Respiratory Viruses

Question 1

Are upper or lower respiratory tract infections more severe?

Answer 1

Lower, e.g. bronchiolitis or pneumonia, might result in hospitalizations

Acute respiratory tract infections mostly involve upper airways but can also involve lower respiratory tract

Question 2

Why do we monitor influenza and vaccinate yearly?

Answer 2

Influenza has antigenic shift and drift, with genetic reshuffling where hemagglutinin and neuraminidase can exist in different combinations

Therefore we need to conduct influenza surveillance to detect the different viruses in the community to predict required vaccinations

Question 3

Laboratory diagnosis method for respiratory viruses?

Answer 3

Multiplex PCR assays which can detect multiple different respiratory viruses

Immunofluorescence for antigen

Virus isolation and antibody detection serology for public health surveillance

Question 4

Common symptoms for respiratory viruses

Answer 4

Often cause upper respiratory tract infection like sore throat, runny nose, laryngitis, middle ear infection

May cause pneumonia, esp with influenza, adenoviruses and SARS-CoV-2
Viral pneumonia can lead to secondary bacterial infection by Strep pneumoniae or staph aureus

Question 5

What are orthomyxoviruses?

Answer 5

Influenza!

Influenza A or B depends on M protein

Influenza A has haemagglutinin and neuraminidase determining the subtypes (H3N1, H1N1 etc)

-ve strand RNA in 8 segments, enveloped with surface proteins H and N

Question 6

What is antigenic shift?

Answer 6

New virus due to reassortment among the 8 gene segments esp in animal “mixing vessels”, may lead to pandemic

Question 7

What is antigenic drift?

Answer 7

Change in antigenicity from season to season due to accumulation of RNA mutations

Question 8

Symptoms of influenza?

Answer 8

Headache
Runny/stuffy nose
Sore throat
Aches
Fever
Muscle tiredness
Coughing
Vomiting

Question 9

Pathogenesis of influenza

Answer 9

Direct viral cytopathic effects followed by immunopathologic effects
May cause secondary bacterial infection, primary viral pneumonia, with CNS and muscle involvement

Fever and muscle aches when mounting immune response

Question 9

Pathogenesis of influenza

Answer 9

Direct viral cytopathic effects followed by immunopathologic effects
May cause secondary bacterial infection, primary viral pneumonia, with CNS and muscle involvement

Fever and muscle aches when mounting immune response

Question 10

How are respiratory viruses transmitted?

Answer 10

Mostly through large droplets and fomites (contact)

Question 11

How to treat influenza?

Answer 11

Neuraminidase inhibitors like oseltamivir

Question 12

How to prevent influenza infection?

Answer 12

Immunization via mostly inactivated vaccine derived from egg cultures

Trivalent: 2 influenza A subtypes + 1 influenza B lineage

Quadrivalent: 2 A subtyles + 2 B lineages

Newer types of vaccines include aerosolized/cell culture-derived attenuated live vaccines with low severity and virility

Question 13

What are paramyxoviruses?

Answer 13

-ve ss RNA, enveloped, 2 surface glycoproteins mediating cell entry (F and HN/H/G)

Includes measles, mumps, RSV, metapneumovirus, nipah virus etc

Question 14

How does measles spread?

Answer 14

Highly contagious, respiratory droplets –> airborne spread

Question 15

Symptoms of measles infection?

Answer 15

Cough, conjunctivitis, coryza, photophobia, respiratory tract symptoms, viremia and virus presence in respiratory tract and urine, koplik spots preceding measles rash

Rarely causes giant cell pneumonia, high mortality rate, affecting children with immunodeficiency

Question 16

How to diagnose measles infection?

Answer 16

Measles antigen via immunofluorescence
PCR
IgM, IgG detection

Question 17

How to prevent measles infection?

Answer 17

Immunization via measles-mumps-rubella MMR vaccine, consisting of a live attenuated virus

Question 18

What are the symptoms of mumps?

Answer 18

Recovery of virus from mouth or urine, orchitis, parotitis, CSF presence, meningoencephalitis

Question 19

How to diagnose mumps?

Answer 19

Mumps antigen by immunofluorescence
PCR
IgM, IgG detection

Question 20

Features of coronaviruses?

Answer 20

+ve ss RNA, enveloped, with surface proteins (M and S)

Animal reservoirs

Causes pneumonia

Question 21

SARS-CoV-2 pathogenesis?

Answer 21

2-14 day incubation period, mean of 3 days

S protein binds to ACE2 receptor to enter human lung, heart, kidney and intestinal cells

Virus undergoes rapid replication within target cells, inducing epithelial and endothelial dysfunction causing inflammatory response with cytokine and chemokine production

Pro-inflammatory cytokines and chemokines cause neutrophil activation, migration and cytokine storm, can lead to adverse effects

Question 22

Symptoms of SARS-CoV-2 infection?

Answer 22

Fever, cough, GI symptoms, can be asymptomatic

Multisystem inflammatory syndrome is where activation of inflammatory response, often involving the respiratory tract, can lead to acute respiratory damage, distress, and static shock, especially in children

Deterioration of taste (dysgeusia) and loss of smell (anosmia)

Non-dehydrating diarrhoea, vomiting, abdominal pain

Acute kidney infarction more prevalent among those with baseline renal impairment

Headache, confusion, delirium, altered mental status, ataxia, seizures

Thrombocytopenia, prolonged clotting times, increased ALT, bilirubin, serum urea, creatinine, lowered albumin

Question 23

How is SARS-CoV-2 transmitted?

Answer 23

Direct contact or respiratory droplets, or aerosols

Also can spread via oral-faecal route and fomites

Question 24

How to treat SARS-CoV-2 infection?

Answer 24

Dexamethasone or remdesivir