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IMED2001 > Acute Infections > Flashcards

Acute Infections Flashcards

1
Q

What are the patterns of infection by viruses?

A

Acute

Persistent smoldering (virus stays at same level all the time)

Persistent latent (viral infection effects come and go)

Persistent slow infections stay in the system for an extended time and then arise again to cause harsh symptoms again

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2
Q

What kind of diseases do acute infections cause?

A

Rapid, severe and self limiting

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3
Q

When do acute infections occur?

A

When intrinsic and innate immune responses are transiently bypassed

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4
Q

What are the stages of a typical acute infection?

A

Entry of virus -> Innate defenses -> Establishment of infection -> Induction of adaptive response -> Adaptive response -> clearing of virus

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5
Q

When is adaptive response triggered?

A

When a threshold level of virus is breached

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6
Q

What important immunological response arises while the virus is being cleared?

A

Memory cells begin to form

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7
Q

What is the period between infection and before symptoms arise called?

A

Incubation period

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8
Q

What happens during incubation period?

A

Viral genomes are being replicated and the host is responding producing cytokines (eg interferon)

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9
Q

From a clinical perspective what are the stages of viral infection?

A

Incubation period (no signs/symptoms) -> Prodormal period (minor signs/symptoms) -> period of incline (Most severe signs and symptoms) -> Period of decline -> Period of convalescence

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10
Q

Why are viral infections always associated with common public health problems?

A

Viruses have incubation period in which viruses could potentially evade detection by lab tests.

Treatment is often initiated late.

By the time the host is sick enough to stay home away from susceptible potential new hosts, transmission has already occured.

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11
Q

What is the types of virus associated with influenze?

A

orthoxomyoxoverdia

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12
Q

Which influenza virus undergoes the most genetic shift?

A

Influenza A

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13
Q

What does minus sense ssRNA mean?

A

Negatively polar single stranded RNA

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14
Q

What 3 genera of viruses infect humans?

A

Influenza A, B, and C

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15
Q

What are the 2 main proteins that make up influenza virus?

A

Hemagglutinin and neuraminidase protein

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16
Q

Which cells does the influenza virus attach to?

A

Respiratory tract cells

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17
Q

What are the terms used to describe the type of influenza causing disease?

A

Seasonal influenza (Most people have some immunity and there is a vaccine for seasonal flu)

Avian influenza (bird flu)

Swine influenza (swine flu)

Pandemic influenza (virulent human influenza that causes a global outbreak)

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18
Q

What subtype of avian flu is a current concern?

A

H7N9

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19
Q

What influenza subtype is associated with swine flu?

A

IV-A

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20
Q

Does swine flu cause infection in swine exclusively?

A

No, sporadically there are outbreaks seen in humans (from variant viruses) but this is not normal

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21
Q

What causes sporadic infections from swine to humans?

A

People exposed to a pig with a human variant form of the influenza

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22
Q

What is the incubation period of flu?

A

2 - 3 days

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23
Q

What are the clinical features of influenza?

A

Febrile illness (38 - 40 degrees) with shivering, malaise, headache, aching in limbs and back.

Not characterized by runny nose or sore throat

Severity is generally proportional to age and short-lived in young people. (babies are at risk of complicated influenza. Older people can take 3 - 6 months to recover from the flu.

IVA and B are similar

Secondary bacterial infection with strep pneumoniae may be life threatening

Reye’s syndrome in children can cause damage to liver that is often fatal

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24
Q

What syndrome causes encephalopathy with fatty degeneration of liver and other organs?

A

Reye’s syndrome which is a rare condition. (can also be seen in people recovering from chicken pox)

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25
Q

How does influenza cause disease?

A

Infection occurs in upper respiratory tract and virus replicates in nose and sinus passages resulting in IFN production as well as other cytokines which account for severe malaise.

26
Q

What happens when influenza viruses invade lower respiratory tract?

A

They can cause influenzal pneumonia which results in overwhelming toxaemia with high mortality due to virus replicating in alveolar epithelial cells.

27
Q

What are Influenza Viruses associated with regarding the cardiovascular system?

A

An increased chance of stroke and heart disease

28
Q

What are some drugs used to treat influenza A?

A

Amantadine and rimantadine which do not work on IVB and C.

29
Q

How do amantidine and rimantidine work?

A

They target IV ion channel protein M2.

This channel is required for viral RNA to be released into the host cell .

By blocking this channel low pH can not be inducted and therefore infection cant occur,

Amantidine requires patient to be given the drug within 36 hours of onset

30
Q

What does the IV ion channel do?

A

Allows passage of H+ ions to the interior of the virus which causes dissociation of viral RNP releasing viral RNA to enter nucleus to replicate.

31
Q

What does oseltamivir and zanamivir do?

A

Target neuraminidase which acts at stage of virus release from cell.

Compound prevents the virus from budding at cell surface and so virus particles begin to agreggate at cell surface instead of being released to infect adjacent cells.

32
Q

Which infections are oseltamivir and zanamivir effective agaisnt?

A

IVA and IVB

33
Q

Which drugs are more widely used N inhibitors or M2 blockers?

A

N inhibitors

34
Q

How are vaccines made for influenza?

