Coordinación de Vigilancia Epidemiológica y Apoyo en Contingencias, Instituto Mexicano del Seguro Social, Mexico, DF, Mexico.
Arch Med Res. 2012 Oct;43(7):563-70. doi: 10.1016/j.arcmed.2012.09.005. Epub 2012 Oct 16.
A substantial recrudescent wave of pandemic influenza A/H1N1 affected the Mexican population from December 1, 2011-March 20, 2012 following a 2-year period of sporadic transmission.
We analyzed demographic and geographic data on all hospitalizations with severe acute respiratory infection (SARI) and laboratory-confirmed A/H1N1 influenza, and inpatient deaths, from a large prospective surveillance system maintained by a Mexican social security medical system during April 1, 2009-March 20, 2012. We also estimated the reproduction number (R) based on the growth rate of the daily case incidence by date of symptoms onset.
A total of 7569 SARI hospitalizations and 443 in-patient deaths (5.9%) were reported between December 1, 2011, and March 20, 2012 (1115 A/H1N1-positive inpatients and 154 A/H1N1-positive deaths). The proportion of laboratory-confirmed A/H1N1 hospitalizations and deaths was higher among subjects ≥60 years of age (χ(2) test, p <0.0001) and lower among younger age groups (χ(2) test, p <0.04) for the 2011-2012 pandemic wave compared to the earlier waves in 2009. The reproduction number of the winter 2011-2012 wave in central Mexico was estimated at 1.2-1.3, similar to that reported for the fall 2009 wave, but lower than that of spring 2009.
We documented a substantial increase in the number of SARI hospitalizations during the period December 2011-March 2012 and an older age distribution of laboratory-confirmed A/H1N1 influenza hospitalizations and deaths relative to 2009 A/H1N1 pandemic patterns. The gradual change in the age distribution of A/H1N1 infections in the post-pandemic period is consistent with a build-up of immunity among younger populations.
2011 年 12 月 1 日至 2012 年 3 月 20 日，甲型 H1N1 流感大流行在墨西哥出现了大量的复发性浪潮，此前经历了两年的零星传播。
我们分析了墨西哥社会保障医疗系统维持的大型前瞻性监测系统中所有严重急性呼吸道感染（SARI）和实验室确诊的甲型 H1N1 流感住院病例以及住院患者死亡病例的人口统计学和地理数据，时间为 2009 年 4 月 1 日至 2012 年 3 月 20 日。我们还根据症状出现日期的每日病例发病率增长率估计了繁殖数（R）。
2011 年 12 月 1 日至 2012 年 3 月 20 日期间，共报告了 7569 例 SARI 住院和 443 例住院死亡病例（1115 例甲型 H1N1 阳性住院患者和 154 例甲型 H1N1 阳性死亡病例）。与 2009 年的早期流行波相比，年龄≥60 岁的患者实验室确诊的甲型 H1N1 住院和死亡比例更高（卡方检验，p<0.0001），而年龄较小的年龄组则更低（卡方检验，p<0.04）。墨西哥中部冬季 2011-2012 年流行波的繁殖数估计为 1.2-1.3，与秋季 2009 年流行波相似，但低于春季 2009 年流行波。
我们记录了 2011 年 12 月至 2012 年 3 月期间 SARI 住院人数的大幅增加，以及与 2009 年甲型 H1N1 大流行模式相比，实验室确诊的甲型 H1N1 流感住院和死亡病例的年龄分布更为年长。甲型 H1N1 感染在大流行后期年龄分布的逐渐变化与年轻人群中免疫力的建立一致。
