029 Viral Infections on Respiration

Question 1

What are aerosols?

Answer 1

Light particles that are airborne, which can cause transmission of virus.

Question 2

What are fomites?

Answer 2

Inanimate objects that can harbor pathogens e.g. door handles.

Question 3

What is the most important respiratory pathogen of childhood, causing annual winter epidemics and hospital outbreaks?

Answer 3

RSV is most important, causing the common cold (rhinitis).

Question 4

What are the characteristics of RSV?

Answer 4

It is a paramyxorvirus and envelopes RNA. It is very close to the human metaphneumovirus. It has a syncytial cytopathic effect, so under light micrograph of virus infected cells in culture, you will see several cells fused together.

Question 5

What are common diseases for the upper respiratory tract and their virus causes?

Answer 5

Rhinitis (common cold) – caused by RSV, adenovirus, corona viruses, pharyngitis (sore throat) – caused by influenza, parainfluenza, adenoviruses, Laryngotracheobronchitis (croup) – RSV, influenza, human metapneumovirus.

Question 6

What are common diseases for the lower respiratory tract and their virus causes?

Answer 6

Bronchiolitis, Bronchitis, Pneumonia – RSV, influenza, parainfluenza

Question 7

What is malaise?

Answer 7

Malaise refers to general feeling of illness.

Question 8

What is myalgia?

Answer 8

Myalgia refers to muscle pain.

Question 9

What type of genetic material do influenza envelope and how many segments is it split into?

Answer 9

Influenza envelope SS viral –ve sense RNA and it is split into 8 segments.

Question 10

What is the incubation period for influenza?

Answer 10

1-3 days

Question 11

What is the period of infectivity of influenza?

Answer 11

3-5 days after illness onset

Question 12

Describe some complications for influenza?

Answer 12

Primary viral pneumonia, Secondary bacterial pneumonia, Reyes syndrome. Reyes syndrome is the inflammation and swelling of liver and brain in children, usually caused by the intake of aspirin. It is quite rare, but is associated with fits, oedema, coma, and altered mental state.

Question 13

What is the difference between primary viral pneumonia and secondary bacteria pneumonia?

Answer 13

Primary viral pneumonia occurs by the influenza virus penetrating the alveoli. It is very rare and is associated with rapid deterioration and death due to cyanosis etc. Secondary bacteria pneumonia is caused by the disruption in mucosal immunity caused by the influenza, allowing opportunistic bacterial infections to occur. This is normally caused by streptococcus pneumonia or Staphylococcus aureus.

Question 14

On histology slides, what do the small purple dots represent?

Answer 14

Neutrophils – you will extensive neutrophils in secondary bacterial pneumonia but less in primary viral pneumonia.

Question 15

What is the difference between latency and incubation?

Answer 15

Latency is the time period between infection and communicability. Incubation is time period between infection and onset of symptoms.

Question 16

How is the influenza classified, and which is the result of antigenic shifts?

Answer 16

Influenza is classified into flu A, B, C. Flu A is the most severe and is the result of antigenic shifts. Flu B presents with more mild symptoms. Flu C is not present in man.

Question 17

What is the difference between antigenic shift and antigenic drift?

Answer 17

Antigenic drift is caused by single point mutations that are not corrected by RNA polymerase. There are lots of slow changes accumulated over time, and eventually the virus changes enough to cause an epidemic as humans will be partially immune. Antigenic shift is where reassortment occurs as the coinfection of two viruses will swap from their 8 sections, causing 256 variations. This forms an entirely new virus. Genetic reassortment can also occur. This normally causes epidemics and pandemics.

Question 18

What are the two antigens and the variations on the influenze?

Answer 18

Haemagglutinin – there is H1 – H3 on humans for flu A but H1-H15 for all species. Neuraminidase – there is N1, N2 in humans for flu B but N1-N9 for other species. Flu B only has one HA and NA subtype.

Question 19

What is the role of haemagglutinin?

Answer 19

HA attaches to sialic acid on cells, causing fusion and endocytosis to the influenza envelope.

Question 20

What is the role of neuraminidase?

Answer 20

NA cleaves the sialic acid off from the HA, allowing the newly formed virus to be released from the cell surface.

Question 21

What is the M2 (Matrix -2) protein ion channel and what is it specific to?

Answer 21

M2 protein ion channel is found in flu A strains. When HA binds to sialic acid on the cell surface in an acid environment, protons enter virus via the M2 protein ion transport channel allowing uncoating of viral nucleic acid.

Question 22

How would you write a vaccination classification?

Answer 22

Virus type / place of origin / strain number / year of isolation (subtype)

Question 23

How would you clinically diagnose the influenza?

Answer 23

The quickest way would be to use the nasopharyngeal aspirates and immunofluorescence tests of epithelial cells to detect antigens. Host antibody response can be tested, by taking serum samples from patient 10-14 days apart to see if it has response to the antibody. Reverse PCR can be used to determine the nucleic acid for identification and possible isolation. For vaccination, isolation for strains can occur.

Question 24

Why does RSV reinfection often occur in children?

Answer 24

They have poor mucosal immunity

Question 25

What is the incubation period of RSV, and how long do symptoms last?

Answer 25

1-4 days but symptoms can last to up to 2 weeks later.

Question 26

Which receptor on the influenza is the main target for neutralization?

Answer 26

Haemagglutinin

Question 27

What is the use of amantadine? Which flu can this treat?

Answer 27

Amantadine is used to block M2 channels, to prevent the acid environment allowing protons to uncoated the viral RNA when inside the cell. It can be used to treat flu A.

Question 28

What do neuraminidase inhibitors do?

Answer 28

Inhibit neuraminidase from cleaving the HA off the saliac acid.

Question 29

Which treatment is mainly used and for what purpose?

Answer 29

Neuraminidase is normally used to reduce side effects because viruses develop resistance much more slowly. It can be used against both flu A and flue B. Amantadine also has CNS side effects.

Question 30

Which strain of flu broke out in Hong Kong 1997? How did the city respond to this?

Answer 30

H5N1, city responded by slaying 1.5 million chickens. There were 18 cases in humans.

Question 31

Why is H5N1 able to cause multi-organ disease?

Answer 31

An enzyme is needed to cleave the haemagglutinin before it is able to attach to other host cells. This enzyme is normally found only in the respiratory tract, causing localization. H5N1 haemagglutinin can be cleaved elsewhere and can be activated by enzymes in cells throughout the body, causing multi-organ disease.

Question 32

When did H1N1 break out and what was the epidemiology of this?

Answer 32

2005, mostly young people developed this because there was a similar outbreak in the 1918’s and 1977s, which made older people immune.