The Mexican capital stayed on its feet on Monday despite a deadly flu outbreak that forced restaurants, gyms and even law courts to shut down in an effort to prevent spreading contagion.

One of the world's biggest cities, Mexico City is bearing the brunt of the swine flu virus that has killed up to 149 people nationwide, spread in the United States and raised fears of the world's first flu pandemic in over 40 years.

Some companies in Mexico City told their staff to work from home but banks were operating normally and most shops and businesses were open, even if employees complained about a lack of customers.

"No one told me anything so I've come as usual today," said Claudia Reyes, 27, who works in sales. "Some people are going to have to bring their children in to the office, which is a joke because they'll be at risk of infection here."

But empty stores and closed restaurants meant it was not quite business as usual in the country's capital.

"We haven't done anything all day, we haven't had a single client," said hairdresser Liliana Nieto, 29.

Traffic in the sprawling city of 20 million was brisk and workers, many wearing surgical face masks or covering their mouths with scarves, packed buses from the early hours despite fears about the risk of infection.