医師の一分

アクセスカウンタ

zoom RSS 季節性インフルエンザ死亡数推計値の引き下げ/米国 CDC インフルエンザ

<<   作成日時 : 2010/08/31 20:24   >>

なるほど(納得、参考になった、ヘー) ブログ気持玉 1 / トラックバック 0 / コメント 0

 CDCは木曜日に、季節性インフルエンザでの推計死亡者数を36,000人から24,000人に引き下げた。以前の推計は高齢者の死亡率が高いH3N2インフルエンザが流行していた1990-1999年の研究によるものであったという。新たな推計は1976-2007年のデータの再評価による。インフルエンザによる死亡者数は、1986-87年の3,349人から、2003-04年の48,614人まで大きく変動がある。
 2009年のブタインフルエンザ流行は新種のため影響は受けない。3月に約12,000人、90%が6才未満の死亡で予想より少なかった。
 CDCによれば、報道機関は36,000人・24,000人のような数値ではなく数万人と言ったもう少し漠然とした数値を使うべきであると言うが、36,000人が季節性インフルエンザで死亡していると繰り返し言ってきたのはCDCである。

----------------------------------------------------
Estimate Lowered of Typical Flu Toll
By THE NEW YORK TIMES
Published: August 26, 2010
http://www.nytimes.com/2010/08/27/health/27flu.html

The Centers for Disease Control and Prevention on Thursday substantially lowered its often-quoted estimate of how many people die in a typical flu season, to 24,000 from 36,000.

The previous estimate, the agency said, was based on a study of the years 1990 to 1999, during which the H3N2 strain of flu predominated, and H3N2 is far more deadly to the elderly than the other two common seasonal strains, H1N1 and B.

The new estimate is based on a re-evaluation of the years 1976 to 2007. Deaths attributed to flu fluctuated widely, from a low of 3,349 in the winter of 1986-7 to a high of 48,614 in 2003-4.

Neither estimate is affected by the 2009 swine flu pandemic, which was caused by a new variant of the H1N1 strain. In March, the centers estimated that about 12,000 people died of that strain ― far fewer than expected ― although 90 percent of them were under 65, while seasonal flu normally kills elderly people.

In presenting the new numbers on Thursday, the centers urged journalists to stop using annual averages like 36,000 or 24,000 and to use more vague estimates like “tens of thousands of people may die.” However, during news conferences last year relating to swine flu, top C.D.C. officials repeatedly said that 36,000 people die in a typical flu season.

-------------------------------------------------
Estimates of Deaths Associated with Seasonal Influenza --- United States, 1976--2007

Weekly
August 27, 2010 / 59(33);1057-1062

画像Influenza infections are associated with thousands of deaths every year in the United States, with the majority of deaths from seasonal influenza occurring among adults aged ≥65 years (1--4). For several decades, CDC has made annual estimates of influenza-associated deaths, which have been used in influenza research and to develop influenza control and prevention policy. To update previously published estimates of the numbers and rates of influenza-associated deaths during 1976--2003 by adding four influenza seasons through 2006--07, CDC used statistical models with data from death certificate reports. National mortality data for two categories of underlying cause of death codes, pneumonia and influenza causes and respiratory and circulatory causes, were used in regression models to estimate lower and upper bounds for the number of influenza-associated deaths. Estimates by seasonal influenza virus type and subtype were examined to determine any association between virus type and subtype and the number of deaths in a season. This report summarizes the results of these analyses, which found that, during 1976--2007, estimates of annual influenza-associated deaths from respiratory and circulatory causes (including pneumonia and influenza causes) ranged from 3,349 in 1986--87 to 48,614 in 2003--04. The annual rate of influenza-associated death in the United States overall during this period ranged from 1.4 to 16.7 deaths per 100,000 persons. The findings also indicated the wide variation in the estimated number of deaths from season to season was closely related to the particular influenza virus types and subtypes in circulation.

The current study extends estimates of influenza-associated deaths from two previous CDC studies (2,3) by adding data from four more influenza seasons for a total of 31 influenza seasons (1976--2007). Estimates are provided for three age groups (<19 years, 19--64 years, and ≥65 years) and for two categories of underlying cause of death codes: 1) pneumonia and influenza causes and 2) respiratory and circulatory causes. Deaths from pneumonia and influenza causes are highly correlated with the circulation of influenza (1) and can be considered a lower bound for deaths associated with influenza (2,4). However, a diagnosis of influenza virus infection often is not confirmed with sensitive and specific laboratory diagnostics, particularly among older persons, and even when identified is rarely recorded on death certificates (5). Many deaths associated with influenza infections occur from secondary infections such as bacterial pneumonia or complications of chronic conditions such as congestive heart failure and chronic obstructive pulmonary disease (6). Therefore, estimates using underlying respiratory and circulatory mortality data (which include pneumonia and influenza causes) can provide an upper bound for influenza-associated deaths (2,7).

Using methods published previously (2,3), CDC estimated the numbers and rates of influenza-associated deaths by virus type and subtype by using Poisson regression models that incorporated weekly national respiratory viral surveillance data. Weekly influenza test results by virus type and subtype were provided by approximately 80 World Health Organization (WHO) and 70 National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories in the United States (8). Prominent influenza type and subtype were defined as at least 20% of all isolates that were tested in that season. Mortality data were obtained from the National Vital Statistics System and reflect the underlying cause of death recorded on death certificates (9). Deaths were categorized using the International Classification of Diseases eighth revision (ICD-8), ninth revision (ICD-9), or 10th revision (ICD-10), as appropriate. Weekly estimates of the U.S. population by age group were used as part of the model to correspond to the weekly viral surveillance estimates. All data for deaths with underlying pneumonia and influenza causes and respiratory and circulatory causes were actual counts based on the death certificate ICD codes. To estimate the proportion of deaths that were influenza associated, the average annual number of deaths estimated by the model was divided by the average annual counts of death with underlying pneumonia and influenza causes and respiratory and circulatory causes.

