Argentina is currently going through its peak annual flu season
The city and province of Buenos Aires have announced a health emergency to fight a swine flu outbreak that has killed at least 26 people in Argentina.
Officials are being given more power and resources to tackle the epidemic, and school holidays for millions of children are being extended.
Argentina has confirmed more than 1,500 cases of swine flu, which is spreading during the southern hemisphere winter.
Meanwhile, an international conference on swine flu is opening in Mexico.
Teams from some 40 countries are attending the three-day event in Cancun. The head of the World Health Organization, Margaret Chan, is also participating.
The health emergency measures in the capital and surrounding Buenos Aires province were unveiled on Tuesday.
Local officials said they wanted to improve co-ordination between different state services and to put more medical staff on stand-by.
They also said that school classes in the capital and three other regions would be cancelled from Monday, bringing forward winter holidays that had been due to start on 20 July.
"Families shouldn't treat this as extra holidays for the kids. They should see it as a time for the children to stay at home as much as possible and avoid places where people are crowded together," said Buenos Aires Mayor Mauricio Macri.
He also appealed for calm, saying that officials were doing everything possible to control the epidemic.
Officials said that restaurants, cinemas and other public buildings would remain open.
Much of Argentina's population lives in the capital and the province.
Many of the cases in the region have been reported in working class and poorer areas, says the BBC's Candace Piette in Buenos Aires.
There has been much criticism that the government may have responded too late to stop the epidemic, our correspondent says.
Argentina has had the third largest number of swine flu deaths in the world after Mexico and the United States.