Influenza Flashcards
What type of virus is the influenza virus?
RNA virus
8 segment genome
What are the 3 main groups of influenza virus?
A, B, C
What type of influenza infects mammals and bird/?
IfA
What type of influenza infects only humans?
IfB and IfC
What are the main surface proteins on the influenza virus?
Haemagglutinin
Neuraminidase
What does the surface protein haemagglutinin do?
Facilitates viral attachment and entry to host cell
What does the surface protein neuraminidase do?
Enables new virion to be released from host cell
How many different known H antigens are there?
18 differed H antigens
How many different known N antigens are there?
11 different N antigens
What virus family is influenza part of?
Orthomyxoviridae
How does antigenic drift work?
Occurs continually over time, small on-going point mutations in the genes coding for antibody binding sites
Does antigenic drift or shift change the antigenic properties and eventually means the immune system can’t combat the virus as well?
Antigenic drift
Does antigenic drift or shift cause worse than normal epidemics and vaccine mismatch?
Antigenic drift
What is antigenic shift?
Abrupt major change in the virus, resulting in new H/N combinations
Each year, what does the flu vaccine contain?
Two A strains
One B strain
- can change year to year
What is the genetic change that enables a flu strain to jump from one animal species to another?
Antigenic shift
What is the process by which two or more different strains of a virus combine to form a new subtype, resulting in new H/N combinations?
Antigenic shift
What can lead to pandemics: antigenic drift or shift?
Antigenic shift
How is pandemic flu different to seasonal flu?
Occurs sporadically
Affects 25%+ of population
More serious, more complications
How much of the population does seasonal flu usually affect?
10-15%
What are pandemic requirements?
Human pathogenicity
‘New’ virus (antigenic shift)
Efficient person-to-person transmission
Who is more susceptible to the flu?
Young and old
How does avian flu spread?
Direct contact with infected birds: dead or alive
Occasional transmission via close human contact
Not food
What are the clinical features of influenza?
Incubation period 2-4 days
Abrupt fever up to 41’ lasts 3 days
Plus 2 or more of: cough, sore throat, myalgia, headache, malaise
Predominance of systemic symptoms
What are less common symptoms of influenza?
Nausea, vomiting, diarrhoea
What is an ILI?
Influenza-like illness
What is the WHO definition for an ILI?
Fever >38’ AND
cough
onset with last 10 days
What are the symptoms of swine flu?
Sudden fever
Sudden cough
Tiredness, chills
Headache, sore throat, running nose, sneezine
Diarrhoea, stomach upset, loss of appetite
Aching muscles, limb or joint pain
What is the transmission of influenza?
Airborne: Person -> person (droplets >5 microns)
Contact: direct, indirect
What is the period of virus shedding?
First 4 days of illness
Longer children+immunocompromised
What is the virus survival?
24-48hrs non-porous surfaces
8-12hrs porous surfaces (tissue)
What are high risk groups for influenza?
Chronic organ disease DM Immunosuppression 65+ Pregnancy Children <6mo Morbid obesity
What are common respiratory complications of influenza?
Acute bronchitis
Secondary bacterial pneumonia
What are less common complications of influenza?
Resp: primary viral pneumonia
Cardiac: myocarditis/pericarditis
CNS: transverse myelitis/Guillain-Barre
How does encephalitis lethargica present?
Fever, headache
External ophthalmoplegia
Lethargy
Sleep reversal
What are the investigations for influenza?
Viral nose and throat swabs Chest XR Blood culture Pulse oximetry RR U&Es, FBC< CRP
When are patients at risk of secondary bacterial pneumonia and should have urgent CXR?
Flu symptoms and fever for >4 days
What does the CURB65 score stand for?
Confusion Urea >7mmol/l RR BP >65
What class of drugs are commonly used for influenza?
Neuraminidase inhibitors
antiviral therapy
What are examples of neuraminidase inhibitors?
Zanamivir
Oseltamivir (Tamiflu)
What is the common name for oseltamivir?
Tamiflu
What is the management for influenza?
Antiviral therapy - Tamiflu or Relenza
What are the common ADR for Tamiflu?
Nausea, vomiting, abode pain, diarrhoea
What is the first line therapy in a pregnancy influenza?
Tamiflu
When does an individual become non-infectious with influenza?
24hrs after last flu symptoms or when anti-viral therapy completed
