The World Health Organization (WHO) and the Argentine health authorities expressed their concern from the beginning of the outbreak, that the imminent arrival of the southern winter could cause "more serious" effects in the southern hemisphere than those caused in Mexico,[2][3] and could lead to a rebound of the epidemic around the world.

[4] The first infection was confirmed on May 7 in a man who had come from Mexico City and had entered the country without symptoms on April 24.

Towards the end of May infection started in some schools in the northern community of the City of Buenos Aires and its suburbs, the main part of the country affected by the epidemic.

[5] In the second half of June, coinciding with the onset of winter, the virus was widely transmitted in Buenos Aires and spread to other parts of the country, especially the Province of Santa Fe, with its center in the city of Rosario.

On June 29, the Government decided to close schools throughout the month of July, a measure which affected 11 million students.

The measures taken by the authorities were primarily targeted to limit contagion during the winter months until the start of spring.

[9] In Argentina, seasonal flu outbreaks kill about 4,000 people each year, equivalent to a rate of 10 deaths per 100,000 inhabitants.

[11] April 26: The Ministry of Health issued an Epidemic Alert order asking airlines to report passengers with influenza symptoms arriving from Mexico and United States.

The government also stepped up safety checks, and thermal scanners were used in airports to detect passengers running fevers.

[16] June 28: Due to the ongoing legislative elections and the possible resignation of the Health Minister, Graciela Ocaña, reports of confirmed cases and deaths were suspended.

[17] July 2: The newly appointed Health Minister Juan Luis Manzur estimated the number of affected people to be as high as 100,000, as well as 44 confirmed deaths.

July 28: Impact on health services diminished significantly according to various specialists, though the death toll continued to increase, partly because of the delay in confirming previous fatalities.

[21] August 5: A new report was released by the ministry of health,[22] showing 762,711 ILI cases up to Aug 1, 2009, of which more than 700,000 were of the A (H1N1) swine flu type.