Facebook becomes the latest social-networking site to monitor the spread of swine flu, tracking the occurrence of flu-related words and phrases in the United States and in Europe.

Meanwhile, Google has created a Google Flu Trends site to track the spread of swine flu through Mexico. Google, Twitter, Wikipedia and other Web 2.0 sites are now offering real-time information about the possible spread of the flu, although some critics assert that social-networking has the potential to spread unnecessary panic among the public.

Google Flu Trends, which was first released in the United States, in November, tries to track the incidence of flu based on the amount of searches for keywords related to influenza. The company called its Flu Trends for Mexico experimental because unlike in the United States, it does not have historical surveillance data to validate that its search data correlates to actual infections.

While the overall flu activity for Mexico is low, certain areas such as Oaxaca have been displaying moderate amounts of flu-related search activity.

In response to recent inquiries from public health officials, we've been attempting to use Google search activity in Mexico to help track human swine flu levels, Jeremy Ginsberg and Matt Mohebbi, software engineers for Google, wrote on the Google Blog on Thursday.

Experimental Flu Trends for Mexico is, as you might have guessed, very experimental. But the system has detected increases in flu-related searches in Mexico City (Distrito Federal) and a few other Mexican states in recent days.