By Jonathan Blake
Newsbeat reporter in Mexico City
The Mexican capital's streets are deserted as the government shuts down schools, colleges and restaurants and advises people to stay at home, in an attempt to combat the spread of swine flu.
If people have to leave home, they are being advised to wear a surgical mask
From the window of the aeroplane, the sprawling buildings of Mexico City disappear into the distance below.
Cars are driving through the streets, but one passenger says there are far fewer than normal.
Stepping off the aeroplane and into the city at the centre of the swine flu outbreak, the first thing you notice is people wearing masks.
At the airport, in cars, in shops and on the streets.
Wandering through the Zona Rosa, where teenagers and young adults hang out in the evening, Anna Kristina, 20, and her friend Fatima, 23, are taking no chances.
"It's uncomfortable but it's the only way to prevent it," said Anna. "If you cannot stay home you should take precautions."
They would normally be at university but all schools and colleges are closed.
"Normally at this hour, the city is packed but now people are staying at home. That is a good thing," Anna said.
Others seem less concerned.
Aramis Oliver, also a student, has his mask hanging around his neck.
"I'm not worried really because I think here in Mexico we can control it," he said. "Right now it is out of control but I think we're going to be OK."
As we talk, the shutters are coming down on a cafe across the road.
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The owner, Rafael Savedre, says he is following orders and closing down for several days.
"We are losing business," he explained, "but we think we have to help, to support the decisions of the government."
Not far away at Boomers Grill And Bar, Ingrid Lopez Garcia, 23, is enjoying a drink with a friend as staff stack the chairs around them.
"We are relaxed," she said.
A box of face masks for customers is on the table next to her, but she prefers not to wear one.
"I don't need that. Maybe later, I don't know."
Forced to work
Adverts on the TV, on radio and on posters around the city tell people to sneeze or cough into their elbow, wash their hands regularly and stay at home if they get sick.
Traffic on the roads is much quieter than usual
But for many, like 23 year old Norma Olbera, it is not that easy.
"You have to come in, you have to do your work," she said. "And if you get sick, you'd better be very sick because if not you have to keep working every day."
Although Norma is not worried, she says many of her friends are concerned.
"They think it's going to happen, they think they're going to die. You just have to relax, you take your precautions but also be calm."
Some are frightened, some are relaxed, but nobody has any idea how bad the swine flu outbreak is, or how long it will be until they can get back to normal.