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What Caused Swine Flu?

To figure out what was causing swine flu, Richard Shope took bacteria
from the spit of a sick pig and injected them into a healthy pig. When
the second pig did not become sick, he knew the flu was not an infection
caused by bacteria. He then took the bacteria out of the pig spit and
injected the remaining substance into the healthy pig. The pig became sick,

proving that something other than bacteria caused the disease.

Identifying the Enemy

Shope’s finding was quickly followed by the isolation of the influenza virus
from humans by a team of virologists at the National Institute for Medical

Research in the United Kingdom (UK). In 1933, Wilson Smith, Christopher
Andrewes, and Patrick Laidlaw transferred human antigens, which were
not bacteria, to ferrets. The ferrets became infected with the flu. This
helped the team identify the antigen as a virus. A virus was described

as an antigen that was too small to be seen. It could be filtered, and still
produced disease, even though it could not reproduce on its own.

Today, thermal cameras can be
used to detect pigs that have a high
body temperature and therefore
are likely to have swine flu.

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