# 2829
From the Asahi Shimbun today we get this story about a study conducted by Japan's National Institute of Infectious Diseases that looked at the interventions that would be needed in order to reduce the impact of a pandemic.
Out of a population of roughly 34 million (just in Tokyo), they theorize half could become infected with a novel pandemic strain if no efforts were made to reduce human contact.
This attack rate of 50% is almost twice what most countries have envisioned, although the UK has recently spoken about numbers in that range.
The higher the attack rate, the greater of an impact a pandemic would have on society, health care providers, and the economy. And of course, the greater the human toll as well.
By closing all schools, and reducing commuter traffic by 40%, they believe they can reduce the attack rate to a more manageable 25%.
First today's article, then a quick flashback to December 2008.
A hat tip to Carol@SC on the Flu Wiki for posting this story.
New flu could infect 17 million in Tokyo area
BY HISASHI HATTORI, THE ASAHI SHIMBUN
2009/2/25
More than half the population of the Tokyo metropolitan area could contract a new strain of influenza if nothing is done after one carrier brings the virus to the capital, according to a study.
The study by the National Institute of Infectious Diseases calls for all schools to close and 40 percent of commuters to stay at home to keep the infection rate at 25 percent or lower, the level the central government envisions in dealing with new strains of influenza.
"The key to preventing the spread of infection is the degree of measures to restrict people from going out," said Yasushi Ohkusa, a senior research scientist at the institute who took part in the study.
The scenario of the institute is based on data from a council on traffic planning in the Tokyo metropolitan area.
The council tracked down how 34 million people in Tokyo and Kanagawa, Saitama and Chiba prefectures, as well as southern Ibaraki Prefecture, move and where they are during the day.
The institute came up with a scenario in which a company employee is infected with a new strain of flu while overseas and returns home to Hachioji, Tokyo, on the third day of infection. The employee develops symptoms after reporting to work in Tokyo's Marunouchi district on the fourth day.
After a hospital diagnoses the employee with a new type of flu, local governments start taking action on the seventh day.
The spread of the flu will reach its peak around the 25th day, according to the scenario.
The study predicts that 51.6 percent of residents in the Tokyo metropolitan area will contract the flu if no measures are taken.
If all schools are closed and the number of commuters is reduced by 40 percent after local governments ask residents to stay home, the infection rate will fall to 19.1 percent, the study predicted.
The institute says that if the number of commuters is further reduced by 60 percent, the infection rate will be lowered to 9.5 percent, the same level as that of regular, seasonal influenza.(IHT/Asahi: February 25,2009)
Last December I ran a blog about a Japanese study conducted on commuter trains, to determine what carrying capacity they could maintain during a pandemic and still allow for reasonable social distancing.
The verdict was that they could carry only 20% of their usual traffic, which is a far cry from the 60% envisioned by today's report. See Japan: Social Distancing Test On Commuter Trains for more details.
Here is just a snippet from one of the articles.
Flu epidemic measures tested on train riders
Kyodo News
A research institute for the transport ministry conducted a test Monday on how far apart passengers should be while riding on commuter trains in the event of a new type of influenza outbreak.
Safe distance: In a test of passenger control steps to be taken during a possible flu epidemic, officials from a labor ministry research institute measure the distance between mask-wearing subjects in Adachi Ward, Tokyo, on Monday. KYODO PHOTO
According to the Policy Research Institute for the Land, Infrastructure, Transport and Tourism Ministry, passengers would be required to keep a distance of 1 to 2 meters to prevent the infection spreading by coughs or sneezes.
Mega cities such as Tokyo or New York, where millions of people rub shoulders every day, are more likely to see high attack rates than say, Springfield, Missouri or Keokuk, Iowa.
The more close contacts a person has, the more likely they are to either contract, or pass on, the virus.
Mitigation efforts, such as closing schools and limiting the number of people allowed on commuter trains, ought to reduce the transmission of the virus.
They do come with a price, both socially and economically.
But then, so would a 50% attack rate.
The logistics of deciding who gets priority for public transit, controlling the boarding onto the trains, and dealing with the economic outfall from employee absenteeism are sizable.
Which is why its is a good thing they are looking into the feasibility of this now, instead of waiting until a pandemic begins.
