The swine flu has also been reported in the western United States. There have been six cases in California and two in Texas. All patients recovered.
But in Mexico at least 16 people have died. And 44 more deaths there could be the result of the swine flu.
The Mexican government is warning people to stay inside their homes. And on Friday night, a young woman from Naperville is following that advice.
Mari Bolyanatz lives just outside Mexico City. ABC7 talked to her a short time ago on Skype and asked her about being in Mexico during this outbreak.
"It's sort of like an unofficial quarantine, people are just being encouraged to stay in their homes," said Bolyanatz.
So Mari Bolyanatz is staying indoors for now. The Fullbright Scholar is usually busy with her students, teaching English.
On Friday, with the flu scare she briefly ventured out to the grocery store.
"I went out around rush hour. There should have been a bunch of traffic but it felt like a ghost town, like out of old westerns," said Bolyanatz.
Bolyanatz lives outside Mexico City. Throughout the area, schools, libraries, museums and state-run theatres are shut down.
It's a scene U.S. officials are following closely, especially since cases are now being reported in the United States.
"We do not know whether this swine flu virus or some other influenza virus will lead to the next pandemic. However, scientists around the world continue to monitor the virus and take its threat seriously," said Dr. Richard Besser, Centers for Disease Control & Prevention.
That includes Dr. Mark Dworkin of UIC who has just finished a book on outbreaks. He says, if you feel sick see a doctor, if necessary, and stay home.
"You don't want to send yourself out among others when you're ill like that, especially with a fever illness. That doesn't mean you've got the swine flu. That's the way it should be in general," said Dr. Mark Dworkin, University of Illinois at Chicago.
In the meantime, returning tourists are on alert.
"I'm definitely going to watch for myself and I would watch for my baby," said Tonya Horton, Returning from Mexico.
And the same goes for Bolyanatz.
"I was planning to go into Mexico City on Sunday for a birthday party of a friend. I mentioned that to a few friends, they were like, 'no, don't even think about it. Don't do it! Don't put yourself at risk,'" said Bolyanatz.
In the past, people have caught this flu from pigs. This, however, is a new strain of swine flu.
On Friday health officials said they're concerned because this strain includes swine, avian and human viruses. And it appears to be transmitted from human to human.