Influenza Flashcards
What kind of virus in influenza?
RNA virus
What are the 3 main groups of influenza virus?
A
B
C
What are the surface proteins of the influenza virus?
18 different H antigens
11 different N antigens
What is the purpose of H antigens?
Facilitate viral attachment and entry to host
What is the purpose of N antigens?
Enables new virus to be released from host cell
What is antigenic drift?
Continual change in antigenic properties and genetic variation
What is antigenic shift?
Abrupt major change in virus, resulting in new combinations due to reassortment of gene segments
What does antigenic shift allow for?
Flu strain can jump from one species to another
What are the methods of transmission of influenza?
Airborne via large droplets
Direct or indirect contact
When does virus shedding occur?
First 1-7 days
Longer in young and immunocompromised
What is the viral survival on porous and non porous surfaces?
Porous= 8-12 hours
Non porous= 24-48 hours
What is the seasonal flu?
Occurs every winter
Unplesant but not life threatening to healthy individuals
What is pandemic flu?
Occurs sporadically
Affects 25%+ of population, more serious and more complications
What are the requirements for a pandemic flu?
Human pathogenicity
Antigenic shift
Efficient transmission
How is avian flu spread?
Direct contact with birds or occasionally through close human contact
What are the risk factors for flu?
Neuro, hepatic, renall, pulmonary or chronic cardiac disease Diabetes Severe immunosuppression >65 Pregnancy Children <6months Morbid obesity
What is the incubation period of influenza?
1-7 days, usually 2-4
What can the fever be in influenza?
Up to 41, normally 38-40
How long does the fever last in influenza?
1-5 days
What is the clinical definition of influenza?
Abrupt fever of up to 41 plus 2 of
- cough
- myalgia
- headache
- malaise
What are the less common symptoms of flu?
N&V
Diahorrea
What investigations are dome for flu?
Viral nose and throat swabs FBC, U+E, CRP Blood culture Pulse ox CXR- if pneumonitis, pneumonia or ARDS
What is the treatment of flu?
Antivirals not always given
What are the common antivirals given for the flu?
Oseltamivir (Tamiflu)
Zanamivir
What is the treatment of flu in pregnancy?
Antivirals recommended, Tamiflu 1st line
What are the possible adverse effects of Tamiflu?
N&V, abdo pain, diarrhoea
Headache, hallucinations, insomnia, rash
What are the possible adverse effects of Zanamivir?
Rarely bronchospasm
What are the common respiratory complications of the flu?
Acute bronchitis
Secondary bacterial pneumonia
When does secondary bacterial pneumonia occur in flu?
4-5 days after flu onset
What is the CXR protocol in the flu?
Flu like symptoms and fever >4 days= urgent CXR
What are the less common respiratory complications in the flu?
Primary viral pneumonia
What are the cardiac complications of the flu?
Myocarditis
Pericarditis
What are the CNS complications of the flu?
Transverse myelitis
Guillain Barre
Myositis and myoglobinuria
When does flu become non infectious in immunocompetent adults?
24 hours after last flu symptoms or antiviral therapy completed, whatever is later
When does the flu become non infectious in immunocompromised adult and children?
Separate for each case
What is the flu vaccine?
Viruses grown in allantoic cavity of chick embryos, then clinically inactivated and purified
