Influenza, Pandemics & Other Respiratory Infections Flashcards
Where did influenza come from
Zoonotic
Genera of influenza & which are more common in humans
A, B, C
A&B main human pathogens
Subdivision of influenza A
Subdivided by 2 surface antigens:
- Haemagglutanin (15 subtypes)
- Neuraminidase (9 subtypes)
All 15H and 9N have been detected in birds.
E.g. H1N1
Why can influenza change/mutate
Can get gene reassortment in infections
Gene swapping can occur during co-infection with human and avian flu virus
No proof reading mechanism so prone to mutation
What causes seasonal flu epidemics?
Minor antigenic variation = antigenic drift
What causes flu pandemics
Gene re-assortment & major antigenic variation = antigenic shift
Where does gene re-assortment often occur for flu
Animal (pig) reservoir- get bird virus and human virus at same time –> viruses combine –> new virus adapted to spread rapidly in humans
Or virus straight from bird –> human (human reservoir)
How do humans promote zoonotic infections
Humans in close proximity to animals - wet/live markets etc.
Intensive farming: bringing lots of animals in close proximity to each other
Farm parks/zoos
Influenza A
Can infect pigs, cats, horses, birds, sea mammals, humans
Causes severe & extensive outbreaks and pandemics
Influenza B
Tends to cause sporadic outbreaks (schools, care homes, garrisons) that are less severe
More often seen in children
Like A - prone to mutation
Influenza C
Relatively minor disease
Mild symptoms or asymptomatic
Influenza transmission
Mainly via aerosols generated by coughs & sneezes.
Possible via hand-hand contact, other personal contact & fomites
Influenza infection symptoms & complications
Upper +/- lower respiratory tract symptoms + fever, headache, myalgia, weakness
Complications: include bacterial pneumonia, life threatening
People with higher risk of flu mortality
Underlying medical conditions
chronic cardiac & pulmonary diseases
old age
chronic metabolic diseases
chronic renal disease
immunosuppressed
Influenza treatment
Supportive care (oxygen, hydration, nutrition, maintain homeostasis, prevent/treat secondary infections)
Antivirals: reduce risk of transmission, reduce severity and duration of symptoms (only really see a difference at a population level)
Seasonal flu
Antigenic drift every year - so can infect people who were immune to last years varient.
Usually peaks December - March (northern hemisphere)
Southern hemisphere - analyses their strains to make predictions for vaccines
Avian Influenza - about
Avian pathogen but can transmit to humans.
Usually mild in birds but can mutate to 100% mortality form.
~50% death rate in humans
HIgh risk of becoming pandemic
How to control avian influenza
Cull affected birds
Biosecurity & quarantine (e.g. 5-10km around a farm)
Disinfect farms
Control poultry movement
Vaccinate workers with seasonal flu jab
Antivirals for poultry workers
PPE
Try to reduce chance of coinfection
What is the number 1 risk to UK
Pandemic flu
Reasons for more pandemics
More travel
More people
Intensive farming (more animal contact with humans & factory farming)