For deaths with underlying pneumonia and influenza causes during 1976--2007 in the United States, the models estimated an annual overall average of 6,309 (range: 961 in 1986--87 to 14,715 in 2003--04) influenza-associated deaths (Table 1). For these underlying causes, the average annual rate of influenza-associated death was 2.4 deaths per 100,000 (range: 0.4--5.1).

Among persons aged <19 years, an estimated annual average of 97 (range: 41 in 1981--82 to 234 in 1977--78) influenza-associated deaths with underlying pneumonia and influenza causes occurred (Table 1). The average annual rate of influenza-associated deaths for this age group was 0.1 deaths per 100,000 persons (range: 0.1--0.3). Among adults aged 19--64 years, an estimated annual average of 666 (range: 173 in 1981--82 to 1,459 in 2004--05) influenza-associated deaths with underlying pneumonia and influenza causes occurred. The average annual rate of influenza-associated deaths for this age group was 0.4 deaths per 100,000 persons (range: 0.1--0.8). Among adults aged ≥65 years, an estimated annual average of 5,546 (range: 673 in 1978--79 to 13,245 in 2003--04) influenza-associated deaths with underlying pneumonia and influenza causes occurred. The average annual rate of influenza-associated deaths for this age group was 17.0 deaths per 100,000 (range: 2.4--36.7). Deaths among persons aged ≥65 years accounted for 87.9% of the overall estimated average annual influenza-associated deaths with underlying pneumonia and influenza causes.

For deaths with underlying respiratory and circulatory causes (including pneumonia and influenza causes) during 1976--2007, the models estimated an annual U.S. average overall of 23,607 (range: 3,349 in 1986--87 to 48,614 in 2003--04) influenza-associated deaths (Table 2). For these underlying causes, the average annual rate of influenza-associated death was 9.0 deaths per 100,000 (range: 1.4--16.7).

Among persons aged <19 years, an estimated annual average of 124 (range: 57 in 1981--82 to 197 in 1977--78) influenza-associated deaths with underlying respiratory and circulatory causes occurred (Table 2). The average annual rate of influenza-associated deaths for this age group was 0.2 deaths per 100,000 persons (range: 0.1--0.3). Among adults aged 19--64 years, an estimated annual average of 2,385 (range: 504 in 1981--82 to 4,752 in 2003--04) influenza-associated deaths with underlying respiratory and circulatory causes occurred. The average annual rate of influenza-associated deaths for this age group was 1.5 deaths per 100,000 persons (range: 0.4--3.1). Among adults aged ≥65 years, an estimated annual average of 21,098 (range: 2,344 in 1986--87 to 43,727 in 2003--04) influenza-associated deaths with underlying respiratory and circulatory causes occurred. The average annual rate of influenza-associated deaths for this age group was 66.1 deaths per 100,000 (range: 8.0--121.1). Deaths among persons aged ≥65 years accounted for 89.4% of the overall estimated average annual influenza-associated deaths with underlying respiratory and circulatory causes.

For both causes, the average mortality rates for the 22 seasons during which influenza A(H3N2) was a prominent strain were 2.7 times higher than for the nine seasons that it was not. The average annual number of influenza-associated deaths during influenza A(H3N2) prominent seasons was 7,722 for pneumonia and influenza causes and 28,909 for respiratory and circulatory causes, compared with 2,856 deaths for pneumonia and influenza causes and 10,648 deaths for respiratory and circulatory causes in seasons in which it was not.

The distribution of mortality across age groups was similar for the two groups of coded deaths. For pneumonia and influenza causes, the proportions of average deaths overall were 1.5%, 10.6%, and 87.9% for persons aged <19 years, 19--64 years, and ≥65 years, respectively. For respiratory and circulatory causes, the proportions were 0.5%, 10.1%, and 89.4%.

Based on an average annual count of 74,363 for all pneumonia and influenza deaths, and an average annual estimate of 6,309 deaths associated with influenza in this category, 8.5% of all pneumonia and influenza deaths were influenza associated. Based on an annual average count of 1,132,319 for all respiratory and circulatory deaths and an average annual estimate of 23,607 deaths associated with influenza in this category, 2.1% of all respiratory and circulatory deaths were influenza associated.
Reported by

MG Thompson, PhD, DK Shay, MD, H Zhou, MSc, MPH, CB Bridges, MD, PY Cheng, PhD, E Burns, MA, JS Bresee, MD, NJ Cox, PhD, Influenza Div, National Center for Immunization and Respiratory Diseases, CDC.

テーマ

関連テーマ 一覧


月別リンク

ブログ気持玉

クリックして気持ちを伝えよう!
ログインしてクリックすれば、自分のブログへのリンクが付きます。
→ログインへ
気持玉数 : 1
なるほど(納得、参考になった、ヘー)

トラックバック(0件)

タイトル (本文) ブログ名/日時

トラックバック用URL help


自分のブログにトラックバック記事作成(会員用) help

タイトル
本 文

コメント(0件)

内 容 ニックネーム/日時

コメントする help

ニックネーム
本 文
季節性インフルエンザ死亡数推計値の引き下げ/米国 CDC インフルエンザ 医師の一分/BIGLOBEウェブリブログ
文字サイズ:       閉じる