A recent reading of Google Flu trends for Canada suggests that flu activity is in decline after a huge spike in October.

Using data current through November 9th, Google Flu trends shows that flu activity is still intense in every province except Quebec, but is off its peak.

The following chart shows the most recent reading from Google Flu trends which shows activity having peaked in the last week, with intense activity still occurring across the country except in Quebec.

While the bulk of Canada is still reporting intense flu activity, the U.S. is reporting mostly high activity with more intense activity in the North Eastern states (see chart below). The trend which suggests flu activity has peaked is also evident in the American numbers.

About Google Flu Trends

In its research, search giant Google has found that certain flu-related search terms appear to be excellent indicators of flu activity and last year created a site for Americans called Google Flu Trends. In October, the company announced that Flu Trends had been expanded to 16 additional countries including Canada.

The Google Flu trends website came about after a small team of Google software engineers began to explore if the company could go beyond simple trends and accurately model real-world phenomena using patterns in search queries.

In 2007, after meeting with the public health gurus on Google.org's Predict and Prevent team, the team decided to focus on outbreaks of infectious disease, which are responsible for millions of deaths around the world each year. One such disease: influenza, commonly known as "the flu," is responsible for up to 500,000 deaths worldwide each year, primarily among the elderly and immune compromised individuals.

In simple terms, more people queried Google on flu-related terms when they started getting the flu. Based on this discovery, Google launched Google Flu Trends, where you can find up-to-date influenza-related activity estimates for each of the 50 states in the U.S.

The reason Google's data was so fascinating for scientists is that traditional flu surveillance systems take 1-2 weeks to collect and release surveillance data, but Google search queries can be automatically counted very quickly. By making flu estimates available each day, Google believes its Flu Trends may provide an early-warning system for outbreaks of influenza.

So how good was Flu trends in its first year?

The good news is the company says analysis of the 2007 season shows that Flu Trends had a close 0.92 correlation with official U.S. flu data.

How Google Flu Trends works

The following is an explanation of how Google Flu Trends works, narrated by product manager, Dr. Roni Zeiger that discusses how Google built its model.