What is influenza?
- An acute (short) respiratory illness resulting from infection with an influenza virus
- Highly infectious and can spread rapidly from person to person
- Some strains cause more severe illness than others
- 1 of 3 types
What are the 3 types of influenza viruses?
- A viruses – infect birds and other animals, as well as humans – source of seasonal influenza epidemics and all pandemics (most significant, causes most illness and make the most unwell)
- B and C viruses – infect humans only and do not cause pandemics
Where does influenza A virus come from?
- Human influenza A viruses start as avian (bird) influenza viruses
- very difficult to spot and track (birds don’t get obvious symptoms)
- Moved from wild birds to domestic birds (that we eat/have as pets)
- Virus has receptors for human, pig, chicken and duck cells
What are the symptoms of influenza?
- Sudden onset
- Fever, headache, muscle aches, severe weakness
- Respiratory symptoms, e.g., cough, sore throat, difficulty breathing
How does influenza spread?
- Spreads easily from person to person through coughing and sneezing
- Transmitted by:
- inhaling respiratory aerosols containing the virus, produced when infected person talks, coughs, or sneezes
- touching an infected person or an item contaminated with the virus and then touching your eyes, nose, or mouth
How do symptoms of fly present in children?
Children present symptoms usually 2 days after they were in contact with the flu virus, those being; sudden fever, CHILLS, headache, muscle aches, dizziness, loss of appetite, tiredness, cough, sore throat, runny nose, N+V, weakness, ear pain, diarrhoea. People are contagious until their symptoms ae gone, about 1 week for adults but can be longer in children
What are the pulmonary complications of flu infection?
primaryinfluenzapneumonia, secondary bacterial pneumonia, pneumonia due to unusual pathogens or in immunocompromised hosts, and exacerbations of chronicpulmonarydiseases. morbidity and mortality
What is antigenic drift?
- Occurs among influenza A viruses resulting in emergence of new variants of prevailing strains every year
- Antigen is what gives us memory in our immune system, if it changes, our immune system will not recognise it
- New variants result in seasonal influenza each winter
- People who have already had flu could get it again
- Some years are worse than others – partly related to degree of ‘drift
- Large drift = brand new virus
No drift = unchanged, immunity from illness or vaccine remains
Very unpredictable
What is an influenza pandemic?
Influenza pandemics are worldwide epidemics of a newly emerged strain of influenza
Few, if any, people have any immunity to the new virus
This allows the new virus to spread widely, easily, and to cause more serious illness
What causes a pandemic?
Pandemics occur when a new avian influenza strain acquires the ability infect people and to spread easily person to person
This can occur in two ways:
- Reassortment (an exchange of seasonal and avian influenza genes in a person or pig infected with both strains)
- Mutation (an avian strain becomes more transmissible through adaptive mutation of the virus during human avian influenza infection)
What are major changes in antigenic shift in pandemic influenza?
Major changes occur in the surface antigens of influenza A viruses by mutation or reassortment
Changes are more significant than those associated with antigenic drift
Changes lead to the
emergence of potentially pandemic strains by creating a virus that is markedly different from recently circulating strains so that almost all people have no pre-existing immunity
Seasonal vs pandemic influenza?
New threat to humans
Social Disruption
Infect more people, cause more severe illness, and cause more deaths
Seasonal influenza viruses most often cause severe disease in the very young, the very old, and those with chronic illnesses
The highest mortality rate in the 1918-19 pandemic was in people aged 20-40 years
No idea when pandemic flu will happen
How are different types of flu viruses differentiated ?
Flu viruses have antigens on the surface (H): hemagglutinin - protein that allows the virus to stick to host
Neuraminidase (N) enzyme that allows it to invade the host cell
Different numbers and combinations are different types e.g. H1N1 = spanish flu, H2N2 = asian flu, HCN2 = hong kong flu
1918 flu pandemic
Highest mortality in people 20-40 years of age
- 675,000 Americans died of influenza
- 43,000 U.S. soldiers died of influenza
What are pandemic waves?
Past experience teaches us that following
the emergence of a new pandemic virus:
More than one wave of influenza is likely
Waves typically last 6-8 weeks
Gaps between the waves may be weeks or months
A subsequent wave can be worse than the first
What are the 5 stages of flu consultation?
STAGE 1: initiating the consultation - hello, how can I help?
STAGE 2: gathering information - describe symptoms, have you tried anything for symptoms? Any medical conditions? Etc
STAGE 3: shared decision making - options for management etc
STAGE 4: patient education - inform on dosage and administration, side effects etc etc
STAGE 5: close consultation - check patient is happy with everything, any questions?
What can be done to slow the spread of a pandemic?
Vaccine: not expected to be available until later in a pandemic (flu vaccine now available)
Antivirals: likely to be insufficient quantities, effectiveness unclear
Disease containment measures: may be the only measures available in the early stages of a pandemic. may be helpful in slowing the spread of a pandemic, allowing more time for vaccine production
Treatment of flu?
Oral oseltamivir and inhaled zanamivir (neuraminidase inhibitors)
Viral resistance to neuraminidase is inevitable
Alternative drugs for influenza treatment are urgently required
Inavir and favipiravir are showing priomise in clinical trials (2014)
What are disease containment measures?
Isolation: restriction of movement/separation of ill infected persons with a contagious disease
Quarantine: restriction of movement/separation of well persons presumed exposed to a contagious disease
Self-shielding: self-imposed exclusion from infected persons or those who may be infected
Social distancing: reducing interactions between people to reduce the risk of disease transmission
What are other methods to reduce transmission?
Hand hygiene (cleaning hands with soap and water or an alcohol-based hand rub)
Respiratory hygiene, e.g., “Cover your cough”
Cleaning and disinfection of contaminated objects, surfaces
Physical barriers (e.g., glass or plastic “windows” to protect front desk workers)
Use of personal protective equipment (PPE) in some settings (e.g., healthcare) such as gowns, gloves, eye, and respiratory protection
