The virus apparently emerged in Wuhan, China. How does a virus that starts in one place spread around the world?
The short answer is that we live in a global economy that includes frequent domestic and international travel, and viruses often hitch rides with us.
Viruses, like other pathogens, don’t produce symptoms as soon as they come into contact with humans. First, they go through an incubation period, or a period of time when the virus multiplies to a threshold necessary to produce symptoms in its host.
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