Influenza Flashcards
When does seasonal influenza occur in the northern hemisphere?
Winter months (Dec- Feb)
When are severe epidemics of influenza observed periodically?
Every 11 years
What type of virus is influenza virus?
RNA
What are the 3 main groups of influenza?
A,B,C
What type of influenza only infects humans?
B & C
What H antigens are detected in humans?
H1-3
H18
What is the name given to the mechanism of genetic variation within the virus?
Antigenic drift
What is antigenic diff?
Point mutations in the genes coding for antibody binding sites. No longer recognised by immune system
What is an antigenic shift?
An abrupt major change in the virus, resulting in new antigen
How can antigenic shift occur?
When 2 different strains of a virus combine to form a new subtype
What can lead to a pandemic?
Antigenic shift
What is the difference between seasonal flu & pandemic flu?
Ordinary outbreaks occur every year during winter months whilst pandemics can occur at any point in year and are less frequent.
What % of the population is affected by seasonal flu?
10-15%
What % of the population is affected by pandemic flu?
25% +
Which type of flu, seasonal or pandemic, is usually more serious?
Pandemic
What are the requirements for pandemic flu?
Human pathogenicity
New virus (antigenic shift)
Efficient person -to -person transmission
What strand of flu demonstrated a pandemic in 09?
H1N1
What population will usually be affected by seasonal flu?
Young & old
What population will usually be affected by pandemic flu?
Usually young healthy individual, in addition to extremes of age
How does avian flu spread?
Direct contact with infected birds, dead or alive
Close human to human cnotact
What are the main types of avian flu?
H5N1
H7N9
How long is the incubation period of flu?
2 - 4 days
What other clinical features are observed in flu?
Abrupt fever Cough Myalgia Headache Malaise Sore throat
What is the WHO definition of flu?
Fever (>38) AND
cough
Onset within last 10 days
What does SARI stand for?
Severe Acute Respiratory Infection
What are some of the mechanisms of transmission of flu?
Airborne (person to person)
Contact (direct or indirect)
When can viral shedding of flu occur?
First 4 days (longer in children & immunocompromised)
How long can the influenza virus survive on non-porous surface?
24-48hrs
How long can influenza survive on porous surface?
8-12 hours
How are those at high risk of complicated influenza?
Patients with chronic illnesses Diabetics Immunocomprimised >65yrs Pregnant Children < 6 months Obese
What are some of the acute respiratory complications of flu?
Acute bronchitis
Secondary bacterial pneumonia
What are the most common bacteria which cause pneumonia?
S. pneumonia
S. aureus
H. influenzae
What are some of the less common complications of flu?
Primary viral pneumonia
Myocarditis/ pericarditis
Guillain-Barre
What investigations can be done in influenza?
Viral nose & throat swabs CXR Blood culture Pulse oximetry RR U & Es, FBC, CRP
What assessment score can be used as a prognostic factor for pneumonia?
CURB-65 Confusion Urea>7 Respiratory rate >30 Blood pressure (diastolic <60) >65 yrs of age
What are the names of neuraminidase inhibitors?
Oseltamivir
Zanamivir
When should antiviral therapy be used in flu?
Within 48hrs of symptoms onset
What are some of the adverse affects of tamiflu?
Nausea
Vomiting
Diarrhoea
Abdominal pain
Can oseltamivir be used in pregnancy?
Yes
When does an individual become non-infectious?
24hrs after last symptoms or when antiviral therapy complete
Longer in immunocompromised/ young
What protection should be worn by healthcare worker in cases of flu?
Surgical face mask
Plastic apron
Gloves
FFP 3 respirator
What type of vaccination is the seasonal flu vaccine?
Inactivated vaccine
Why should healthcare workers have the flu vaccine?
To protect themselves & family
Reduce risk of at risk patients
Reduce absence from work
