was from an animal so new antigens etc.

14

RSV (Respiratory Syncytial Virus)

Paramyxoviridae, enveloped. Two types of virus, A and B. Found worldwide. Infects humans and several species of primates
Common in kids (most by 2 yrs). Severe in <8 mo of age. Can infect elderly and immunocompromised, disease resembles Influenza A in these patients

15

Tropism and pathogenicity of RSV

Target bronchioles. Wheezing and stridorous cough develops in infants with RSV (diameter of infant bronchioles is small and edema and necrosis caused by viral infection may lead to collapse and obstruction of airways). Can also result in involvement of lung parenchyma. Bronchiolitis common. Replication in respiratory epithelium. Causes ciliary dysfunction. syncytia causes degeneration of the respiratory epithelium

16

Symptoms of RSV

Mild to severe (bronchiolitis and pneumonia → death). First symptom in children is wheezing, apnea or periods of cyanosis/hypoxia. Fever in ~50%. LRTI is seen in ~30-40% of infected children, and pneumonia is more common in infants <6 months of age

17

Transmission and Tx of RSV

Contact method. Lab tests important for diagnosis.. No vaccine. Possible

18

Parainfluenza virus

Paramyxovirus, ssRNA, - sense, enveloped. Second most important cause of LRTI in small children. Antigenically stable. Types 1-3: infants and children. Type 4: adults. PIV 1: most common cause of croup (acute laryngotracheobronchitis). PIV 3: causes bronchiolitis and pneumonia

19

Diseases caused by parainfluenza

Croup: especially 6-18 mo old males. Fever, hoarseness, barking cough (seal-like) = Croup. Bronchiolitis: peak incidence in children <1 yr. Fever, Wheezing, Tachypnea, Rales, Pneumonia, Tracheobronchitis. Nonspecific URTI in adults.

20

Parainfluenza virus pathogenesis

Similar to RSV, Cytokines and immune modulators released, Tropism for respiratory epithelial cells, Use sialic acid on host cells as receptor (common)

21

Transmission of parainfluenza

Incubation: 5-6 days. Infectious dose low in infants. Shedding of virus 7 days. direct contact and large droplets

22

Complications of parainfluenza

interstitial pneumonia, giant cell pneumonia, otitis media, acute sinusitis, secondary bacterial infections (seen more often with PIV than RSV)

23

Influenza virus bio

Influenza A,B,C are enveloped orthomyxoviridae, segmented negative sense genome. Influenza A + B have 8 RNA segments, C has 7. Only Influenza A has subtypes

24

Influenza transmission

virus viable on hard surfaces 24-48 hours. Droplet transmission (airborne transmission unproven but suspected)

25

Symptoms of Influenza

Malaise, Fever, Headache, Myalgia, Cough, Sore throat. More severe in smokers

26

Epidemics and pandemics of influenza

Due to changes of Hemaglutannin and Neuraminadase antigens. Epidemics are annual and are a result of antigenic drift. Pandemics are a result of antigenic shift (2 viruses co-infect and combine), much more serious.