3. When and where did it start?
The virus may have mutated into its current form months or even a year ago, and it happened, well, somewhere in the world.
The first symptoms started to show up in early March in the Mexican state of Veracruz, an area with a number of pig farms. The earliest confirmed case was a 5-year-old boy, one of hundreds of people in the town of La Gloria whose flu symptoms left them struggling to breathe.
People from La Gloria kept going to jobs in Mexico City despite their illnesses, and could have infected people there.
Still, there's no guarantee the virus came into existence in Veracruz. It spreads so easily, it could have made its way to Mexico from just about anywhere.
Some Mexican officials have offered some other suggestions of places where the virus may have begun, such as China, Pakistan or Bangladesh. But the fact is that the flu's origin remains a mystery.
Fortunately, it also doesn't really matter ? the outbreak has made its way around the world, and nothing can be done now at the point of origin to slow it down.
