Influenza Flashcards
Describe influenza
Commonly known as the flu
Transmissible respiratory disease
Generally seasonal
2-8 days, usually resolved
What are typical symptoms of influenza?
Sudden high temp of 38C or above
Aching body and/or muscle soreness
Feeling tired or exhausted
Runny nose
Dry cough
Sore throat
Headache
Difficulty sleeping
Loss of appetite
Diarrhoea or tummy pain
Feeling sick and being sick
What is excess mortality?
Mortality associated with seasonal influenza
Mortality is age-related for seasonal influenza
What causes influenza?
Viruses
Describe influenza viruses
A, B and C viruses
A and B can cause severe illness in humans
C only causes mild illness
Describe Influenza A virus
Many antigenically distinct types of influenza A viruses
18 known subtypes of haemagglutinin (HA)
11 known subtypes of neuraminidase (NA)
Serotype of a flu strain is given as HxNy (e.g. H1N1)
What serotypes of influenza A circulate in pigs?
H1N1
H1N2
H3N2
What serotypes of influenza A circulate in horses?
H7N7
H3N8
What serotypes circulate in dogs?
H3N8
H3N2
Describe avian respiratory disease
All H1-H16 viruses are enteric pathogens of birds and some cause avian resp disease
Some serotypes of avian flu are much worse than others - current bird flu is H5N1
Birds fly and migrate and defecate
Avian flu virus can cause spillover infections into other species, including humans
How is flu transmitted?
Human to human via:
- respiratory droplets
- direct contact
- contact with fomites - objects or materials which are likely to carry infection e.g. clothes, furniture, utensils
Why do we get flu more than once?
Antigenic drift - antigens expressed by the virus can have mutations that lead to emergence of new strains each time so the host must produce new antibodies each time they are infected as they become infected with different strains
What is the difference between antigenic drift and shift?
Antigenic drift is accumulation of mutations
Antigenic shift is intermixing of RNA from influenza viruses from different species
