orthomyxoviridae + paramyxoviridae

genomics of orthomyxoviridae

• negative sense ssRNA viruses

• segmented genome: allows for rearrangments

what is influenza and common symptoms

• respiratory infection

• muscular: extreme tiredness

• joint aches

• upset stomach

transmission of influenza

through the air or infected birds droppings

is influenza enveloped?

yes

spike proteins of infleunza

HA- hemagglutinin

• binds to sialic acid receptors

• mediates membrane fusion

NA- neuraminidase

• cleaves sialic acid residue

• helps virus to exit infected host cells

• breaks down mucins in the respiratory tract to help spread

what is antigenic drift and its outcome?

• slow change throughout the genome due to point mutations in multiple antigenic sites of HA bc of error-prone RNA-dependent RNA polymerase

• not neutralized by original antibodies and vaccine no longer prevent disease

• outcome: seasonal flu requires new vaccine each year

what is antigenic shift and its outcome?

• dramatic change in the genome due to reassortment of HA and NA genes by segmented genomes

• resulting virus has new antigenic properties and humans have no protection

• outcome: epidemic/ pandemic

key to influenza binding

proteoglycans on the cell surface that terminate in sialic acid

• human respiratory tract has different types of sialylated glycans that allow for the binding of different types of influenza

characteristic of praramyxoviradae

• non-segmented

• negative sense ssRNa

• enveloped

• focus: mumps and measles

difference between orthomyxoviridae and paramyxoviridae

• no segmented genome or NA in paramyxoviridae

result of transcriptional polarity

• single promoter model

• the further downstream genes are from the leader sequence, the less they will be transcribed by RNA polymerase

• too much of the upstream proteins

clinical symptoms of mumps

swelling of one of both paratid glads

Mumps transmission and treatment

• respiratory droplets and direct contact

• vaccine available

diagnosis of measles

small white spots, koplik’s spots, inside the mouth

measles transmission and treatment

• highly contagious; respiratory droplets

• vaccine

define R₀

number of people one sick person will infect

• measles have the highest

what makes measles so contagious?

• infects lung epithelial cells

• spreads systemically

• aerosolized as cough or upon exhalation

• can remain airborne for 2 hours

• contagious for 8 days prior to symptom onset

• infectious dose very low (R₀ is high)