In 1958, scientists at the CDC made their first trip overseas. A team went to Southeast Asia to respond to an epidemic of smallpox and cholera.

Since then, the CDC has been active throughout the world, following infectious [diseases] such as smallpox, polio, tuberculosis, AIDS, and SARS.

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So where did this killer flu come from? In 2005, researchers at the CDC announced that it had probably started off as a bird flu and then jumped to humans.

Does that sound familiar? The Spanish flu is very similar to the bird flu we see today. Some scientists believe it’s the same strain of influenza.

What do these two passages have in common?

Both mention the Spanish flu.
Both mention smallpox.
Both mention places the CDC travels to.
Both mention diseases the CDC studies.