A North American map tracking the swine flu the provided by Google.

Source: The New York Times

The new swine flu cases are caused by an influenza strain called H1N1, which appears to be easily passed from person to person. Mexican health authorities have confirmed 149 deaths from that flu and are investigating the illnesses of 1,600 people, and the United States, Canada, Spain and other countries have confirmed or are investigating cases.

But doctors have little information yet on the mortality rate, as there is no reliable data on the total number of people infected. Reports from the United States suggest that some cases may be mild and therefore may go undetected — allowing the disease to spread further. Flu experts are trying to determine if this year’s flu shots, which contain H1N1 strain, offer any protection.

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