A

Virus is grown in eggs or mammalian cells, purified and concentrated.

Viral lipid is dissolved by detergent releasing proteins and nucleic acid which is removed.

HA and NA subunits are purified by ultracentrifugation

Standardized quantities of HA and NA are incorporated into final product

35
Q

What is the risk of using CSL fluvax?

A

in children under 5 years it is dangerous and could cause increase in fever and convulsions

36
Q

What is the name of the virus that causes measles?

A

Paramyxovridae

37
Q

How dangerous is measles?

A

In developed countries measles causes mild infection and serious complications are rare.

Measles is a significant killer of children in developing countries

38
Q

How is measles transmitted and how contagious is it?

A

It is an airborne spread in viremic respiratory secretions and is one of the most contagious human viruses

39
Q

How is measles transmitted and how contagious is it?

A

It is an airborne spread in viremic respiratory secretions and is one of the most contagious human viruses

40
Q

When is measles most contagious?

A

2 - 3 days before rash

41
Q

Who develops symptoms in measles?

A

Almost all infected individuals.

42
Q

Where does measles stay persistent?

A

In the CNS (here is where it becomes lethal)

43
Q

What kind of nucleic acid does measles virus have?

A

(-) ssRNA

44
Q

How does measles cause disease?

A

It fuses with the plasma membrane of epithelial cells in respiratory tract and then spreads to lymphocytes and by viremia.

It replicates in conjunctivae, respiratory tract, urinary tract, lymphatic system, blood vessels, and CNS.

45
Q

What causes the rash seen in measles?

A

T cell response to infected cells of the endothelial cells causes a rash.

46
Q

What is requires to control measles infection?

A

CMI (Cell-Mediated Immunity)

47
Q

What kind of infection is measles? (self-limiting or persistent)

A

A self-limiting disease but can become persistent in rare cases.

48
Q

What happens in primary viremia?

A

Infected tissue displays giant cells and virus shedding occurs.

49
Q

What happens in secondary viremia?

A

Virus spreads to all body surfaces resulting in epithelial necrosis

50
Q

What are the characteristics of uncomplicated measles?

A

Uncomplicated measles is a self limiting disease.

Fever >38 degrees C

The 3 Cs: coryza, cough, and conjunctivitis

Koplik’s spots (tiny white spots with blue-white centers found inside mouth)

Rash (3 - 5 days after onset of symptoms)

51
Q

What are the characteristics of complicated measles?

A

1: 10 children get ear infection
1: 20 get pneumonia

Fatal for 1 - 2/1000

Subacute sclerosing panencephalitis (occurs years after infection) this results from infection in very young children (<2 years old) who seem to completely recover.

52
Q

What cells are targetted in subacute sclerosing panencephalitis?

A

Neural and gliac cells in the brain

53
Q

How long after primary infection does subacute sclerosing panencephalitis typically occur?

A

Average of 6 years after

54
Q

What are the early symptoms of subacute sclerosing panencephalitis? What can it lead to?

A

Starts off with confusion and lack of attentiveness and is followed by seizures and then 1 to 3 years after can cause death

55
Q

Why is immunosuppression associated with complicated measles?

A

During acute infection there is a strong Th1 cell mediated response. Infection resolves in the periphery but lies dorman in CNS briefly and then causes subsequent secondary infections due to the lymphopenia that resulted.

Another possible contributing factor is the switch from Th1 to Th2 cellular responses.

***Th1 (IFN-Y) and Th2 (IL-4 and 5) are subsets of the CD4 T cell group that produce different cytokines

56
Q

How does measles enter the CNS?

A

It is transported from one neuron to another by creating microfusions in the cell membranes of adjacent neurons by expressing viral F proteins which fuse with neurokinin-1 and bring cell membranes together. This creates openings for the viruses to travel through. Viruses at the cell membrane do not completely assemble and so they do not bud out which allows them to avoid antibody detection and promotes latency in the brain.

57
Q

Pathogenesis of measles:

A

Virus binds to respiratory epithelial cells where it starts to disseminate into the lymph nodes and then the blood affecting primary circulation where it goes to multiple organs causing rash, and other rare complications (encephalitis and subacute sclerosing panencephalitis).

Virus then enters epithelial cells again from the basolateral surface (binds to nectin-4) and replicates within the epithelial cells and is further released.

58
Q

Why are new outbreaks occuring with measles in modern times despite the vaccine?

A

Andrew Wakefield paper which gained a lot of media attention has caused people to not vaccinate and when measles is introduced from countries where vaccination rates are low the measles spreads rapidly in the developed countries

59
Q

Is measles a notifiable disease?

A

Yes

60
Q

What is investigated following notification of a measles case?

A

Review of vaccination status

Confirmation of onset date and symptoms

Clinical evidence should be compatible with case definition

Review of case contents

Contact tracing and follow-up of potential new cases - case finding; may involve media

Confirm lab tests or initiate them

Cases advised to stay in isolation

Vaccination is completed as necessary

61
Q

How common is measles in Australia?

A

Measles is no longer endemic in Australia however transmission is often associated with introduction from countries where transmission is maintained

IMED2001 (44 decks)

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