Download H-what N-who? - How are viruses named?

H-what N-who? - How are viruses named?
This diagram shows a simplified cartoon of an influenza virus showing the neuraminidase and haemagglutinin
molecules on the surface of the virus particle and the nuclear protein within in. The nuclear protein contains
RNA. Differences in the nuclear protein give rise to the different subtypes of influenza ie A, B and C.
A single virus particle will have approximately 500 molecules of haemagglutinin on its surface and about 100
molecules of neuraminidase. The haemagglutinin and neuraminidase molecules on the surface of the virus
particle are the parts of the virus that are different in different subtypes of the virus. It is after the different
variants of these that the flu viruses are named eg H1N1 viruses have the type of haemagglutinin (H)
designated as 1 and the neuraminidase (N) designated as 1. The haemagglutinin molecule is very important in
causing infection as it is this part of the virus that binds to the host cells. The immune system mounts a
response to both the haemagglutinin and neuraminidase surface molecules. Changes in these molecules mean
any previous immunity may not be effective against infection with a new or different subtype.
Using the following cartoons to represent H and N molecules complete the different subtype of virus
below:
Virus particle 1: H1N1
This subtype caused the 1918 “Spanish Flu” pandemic. It is
thought to have caused between 50 and 100 million
deaths. This is more than the number of people who died
during WW1. Unlike seasonal flu, this pandemic flu caused
high rates of illness and death in the young, fit and healthy
population. Seasonal flu tends to only kill the very young,
very old or people who already have another illness.
Virus particle 2: H2N2
This subtype caused the "Asian Flu" pandemic in the late
1950s. The pandemic started in Asia in 1957 and spread to
every part of the world within a few months. There was a
much better understanding of influenza in the 1950s
compared to 1918. The virus was isolated quickly and
identified as a new subtype. However vaccines were not
produced fast enough or in enough quantities to be very
effective. Between 1 and 4 million people died during the
pandemic.
Virus particle 3: H3N2
This subtype cased the "Hong Kong Flu" pandemic in
1968. The pandemic started in Asia and spread across the
world. The virus was rapidly identified as a new subtype
and the world was warned of a possible pandemic. This
pandemic was milder than the one in 1957 - it may be that
some people who were infected during 1957 had partial
immunity to the shared N2 subtype. Around 750,000
people are thought to have died.