California Department of Public Health, Richmond, California, United States of America.
PLoS One. 2011 Apr 5;6(4):e18221. doi: 10.1371/journal.pone.0018221.
While children and young adults had the highest attack rates due to 2009 pandemic (H1N1) influenza A (2009 H1N1), studies of hospitalized cases noted high fatality in older adults. We analyzed California public health surveillance data to better characterize the populations at risk for dying due to 2009 H1N1.
A case was an adult ≥20 years who died with influenza-like symptoms and laboratory results indicative of 2009 H1N1. Demographic and clinical data were abstracted from medical records using a standardized case report form. From April 3, 2009-August 10, 2010, 541 fatal cases ≥20 years with 2009 H1N1 were reported. Influenza fatality rates per 100,000 population were highest in persons 50-59 years (3.5; annualized rate = 2.6) and 60-69 years (2.3; annualized rate = 1.7) compared to younger and older age groups (0.4-1.9; annualized rates = 0.3-1.4). Of 486 cases hospitalized prior to death, 441 (91%) required intensive care unit (ICU) admission. ICU admission rates per 100,000 population were highest in adults 50-59 years (8.6). ICU case-fatality ratios among adults ranged from 24-42%, with the highest ratios in persons 70-79 years. A total of 425 (80%) cases had co-morbid conditions associated with severe seasonal influenza. The prevalence of most co-morbid conditions increased with increasing age, but obesity, pregnancy and obstructive sleep apnea decreased with age. Rapid testing was positive in 97 (35%) of 276 tested. Of 482 cases with available data, 384 (80%) received antiviral treatment, including 49 (15%) of 328 within 48 hours of symptom onset.
Adults aged 50-59 years had the highest fatality due to 2009 H1N1; older adults may have been spared due to pre-existing immunity. However, once infected and hospitalized in intensive care, case-fatality ratios were high for all adults, especially in those over 60 years. Vaccination of adults older than 50 years should be encouraged.
虽然儿童和青少年因 2009 年大流行（H1N1）流感 A （2009 H1N1）而发病率最高，但住院病例研究指出老年人死亡率较高。我们分析了加利福尼亚州公共卫生监测数据，以更好地描述因 2009 年 H1N1 而死亡的高危人群。
病例是指≥20 岁的成年人，其死于流感样症状且实验室结果表明存在 2009 年 H1N1。使用标准化病例报告表从病历中提取人口统计学和临床数据。从 2009 年 4 月 3 日至 2010 年 8 月 10 日，报告了 541 例≥20 岁的 2009 年 H1N1 死亡病例。每 100,000 人中有 50-59 岁（3.5；年化率为 2.6）和 60-69 岁（2.3；年化率为 1.7）的流感病死率最高，而年龄较小和较大的年龄组则为 0.4-1.9（年化率为 0.3-1.4）。在死亡前住院的 486 例中，有 441 例（91％）需要入住重症监护病房（ICU）。每 100,000 人中有 50-59 岁的 ICU 入院率最高（8.6）。成年人 ICU 病例的病死率在 24-42％之间，其中 70-79 岁的人最高。总共 425 例（80％）有与严重季节性流感相关的合并症。大多数合并症的患病率随年龄增长而增加，但肥胖，怀孕和阻塞性睡眠呼吸暂停症随年龄增长而减少。在 276 例接受检测的患者中，有 97 例（35％）的快速检测呈阳性。在 482 例有可用数据的病例中，有 384 例（80％）接受了抗病毒治疗，其中 49 例（15％）在症状出现后 48 小时内接受了治疗。
50-59 岁的成年人因 2009 年 H1N1 而死亡的比例最高；老年人可能由于先前存在的免疫力而幸免。但是，一旦感染并住院进入重症监护病房，所有成年人的病死率都很高，尤其是 60 岁以上的成年人。应鼓励对 50 岁以上的成年人进行疫苗接种。
