orthomyxoviridae

orthos

correct/ right/ proper

myxa

mucus

orthomyxoviridae

cause influenza in human and animal

spikes

• peplomers

• surface projections of glycoproteins

2 types

• Haemagglutinin (H)

• Neuraminidase (N)

Neuraminidase (N)

cleaving viral receptors (release of virions from infected cells)

Haemagglutinin (H)

virus attachment (promoting entry of virus

target receptor

• sialic acid receptors (surface of epithelial cells in respiratory tract

Antibodies against H glycoprotein

– responsible for virus neutralization

genome

• 6-8 segments of linear, negative-sense- single- stranded RNA

4 genera

• Influenzavirus A

• Influenzavirus B

• Influenzavirus C

• Thogotovirus

Influenzavirus A

– most important; significant pathogen of animals and humans

Influenzavirus B and C

both human

thogotovirus

tick borne arboviruses

curretnly )2025)

• H1-H18

• N1-N11

2 mechanism

• responsible for emergence of new virus

• point mutation

• genetic reassortment

point mutation

• emergence of new strains;

• give rise to antigenic drift

genetic reassortment

• emergence of new subtypes; complex;

• antigen shift

classification of isolates

Influenza virus type/host/geographical origin/strain number/year of isolation/subtype

• E.g. A/equine/Prague/1/56 (H7N7)

antigenic drift

• Involves gradual, small changes in Influenza virus surface proteins (HA and NA)

• Require vaccine updates

Antigenic shift

• Rarer event

• Major, abrupt change resulting in new HA and/or NA proteins

• Potentially causing pandemics

LPAI

• low pathogenic

• Mild or no disease

• Most H1-H16

HPAI

• high pathogenic

• High mortality

• Some H5 and H7AI