L20 Influenza

Question 1

Antigenic Types of Influenza?

Answer 1

Influenza A and B circulate globally and cause seasonal epidemics

Influenza A

Further classified into subtypes according to combinations of haemagglutinin (HA) & neuraminidase (NA) surface proteins

Influenza C:

detected less frequently

usually causes mild infections

does not present public health importance

Influenza D:

Primarily affect cattle

not known to infect or cause illness in people

Question 2

Influenza Genome?

Answer 2

Negative sense Single stranded RNA virus

Increases likelihood of genetic mutations

Question 3

____________ are the natural reservoir of all influenza A viruses

Answer 3

Wild aquatic birds are the natural reservoir of all influenza A viruses

Question 4

_________________: New influenza subtype (from the wild aquatic bird reservoir) into immunologically nave population

Mechanisms of Influenza A versus COVID Evolution?

Answer 4

Antigenic Shift: New influenza subtype (from the wild aquatic bird reservoir) into immunologically nave population

Antigenic variation occurs as a result of small changes over time within RNA segments encoding surface glycoproteins

Influenza A viruses evolve rapidly

RNA polymerase has no proofreading capability

Negative strand RNA: Each replication cycle involves two transcriptions => increased likleiehood of mutation

Virus at the end of influenza season will be slightly different than at the start

SARS COVID has proofreading exonuclease, evolves slower

Question 5

the single most fatal event in human history infecting ⅓ of human population => 50 million deaths?

Answer 5

1918/19 Spanish Flu (H1N1)

Avian virus that crossed to humans

the single most fatal event in human history infecting 1/3 of human population => 50 million deaths

2.5% mortality rate

People <65 more than 99% of deaths

Typically see a U shaped curve with Influenza: Infants and the elderly

Spanish Flu targeted mid-aged individuals more than others: cytokine storm

Question 6

Most pandemics we have seen are ______________________ rather than new variants

Answer 6

Most pandemics we have seen are recombination of old influenza strains rather than new variants

Question 7

______________________: Reporting of influenza like illness in the community

Answer 7

Sentinel GP Influenza like illness (ILI): Reporting of influenza like illness in the community

Question 8

Clinical Manifestations/complications of Influenza

Answer 8

Question 9

Diagnosis of Influenza?

Answer 9

Diagnosed primarily by PCR

Not often done for diagnostic purposes as too slow and labor-intensive, only used for antigenic development

Question 10

Treatment of Influenza?

Answer 10

Neuraminidase inhibitors prevent cleavage of viruses from the cell preventing its replication and spread

Neuraminidase cleaves hemagglutinin is what binds to cell and allows virus to replicate

Question 11

Prevention of Influenza?

Answer 11

Vaccination important

Injected is inactivated, cannot give you influenza

For infants, attenuated virus inhaled

More affective as delivered in same means as infection => Leads to further mucosal iGA immunity

Vaccine Selection:

Vaccine production takes ≈6 months, so vaccine virus strains are chosen:

End of February for Northern Hemisphere season

End of August for Southern Hemisphere

Protection from vaccine only lasts about 6 months

Question 12

Influenza Spread

Answer 12

Transmission by Respiratory droplets

Infectious period begins the day before symptoms