Epidemic Intelligence Service, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, United States of America.
PLoS One. 2011;6(12):e29301. doi: 10.1371/journal.pone.0029301. Epub 2011 Dec 20.
In 2009, a novel influenza virus (2009 pandemic influenza A (H1N1) virus (pH1N1)) caused significant disease in the United States. Most states, including Florida, experienced a large fall wave of disease from September through November, after which disease activity decreased substantially. We determined the prevalence of antibodies due to the pH1N1 virus in Florida after influenza activity had peaked and estimated the proportion of the population infected with pH1N1 virus during the pandemic.
During November-December 2009, we collected leftover serum from a blood bank, a pediatric children's hospital and a pediatric outpatient clinic in Tampa Bay Florida. Serum was tested for pH1N1 virus antibodies using the hemagglutination-inhibition (HI) assay. HI titers ≥40 were considered seropositive. We adjusted seroprevalence results to account for previously established HI assay specificity and sensitivity and employed a simple statistical model to estimate the proportion of seropositivity due to pH1N1 virus infection and vaccination.
During the study time period, the overall seroprevalence in Tampa Bay, Florida was 25%, increasing to 30% after adjusting for HI assay sensitivity and specificity. We estimated that 5.9% of the population had vaccine-induced seropositivity while 25% had seropositivity secondary to pH1N1 virus infection. The highest cumulative incidence of pH1N1 virus infection was among children aged 5-17 years (53%) and young adults aged 18-24 years (47%), while adults aged ≥50 years had the lowest cumulative incidence (11-13%) of pH1N1 virus infection.
After the peak of the fall wave of the pandemic, an estimated one quarter of the Tampa Bay population had been infected with the pH1N1 virus. Consistent with epidemiologic trends observed during the pandemic, the highest burdens of disease were among school-aged children and young adults.
2009 年，一种新型流感病毒（2009 年大流行性流感 A（H1N1）病毒（pH1N1））在美国引起了严重疾病。包括佛罗里达州在内的大多数州在 9 月至 11 月经历了一波秋季疾病高峰，此后疾病活动大幅减少。我们在流感活动达到高峰后确定了佛罗里达州 pH1N1 病毒抗体的流行率，并估计了大流行期间感染 pH1N1 病毒的人群比例。
在 2009 年 11 月至 12 月期间，我们从佛罗里达州坦帕湾的一家血库、一家儿科儿童医院和一家儿科门诊收集了剩余的血清。使用血凝抑制（HI）试验检测血清中 pH1N1 病毒抗体。HI 滴度≥40 被认为是血清阳性。我们调整了血清阳性率结果，以考虑到之前建立的 HI 试验特异性和敏感性，并采用简单的统计模型来估计由于 pH1N1 病毒感染和疫苗接种而导致的血清阳性率。
在研究期间，佛罗里达州坦帕湾的总体血清阳性率为 25%，调整 HI 试验敏感性和特异性后上升至 30%。我们估计，5.9%的人口具有疫苗诱导的血清阳性率，而 25%的人口具有 pH1N1 病毒感染引起的血清阳性率。pH1N1 病毒感染的最高累积发病率是 5-17 岁的儿童（53%）和 18-24 岁的年轻成年人（47%），而≥50 岁的成年人感染 pH1N1 病毒的累积发病率最低（11-13%）。
在秋季疫情高峰过后，估计坦帕湾有四分之一的人口感染了 pH1N1 病毒。与大流行期间观察到的流行病学趋势一致，疾病负担最高的是学龄儿童和年轻成年人。
