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RESPIRATORY SYSTEM > Respiratory viruses and atypical respiratory pathogens > Flashcards

Respiratory viruses and atypical respiratory pathogens Flashcards

1
Q

As the respiratory tract is a continuum, what can be said about where viruses infect?

A

although many viruses can infect more than one part of the tract some are restricted to certain areas, due mainly to expression of different types of cell expressed receptors

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2
Q

What are the 2 main types of respiratory infection?

Which has the longest incubation period?

Give examples of both?

A

SURFACE - local spread of infection. e.g. common cold/candida

SYSTEMIC - spreads from mucosal site of entry to other site in the body. Then returns to surface for final shedding stage. e.g. measles, mumps, rubella

systemic has a longer incubation- weeks

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3
Q

What are the 2 types of invaders in a respiratory infection called?

A

professional invaders - can infect a healthy respiratory tract

secondary invaders - can infect a compromised tract

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4
Q

what is rhinitis and sinusitis commonly referred to as?

A

the common cold (an infection of the nasopharynx)

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5
Q

what are some features of the common cold?

transmission? cause? is it systemic?

A

caused by various viruses

transmission by aerosol

self-limiting virus and it isnt systemic in healthy people

identification is usually not necessary unless clinical symptoms worsen- Involvement of LRT.

•Molecular methods most common for ID, epidemiololgical info only

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6
Q

how does a viral infection (e.g. the common cold) actually infect us?

what causes the common cold symptoms?

A

Virus adheres to ciliated epithelium and avoids flushing out

Then it enters cells and replicates inside cells, this cell damage leads to release of the clear runny nose fluid.

And leads to activation of host defenses release of cell debris and transient damage to ciliated epithelium.

Then there is an immune response that might be accompanied by overgrowth of normal flora and finally recovery and regeneration of ciliated epithelium.

It is the inflammatory response which results in the classic cold symptoms

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7
Q

what are some common viruses that cause the common cold?

A

rhinovirus

adenovirus

echovirus

coxsackle virus A

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8
Q

what features does adenovirus have?

A

icosohedral symmetry

resistant to dessication

attaches via adhesins on the end of penton fibres

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9
Q

what % of pharyngitis and tonsilitis cases are caused by viruses?

what is the throat a site of entry for?

A

70%

Pharyngitis and tonsilitis are a common complication of common colds due to surrounding infections

Also the throat is a main site of entry of various viruses such as EBV (Herpes lecture) and Mumps virus (before dispersal around body)

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10
Q

MUMPS

what virus is mumps commonly caused by?

A

Paramyxovirus

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11
Q

MUMPS

how do they spread and who are most affected?

A

air-borne spread (via saliva, etc)

children most affected (school age)

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12
Q

MUMPS

what vaccine protects against it?

have there been bumps in the road with this vaccine?

A

MMR

MMR fear increased the occurrence in the UK for years

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13
Q

what is a complication of mumps?

A

orchitis - inflammation of the testicles

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14
Q

what are the common causes of laryngitis and tracheitis?

what are symptoms of these infections?

what particularly happens in children?

A

often caused by parainfluenza viruses, adenovirus and influenza

burning pain in the larynx and trachea

they can become obstructed, causing croup (causes a barking cough, hoarse voice and stridor)

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15
Q

BRONCHITIS AND BRONCHIOLITIS

what are the 4 viral causes?

what atypical pathogen can cause them?

what are 75% of bronchiolitis cases caused by?

A

rhinoviruses, coronaviruses (SARS), adenoviruses and influenza

atypically = mycoplasma pneumoniae

75% caused by respiratory syncytial virus

many cases are secondary infections (especially in children with narrower airways)

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16
Q

what are some features of RSV (respiratory syncytial virus)?

