A New Type Influenza (Pandemic H1N1 2009)-Its Onset and Progress till Now-

A large-scale epidemic of influenza exceeding the ordinary one developed 3 times in the last century. During 40 years following the appearance of Hong Kong influenza virus in 1968, mankind has not been attacked by an unusual epidemic of influenza. Recently, various measures against a world-wide spread of pandemic influenza due to a new type influenza virus have been progressed over the world by a great concern of people. The basic measures against the pandemic are to delay an appearance of the new type virus as possible. It is important to delay the spread of disease if the virus appeared and minimize health damage and social disorder as possible if expanded. Those countermeasures should include not only medical and health care measures but also hygienic ones. In addition, it is important to elicit social understanding and effectively coordinate them. These measures are applicable to an outbreak of not only the new type influenza but also newly appearing infectious diseases as well as previous ones, resulting in strengthening of the whole measures against infectious diseases.<BR>Under these circumferences, a new type influenza virus that was the first-experienced virus for human appeared in Mexico and it was named as “new influenza virus”. This virus originated in North America spread to Europe and all over the world including Asia and the southern hemisphere. In our country, the new influenza virus was detected for the first at Narita Airport Quarantine Station on May 9, 2009 and its confirmed cases were also found at Kobe city on May 16 and at Osaka city on May 17. Then, group infections developed in senior high schools in Hyogo and Osaka prefectures and various countermeasures such as school closures in local communities and waiting at home of people who had close contact with infected persons were taken, resulting that the spread of new type influenza to the general public was fairly repressed in the two prefectures. However, development of the new influenza virus succeeded in various parts of Japan since middle June. In August, the onset of influenza-like diseases became similar to that in December of an average year. In October to November, the status of its infection became similar to that in an average winter and this outbreak was barely controlled in December. In the forth week of 2010, the cumulative number of influenza patients was estimated at more than 20 million. This was larger than the cumulative patient number of 18 million in the season of influenza in 2004/2005, which was the peak for the previous nine seasons. The peak number of patients in 2010 ranked the third among the outbreaks of seasonal type influenza in previous nine years. The period of epidemic was 29 weeks, which was longer than that of seasonal influenza.<BR>The most important measures for the onset of new type influenza (pandemic) are to delay the invasion of epidemic as possible and once it invaded, it is necessary to prevent its rapid spread and lower the peak number of patients. As the results, the termination of epidemic might be postponed, but at present when the epidemic cooled down, it was thought that our original attempts were almost achieved.<BR>Among the patients infected with new influenza virus, some developed severe pneumonia, acute encephalopathy and fatal cases were found. Although there are not a few cases not reported to the Ministry, among 21 million patients (at the week-13 in 2010) in our country, which was reported as the cumulative number of patients till the day of Mar.23, 2010 to the Ministry of Health, Labour and Welfare, the number of death was 198, which was extremely smaller than those reported in various foreign countries. In our country, the mortality rate of new type influenza was 0.15 for 100,000 patients.<BR>(View PDF for the rest of the abstract.)