Respiratory Viruses 1

Question 1

URTI causing viruses

Answer 1

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

Question 2

Common cold

Answer 2

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

Question 3

LRTI causing viruses

Answer 3

Parainfluenza virus, RSV, Influenza virus, Adenovirus

Question 4

Rhinovirus virus bio and infection

Answer 4

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

Question 5

Pathogenesis of Rhinovirus

Answer 5

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

Question 6

Inflammatory events with rhinovirus

Answer 6

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

Question 7

Transmission of rhinovirus

Answer 7

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

Question 8

Is stress a factor in getting a cold?

Answer 8

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

Question 9

Complications of rhinovirus infection

Answer 9

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)

Question 10

Immune reaction to rhinovirus

Answer 10

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

Question 11

Adenovirus

Answer 11

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

Question 12

Coronavirus

Answer 12

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.

Question 13

SARS

Answer 13

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

Question 14

RSV (Respiratory Syncytial Virus)

Answer 14

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

Question 15

Tropism and pathogenicity of RSV

Answer 15

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

Question 16

Symptoms of RSV

Answer 16

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

Question 17

Transmission and Tx of RSV

Answer 17

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

Question 18

Parainfluenza virus

Answer 18

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

Question 19

Diseases caused by parainfluenza

Answer 19

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.

Question 20

Parainfluenza virus pathogenesis

Answer 20

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

Question 21

Transmission of parainfluenza

Answer 21

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

Question 22

Complications of parainfluenza

Answer 22

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

Question 23

Influenza virus bio

Answer 23

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

Question 24

Influenza transmission

Answer 24

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

Question 25

Symptoms of Influenza

Answer 25

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

Question 26

Epidemics and pandemics of influenza

Answer 26

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.