Orthomyxoviridae

Question 1

What does orthomyxoviridae mean?

Answer 1

(myxa – mucus)

Question 2

Morphology

Answer 2

-ssRNA genome
segmented (8)
helical capsid

enveloped

~100 nm

Question 3

Resistance

Answer 3

weak

Question 4

Biological properties

Answer 4

Baltimore V - viral transcriptase enzyme

proteins (genes on separate segments):

core: nucleoprotein (NP), polymerase (PA, PB1, PB2)

matrix (M1) protein

envelope: hemagglutinin (HA), neuraminidase (NA), matrix (M2)

virulence (H5, H7) ~ basic aa. at the protease cleavage site

Influenza A - euryxen, zoonotic; B and C: mainly humans

Question 5

Antigenetic properties

Answer 5

core and matrix proteins: conservative genes – A, B, C, D genus

envelope proteins (HA and NA): hypervariable genes
•HA: 16 serotypes
•NA: 9 serotypes

Antigenecity is determined by the HA and NA combination!

Identification codes: A/equi/Prague/1/56(H7N7)

Antigenic drift: mutations in the HA and NA antigens

Antigenic shift: recombination resulting new HA-NA combination

Question 6

Genus

Answer 6

Influenzavirus A, B, C, D
Thogotovirus
Quaranjavirus,
Isavirus genus

Question 7

Influenza A

Answer 7

Euryxen

Influenzavirus type A
- fever, respiratory symptoms, muscle pains

- relative species adaptation:
• porcine influenza (H1N1, H3N2) 
• equine influenza (H7N7, H3N8)
• avian influenza (all types, several combinations)
 (H5N1

Question 8

Influenza B

Answer 8

• human influenza

* B: seals

Question 9

Influenza C

Answer 9

Human influenza

C: dogs, swine

Question 10

What is antigenic drift?

Answer 10

These are small changes in the genes of influenza viruses that happen continually over time as the virus replicates

Question 11

Diagnosis

Answer 11

isolation (embryonated eggs) + HA test
indirect: HAI
PCR

Question 12

Avian influenza

Answer 12

Influenza A type.
H5N1 → human disease – after massive infections

H7N9
• first human case: China, 19. 02. 2013 → † 03. 04.
• so far more than 120 cases, ~ 25% mortality
• low virulence in birds!

Question 13

Thogotovirus

Answer 13

Tick-borne orthomyxo-like viruses

Arbor virus, tick vector
Viruses: thogoto virus, batken virus, dhori virus
Asia, Africa

Question 14

Isavirus

Answer 14

Infectious salmon anemia virus (Norway)