A

Aerosol and hand-hand/ surfaces transmission

Pathology creates large fused cells (Syncytia)

Outbreaks in winter months

Nearly all children have been infected by age 2- but often nothing more serious than common cold

Severe in young infants- peak mortality 3 months of age

symptoms in infants: Cough, cyanosis (blue lips), rapid respiratory rate: pneumonia and bronchiolitis

Older children and adults is more like a common cold.

Treatment supportive- hydration- bronchiodilators

Severe cases require ribavirin antiviral or Palivizumab-prophylactic in at risk groups (e.g. prem babies at risk (heart defect, lung disease, immunodef., in season)

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17
Q

what type of virus is orthomyxoviridae?

A

influenza virus

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18
Q

what are some features of Orthomyxoviridae virus?

A

Transmitted by aerosol droplet

Occurs worldwide- restricted to coldest months of year (people spend more time in warm conditions favouring droplet spread)

Initial infection: virus attaches to sialic acid receptors on epithelial cells via viral HA protein

1-3 days: liberated cytokines result in systemic chills, malaise, fever and muscle aches, runny nose and cough

Usually recover after 1 week, but some develop pneumonia and bronchitis and have lingering symptoms.

Secondary invaders can cause lethal infections: pneumococci, staphylococci

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19
Q

what is the major distinguishing feature of orthomyxoviridae compared to a common cold?

A

it has a more sudden onset of a fever and other symptoms

20
Q

what is the structure of influenza virus like?

A

two surface glycoproteins = HA (haemaglutinin) and NA (neuraminadase)

it has a host-derived viral envelope

it has a ssRNA genome of 8 segments - each one encoding a different part of the virus final particle

21
Q

How is HA (haemaglutinin) involved with the initial viral uptake? What are the stages from uptake to replication?

A
  • HA mediates binding to sialic acid containing receptors
  • internalised by endocytosis
  • Endosome acidified- HA conformation alters, M2 ion channel important here
  • HA mediates fusion of viral envelope and endosome membrane
  • Viral RNA and polymerases delivered into the cell
  • REPLICATION
22
Q

what are the major antigens of the influenza virus? (2)

what do each of them do?

A

HA = major antigenic determinant

HA binds sialic acid receptors on epithelial cell surface. It is a major source of antigenic variation.

NA = second antigen determinant

NA is involved in release of the virus from host cells during budding.

23
Q

what are the 3 types of influenza?

A

type A: Yearly epidemics and occasional serious worldwide epidemics- important animal reservoirs in birds and pigs

type B: cause of yearly epidemics- no animal reservoir

type C: minor respiratory illness- no epidemics. Less strong of an effect.

24
Q

how do we classify influenza using antigens?

A

H- antigen (HA):

  • 16 Avian and mammalian types
  • Only 3 are human adapted (H1-3)

N-antigen (NA):

  • 9 known serotypes
  • 2 human adapted (N1-2)
25
Q

what was H1N1 more commonly known as?

A

swine flu

26
Q

explain what antigenic drift is?

which types of influenza does it happen to?

A
  • Small point mutations in HA and NA that accumulate in population over time
  • Result in new variant viruses that can re-infect individuals
  • Source of yearly flu epidemics worldwide
  • mutations typically occur in antigenic parts of molecule =prevent antibody binding

Occurs in all types of influenza

27
Q

people with what allergy shouldn’t get a standard flu vaccine?

what does the vaccine contain?

when is it administered?

A

egg allergy - as the strains are grown in embryonated hen eggs

contains one H3N2 strain, one H1N1 strain and one B strain

administered yearly in october

28
Q

what is antigenic SHIFT?

which influenza does this only occur with?

A
  • Less common than antigenic drift
  • Results in major shift in viral composition – virus looks very different to what it used to
  • Major gene reassortment resulting in new HA and NA types
  • Little immunity in population
  • IT IS THE CAUSE OF MAJOR WORLD PANDEMICS
  • Only happens with influenza A
29
Q

HOW does antigenic shift happen and how does it lead to a worldwide pandemic?

