What is one of the most common causes of respiratory infections?
influenza
What is the significance of influenza?
it causes high rates of morbidity and mortality
What are the most common causes of influenza like illness (ILI)?
Influenza A and B
Aside from Influenza A and B, what are other causes ILI?
influenza C
parainfluenza virus
RSV
mycoplasma pneumoniae
How is influenza spread?
inhalation of droplets (coughing, sneezing)
direct or indirect contact with contaminated resp secretions
What is the incubation period of influenza?
1.5-2 days (range 1-4)
How long can an adult influenza-sufferer spread influenza?
one day before symptoms to approx 5 days after onset
Which group of people might be infectious longer with influenza?
children
immunocompromised
What is the “normal” season for influenza?
november-april
peaks in winter months
Describe the biology of influenza.
negative strand RNA virus covered with protective envelope
each RNA segment is encapsulated by nucleoproteins which forms a ribonucleotide-nucleoprotein complex (RNP)
What covers the lipid envelope of influenza?
haemagglutinin (HA)
neuraminidase (NA)
matrix 2 (M2) ion channels
What is the antigenic portion of influenza?
HA
NA
M2 ion channels
Describe the steps in the invasion and replication of influenza?
What happens to a host cell after a new virus is released?
the cell dies
What is influenza antigenic shift/drift?
appearance of influenza (usually A) with new HA or NA subtypes
What is the impact of influenza antigenic shift on our immunity to influenza?
variations within a subgroup may be so different that immunity to one related strain may not mean immunity to others
immunity to one subtype does not protect against other subtypes
Why are influenza vaccines reformulated every year?
antigenic shift
-based on changing patterns of the virus
What causes influenza antigenic shift?
mutations during replication
-the virus has no proof reading
True or false: nearly every newly-manufactured influenza virus is a mutant
true
What is cited as being the most devastating epidemic ever?
influenza pandemic of 1918-19
-infected 20% of the world population
-mortality rate of 2.5-20%
-most deadly for people ages 20-40
-killed up to 50 million
Which pandemic occurred in 2009?
H1N1 pandemic
-the latest influenza pandemic
-began in mid April 2009, peaked in first 3 weeks of June
What are the signs and symptoms of influenza?
sudden onset of:
-high fever (usually chills first): lasts 7-10 days
-cough (may persist for 2 weeks)
-sore throat
-myalgias and fatigue (can be severe and may linger for
weeks)
-headache, loss of appetite, coryza, N, V, D (esp kids)
How long does it take most people to recover from influenza?
7-10 days
What kind of infection is influenza?
acute respiratory tract infection
-NOT GI INFECTION