Welcome again to JJNN for February 25th, 2009. Today I will be talking about influenza.
During this time of the year "influenza" is almost like a dirty word. No one ever wants to deal with getting influenza. Of course the easiest way to avoid getting influenza is to avoid anyone that even looks the least bit sick. Well, things like getting a flu shot and taking care of your self works as well, but who wants to go to all that work?
It turns out the Japanese National Institute of Infectious Diseases (NIID) is really worried about a new type of foreign strain of influenza virus making it's way into Japan. They set up models to to see how a new type of flu virus will spread in Tokyo and the areas around Tokyo if just one office worker brings back the virus from a foreign country. It is actually interesting how they came up with the model. It seems they took a sampling of 34,000,000 people that live in Tokyo and in all the prefectures that surround Tokyo. They tracked how these people get from place to place as well as where these people were during the day. From this data they were able to tell who would come into contact with who. In other words they can tell how many people come into contact with the person that is sick. If you assume that most of the people that come into contact with the virus will get sick (this is a good assumption because the Japanese people do not have antibodies for the new type of flu) than you can figure out how many people will get sick. Now here is the fun part. You have to take all those people and figure out how many people they meet and do the same thing as you did with the first person. As you can see, the numbers of people that get sick gets big real fast. This would be the start of an epidemic.
NIID ran many different simulations on their model to find the best way to reduce the number of people that might come down with the new flu virus. They found the best way deal with the problem was to make sure people don't walk around spreading the disease. The results are amazing. If no actions are taken 51.6% of all the people around Tokyo could come down with the flu. If all the schools (from pre-school to university) are closed down this only drops to 47.4%. That is not a very big drop. If all the schools are closed and 40% of the people that would normal go to work would stay home the number of people that will get sick goes down to 19.1%. And if the number of people staying home from work rises to 60% the number of that would get sick goes down to a nice 9.5%. It is worth mentioning that around 9% is the infection rate for the flu virus on a normal year in Japan. That is a lot of numbers but here it what it would look like visually.