CSIM 1.71 Respiratory Viruses Flashcards by K W

Describe rhinovirus virology:

1) Envelope
2) Genetic material
3) Incubation period

Non-enveloped
- Positive sense ssRNA
- Incubation 2-3 days (cold)

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Why do rhinoviruses affect the nasal cavity?

Their optimum growth temperature is 33ºC, the temperature of the nasal cavity

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How is rhinovirus transmitted?

Respiratory

* Hand to mouth

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Describe adenovirus virology
• Envelope
• Genetic material

Non enveloped

* dsDNA

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How many adenovirus species are there?

Which causes gastroenteritis?

7 (A-G)

Adenovirus F

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Describe the external structure of an adenovirus

External hexon capsid with penton bases at each vertex, and a fibre protruding from each (IMG 175)

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What structure of the virus binds to human cells? What specifically does it bind to?

The fibres protruding from the penton bases bind to “Coxsackie B virus and adenovirus receptor” (CAR)

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What pathologies and symptoms can adenovirus cause?

Cold and fever
- Conjunctivitis
- Tonsillitis
- Bronchiolitis and pneumonia (atypical)
- Diarrhoea

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How can a cold caused by adenovirus and rhinovirus be differentiated?

Adenovirus colds will cause a fever, rhinovirus colds will not

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Describe the transmission of adenoviruses

Respiratory
- Hand to mouth
- Faecal/oral

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How can adenovirus be diagnosed (in severe cases)?

PCR
- Antigen tests
- Culture
- Serology (antibodies)

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Describe the virology of coronaviruses
• Envelope
• Genetic information

Coronaviruses
• Non-enveloped
• positive sense ssRNA

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How are coronaviruses diagnosed

RT-PCR (RT = reverse transcriptase, because the RNA needs to be made into DNA before PCR can occur)
- Serology
- Culture

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What pathologies does coronavirus cause?

SARS!!!!!

* MERS

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Describe the symptoms of SARS

Describe the transmission of SARS

10 to 20 days after exposure:
  •  High fever
  •  Cough
  •  Diarrhoea
20 to 30 days after exposure:
  •  Pneumonia

7 to 30 days after exposure:
  •  Nasopharynx virus secretion 
14 to 30 days after exposure:
  •  Faecal viral excretion
20 to 30 days after excretion:
  •  Viruria

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What are the symptoms of MERS?

Fever
- Cough
- Shortness of breath
- Death (30%)

Which virus is the most common causative agent of bronchiolitis? What family is it a part of? Describe the following virology:
• Envelope
• Genetic information

Respiratory syncytial virus (a paramyxovirus)
• Enveloped
• Negative sense ssRNA

What are the symptoms of a respiratory syncytial virus infection

Bronchiolitis:
• Cough
• Wheezing
• Sneezing

How is RSV diagnosed in severe cases?

RT-PCR
- Culture
- Antigen tests

What drug can be given to treat RSV in episodes of severe bronchiolitis?

Palivizumab - a monoclonal antibody.

Describe the main epidemiological characteristics of RSV

Peaks in winter
- Majority of infections under 1 year old
- Incidence rates are unstabe between years

What family of viruses is the influenza virus a member of?

Describe the virology of this family:
• Envelope
• Genetic information
• Number of chromosomes/RNA segments

Orthomyxoviruses
• Enveloped
• Negative sense ssRNA
• 8 RNA segments

Describe the transmission and incubation period of influenza virus

Respiratory transmission

* 2-3 days incubation

What are the symptoms of influenza virus?

Vomiting
- Muscular tiredness/aches
- Coughing
- Sore throat
- Running nose
- Headache
- Fever

When is influenza defined as an 'epidemic'?

When there are more than 200 recorded infections in a geographic area per 100,000 (do not confuse with pandemic which is worldwide)

What are the serotypes of influenza? 1) Which of these undergo antigenic shift and drift? 2) Which of these are the most severe? 3) Which animals have each? 4) What are the subtypes of each?

Influenza A, B and C 1) Only A undergoes antigenic shift, all undergo drift 2) A is the most severe (pandemics), followed by B (epidemics) then C (sporadic) 3) A: humans, pigs, birds, horses, marine mammals B: Humans C: Humans and pigs 4) A, subtypes are dependent on HA and NA (e.g. H1N1). B & C have no subtypes

From which day does the following occur (after infection)? 1) Virus in respiratory secretions 2) Interferon induction/cytokine storm 3) Clinical symptoms 4) Respiratory pathological changes 5) Rise in virus specific antibody

1) 1 day 2) 3 days 3) 4-5 days 4) 5-6 days 5) 6 days

Decribe the structure of influenza virus: 1) envelope 2) Protein core 3) Antigens

1) Matrix-protein, surrounded in a lipid bilayer Matrix bilayer links the viral core to the lipid bilayer 2) Nucleo-protein (NP) which links the genetic material together into a structure 3) Neuraminidase and (NA) haemagglutinin (HA) present (IMG 176)

What is the function of neuraminidase?

Antigen which aids viral release from infected cells

What is the function of haemagglutinin?

Antigen which binds to target cell surfaces (to allow entry)

How many types of HA and NA are there?

NA: N1 - N10 HA: H1 - H17

Recall the difference between antigenic drift and antigenic shift

DRIFT: • Accumulation of point mutations over time • Results in a new strain ever 4 years • Causes epidemics SHIFT: (INFLUENZA A ONLY) • Recombination/reassortment of coinfecting viruses • Creates a novel virus every 10-20 years • Causes pandemics IMG 177

What is the treatment for influenza?

Neuraminidase inhibitors (therefore prevents viral release) • Tamiflu • Relenza

Describe the vaccines for influenza

Inactivated vaccines containing purified HA and NA subunits