Virology: Orthomyxoviruses & Paramyxoviruses

Orthomyxoviruses

influenza

Human Influenza: Types

A, B, C

Type A

subtypes
wide host range
8 segments
has ability to switch species

Type B

human only
8 segments

Type C

humans and pigs
7 segments
-HA and NA one gene
very mild symptoms

Influenza A: characteristics

negative-sense RNA
segmented genome
-key to pandemics
-multiple viruses coming to host cell

Influenza A: wide host range

water fowl & poultry, humans, pigs, dogs, horses, cats
intermediate hosts
-adaptation
-reassortment
-maintenance

Adaptation

mutations
duck --> turkey, pig, chicken --> humans (naive population)

Reassortment

mixing vessel for different viruses to come together to create something novel
ducks and humans --> turkey, pig, chicken --> human
(pandemic flu)

Maintenance

place for virus to be maintained until new naive population comes about (herd immunity)
human --> turkey, pig, chicken --> human

Influenza A: Zoonotic Transmission

most common are farmers and kids at county fair

Influenza A: HA

surface protein, spike protein: attachment to target cell
about 18-19 subtypes

Influenza A: NA

release
about 12 subtypes

Influenza A: subtypes

H5N1
H3N2
they are different antigenically
if you make a shot, need multiple components cause if you only have 1 then it will only target 1

Influenza A: swine origin

H1N1 virus
pigs from North America and Eurasia made a mixture of 4 different viruses (2009 pandemic)

Influenza A: treatment

vaccine: inactivated or live attenuated (cold adaptive)
-quadrivalent: a H1N1, H3N2, and B (2)
drugs

Influenza A: drugs

exit/release inhibitor (Tamiflu)
cap snatching inhibitor- replication inhibitor (Xofluza)
entry inhibitors
-rarely used--> natural resistance

Influenza A: Normal vs High path

low path (human strains) & high path (bird flu)

Low path

normal human strains
requires human enzyme for maturation
-enzyme only found respiratory tract in humansH

High path

"bird flu"
-lower infection than normal human flu
receptor usage? sugar structure in respiratory tract
temperature? warmer temps
cytokine storm?

Paramyxoviruses

measles, mumps, respiratory syncytia virus (RSV)

Measles: characteristics

-ss RNA virus, non-segmented
enveloped
--environment stable for a couple hours
human only

Measles: transmission

aerosol, fomite
can travel farther than most viruses (6 ft)

Measles: disease

acute infection
-rare: SSPE (subacute sclerosing panencephalitis)
Incubation: 7-13 days
natural infection--> lifelong protection/immunity
wipe immune memory
rash indicator--> immune-mediated
infects/resets the immune system
-immunocompromised
-secondary infection
Gender effect

Measles: gender effect

rash more prominent in males than females
higher lethality in females than males

Measles: passive immunization

works

Measles: vaccine

live-attenuated (MMR)
-boosters

Measles: drugs

none

Measles: prevention

vaccination

Mumps: characteristics

-ss RNA virus, non-segmented
enveloped
human only

Mumps: transmission

aerosol, fomite

Mumps: disease

acute infection, often asymptomatic
Incubation: 16-18 days

Mumps: passive immunization

does NOT work

Mumps: vaccine

live-attenuated (MMR)

Mumps: drugs

none

Mumps: prevention

vaccination

RSV: characteristics

-ss RNA virus
enveloped
human only

RSV: transmission

respiratory

RSV: disease

acute infection
Incubation: 4-5 days
age effect
no immune memory formed

RSV: age effect

adult: common cold
small children: necrosis of bronchi & bronchioles (bronchiolitis), major cause of croup

RSV: passive immunization

works
-not maternal antibodies

RSV: vaccine

none
-deleterious vaccines (worse disease upon exposure)
-RNA vaccine in clinical trials

RSV: drugs

none
-passive immunization
-open airways

RSV: prevention

avoid infected individuals