A
  • There is the simultaneous infection of human/ animal with Human and ‘other’ influenza virus
  • Reassortment of genes due to homologous recombination with existing human virus
  • Circulation through immunologically naïve population
  • WORLDWIDE PANDEMIC
30
Q

Compare COVID-19 to the 1918 Spanish flu?

A

COVID deaths have low levels of death in younger people and high levels in elderly

1918 flu had more deaths in younger-middle aged people (20-30), not old people

31
Q

Compare SARS to COVID-19?

A

SARS was less infectious but more extreme symptoms and deadly – 10% death rate in SARS – originated from bats and civet cats. It fizzled out quite quickly.

32
Q

In the 1918 Spanish flu pandemic (HINI), how many people died?

Which age had an unusually high mortality rate?

A

Killed nearly 40 million people worldwide in a year. Extremely virulent and resulted in a 10-year drop in life.

Many deaths were from secondary infections (happened before antibiotics).

Unusually high mortality rate in young people.

33
Q

Will new strains of influenza arise?

A

Yes, they arise all the time

34
Q

What is GAP and its aims?

A

Global Action Plan

  • Increase in seasonal vaccine use
  • Increase in vaccine production capacity
  • Research and development
35
Q

Is bird flu next?

A

There are a lot of strains in birds that could recombine with present HINI and H3N2 strains to create a new pandemic

36
Q

How can we try an combat a pandemic using medicine?

give some e.gs of antiviral drugs that may be used?

A

VACCINES - these would require knowing which virus to create a vaccine against. Recombinant techniques should speed this process (difficult by the best option).

ANTIVIRAL DRUGS - resistance is a problem with these, and none of the drugs are that good. e.g. Tamiflu, Relenza, Peramivir.

37
Q

In influenza, what dominates in virulence and immunity?

A

HA and NA antigens

38
Q

What has been the source of several previous pandemics?

A

Avian influenza - bird (type A) influenza viruses. They can infect domestic poultry and other bird/animal species.

39
Q

What can cause pneumonia in children and in adults?

Do symptoms vary between organisms?

A

Often secondary to preceding damage (e.g. cystic fibrosis or influenza)

in adults, bacterial causes are more common (e.g. strep.pneumoniae formerly most common)

in children, mainly viral causes such as RSV or parainfluenza, or secondary to bacterial infections.

Neonates may acquire chlamydia from their mother in birth.

40
Q

TABLE: Showing the clinical conditions of each virus

A
41
Q

SARS-Cov-2 (COVID-19)

How many coronavirus types are there? Which are the 2 main ones?

Where did it originate?

Which receptor does the virus interact with and how?

A

7 coronavirus types infect humans (mainly SARS-Cov-I and MERS-CoV)

Originated from live wild animal markets.

The RNA virus genome has a spike on its protein surface which interacts with the receptor ACE-2 (angiotensin converting enzyme 2) which is present on airway cells, blood vessels, cardiac, CNS, etc…

42
Q

What is atypical pneumonia caused by?

what are the 3 main causes?

A

caused by BACTERIA, not viruses (typical pneumonia)

3 main bacterial causes:

Mycoplasma pneumoniae

Chlamydophila (formerly Chlamydia)

Legionella pneumophila

43
Q

What are some other terms for atypical pneumonia?

What are typical symtpoms?

A

Originally called pneumonia caused by penicillin resistant organisms.

Walking pneumonia - as patients with it are not hospitalised

Patients typically report chest pain, fever, cough, shortness of breath

44
Q

What can AIDS-associated pneumonia be caused by?

A

Pneumocystis spp (fungus)

Aspergillus spp (fungus)

45
Q

Which is more serious, atypical or classic pneumonia?

A

Classic pneumonia is more serious

46
Q

Can atypical pneumonia be treated in the same way as classic pneumonia?

A

NO - pneumonia that is NOT caused by S.pneumoniae is NOT treatable by penicillins.

But symptoms are generally less severe anyway.

RESPIRATORY SYSTEM (2 decks)

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