The threat of a flu pandemic gripped the world on Monday, as a virus that has killed 103 people in Mexico and shut down chunks of the capital spread to the United States and as far as New Zealand.
The dollar weakened along with Mexico's peso as Asian markets were rattled by an outbreak that ballooned over the weekend, prompting the World Health Organisation to activate its 24-hour 'war room' command center.
No deaths have occurred outside Mexico from the new strain of swine flu but 20 cases have been identified in the United States and six in Canada. Possible cases are being checked as far afield as Europe, Israel and New Zealand.
Mexico, a major exporter of oil, coffee and factory goods, faced a week unlike any before as schools were closed in several states in order to slow the spread of the virus and the densely populated capital ground to a halt. Mexico City's bars, museums and stadiums shut and many office workers were set to work from home as a precaution.
Many in the capital spent the weekend hunkered at home or wore blue surgical face masks handed out by truckloads of soldiers to venture out onto strangely hushed streets. The city government mulled halting public transport.
"The idea of spending 10 days in the house with two small children, with no cafes, no museums, is totally unappealing so I'm going to San Diego," said an American expatriate, CR Hibbs, who was headed out of the city with her kids.
Health Minister Jose Angel Cordova said late on Sunday that the flu had killed 103 people in Mexico and about 400 people were hospitalized.
A glimmer of hope was that most patients had recovered.
The new flu strain, a mixture of various swine, bird and human viruses, poses the biggest risk of a large-scale pandemic since avian flu surfaced in 1997, killing several hundred people. A 1968 Hong Kong flu pandemic killed about 1 million people globally.
The United States declared a public health emergency on Sunday. Although most cases outside Mexico were relatively mild, a top official at the Centers for Disease Control and Prevention, said she feared there might be U.S. fatalities.
Mexico, whose government already is grappling with a murderous drug cartel war and a slumping economy, faced a dent to its economy with shoppers and diners expected to stay home this week.
Mexico City Mayor Marcelo Ebard said closures in the capital could last 10 days. Far away in the Pacific party-town of Acapulco, hundreds of nightclubs were shuttered.
One of the country's biggest annual fairs, the Feria San Marcos, was axed in the central city of Aguascalientes, in a bitter disappointment to fans of its raucous bullfights, free-flowing alcohol and blaring folk music.
The Roman Catholic faithful were stuck home too as church doors were shut and masses were broadcast on radio and television. Baptisms and confirmations were canceled and church authorities mulled rescheduling weddings.
Finance Minister Agustin Carstens said the flu's impact would be "transitory" but the peso, already weakened by the economic crisis, fell nearly 3 percent in electronic trading on Sunday night.
The World Health Organisation has declared the flu a "public health emergency of international concern" that could become a pandemic, or global outbreak of serious disease.
That could cost trillions of dollars to a world economy already in its worst crisis in decades.
Flu is characterised by a sudden fever, muscle aches, sore throat and dry cough. Victims of the new strain have also suffered from vomiting and diarrhea.