Influenza

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Influenza

Ieuan Davies

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Signs and Symptoms

Influenza is an acute, viral respiratory infection.

Fever, chills, headache, aches and pains throughout the body, sore throat which may lead to bronchitis or pneumonia.

Vomiting and diarrhoea may also occur.

Many deaths have been attributed to influenza

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Influenza Pandemics

A pandemic is a world wide spread of infection occurring in many countries simultaneously.

Flu pandemics occur approximately every thirty years.

Flu pandemics occur because a new strain of the virus emerges for which people have no immunity and there are no vaccines available.

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Pandemics

New flu viruses occur due to mutation

Mutation occurs because different strains of influenza virus can exchange genes by infecting different animals

Avian influenza viruses can exchange genes with human influenza viruses creating hybrid strains

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1918 - 1919 pandemic

This killed between 20 – 40 million people

Face masks were worn but provided little protection against infection

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Cause

The cause of influenza is the influenza virus.

Influenza A, B and C viruses are found

Influenza A viruses are associated with serious illness and pandemics

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Influenza virus

The flu virus is an RNA virus

The genome codes for five viral proteins and is made of eight fragments.

The virus has a lipid envelope with two glycoproteins present

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Flu virus glycoproteins

Haemagglutinin - this glycoprotein plays a part in infection and provides the “H” in the strain type.

Haemagglutinin attaches the virus to cells and allows the viral envelope to fuse with the cell membrane and enter cells.

Neuraminidase – has a mushroom shape, its role is to allow the release of viruses to infect other cells

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HN terminolgy

H refers to Haemagglutinin types and each is given a number H1, H2 etc,

Neuraminidase is designated N and different forms are available as well e.g. H5N1 (avian) and H1N1.

Different combinations of H and N glycoproteins give rise to different strains