世界卫生组织称：甲型HIN1流感的传染性比季节性流感强

May 11, 2009 (CIDRAP News) – The World Health Organization (WHO) today said the novel H1N1 influenza (swine flu) virus seems to be more contagious than seasonal flu, but it generally causes "very mild illness" in otherwise healthy people.

2009年5月11日CIDRAP注消息 - 世界卫生组织(WHO)今天称，新的甲型H1N1流感（原称猪流感）病毒似乎比季节性流感的传染性更强，然而在健康人群中通常只会产生“非常轻的症状”。

"H1N1 appears to be more contagious than seasonal influenza," the WHO said in an online statement released today. "The secondary attack rate of seasonal influenza ranges from 5% to 15%. Current estimates of the secondary attack rate of H1N1 range from 22% to 33%." (The secondary attack rate is defined as the frequency of new cases of a disease among the contacts of known cases.)

今天，WHO在一个在线声明中指出，“H1N1看起来比季节性流感的传染性更强，季节性流感的二代发病率为5%~15%，而目前对H1N1的二代发病率的估计在22%~33%之间（二代发病率指与确诊病例直接接触产生新病例的发生率）。

The agency noted that, because the virus is new, scientists expect that few people are likely to have any immunity to it. In that context, the statement that the new virus is more contagious than seasonal flu is not surprising, but it appears to be the first time the WHO has offered any specific figures comparing the contagiousness of the novel virus and seasonal flu.

我们注意到，由于病毒是新型的，科学家预期很少会有人有免疫力。在这种情况下，预期新病毒比季节性流感的传染性更强并不奇怪，但这似乎是WHO第一次用具体的数字对新病毒的传染性和季节性流感作比较。

The WHO further stated, "With the exception of the outbreak in Mexico, which is still not fully understood, the H1N1 virus tends to cause very mild illness in otherwise healthy people. Outside Mexico, nearly all cases of illness, and all deaths, have been detected in people with underlying chronic conditions."

WHO还进一步指出，“虽然对墨西哥的流感暴发仍未彻底查清，但除了墨西哥的爆发， H1N1病毒在健康人群中多数只产生极轻的病症，在墨西哥以外的国家，几乎所有发病病例，和所有的死亡病例，都发生在有潜在慢性病的人群中”。

The statement also noted that the outbreaks in Mexico and the United States have affected younger people more than seasonal flu typically does: "Though cases have been confirmed in all age groups, from infants to the elderly, the youth of patients with severe or lethal infections is a striking feature of these early outbreaks."

声明中还指出，在墨西哥和美国，H1N1比季节性流感会更容易传染给年轻人：“虽然所有年龄组，即从婴儿到老年都有发病，但青壮年病人重症和死亡比例高的确是这次流感暴发早期的一个显著特征”。

Pandemic phases versus severity

流感暴发的警戒等级严重程度之间的关系
Much of today's WHO statement, titled "Assessing the severity of an influenza pandemic," explained the numerous variables that affect the severity of a pandemic. It was released the same day that Dr. Keiji Fukuda, speaking at a press briefing, took pains to explain that the WHO's pandemic alert phases do not describe the severity of an outbreak but refer only to how widely the disease has spread.

在WHO今天发表的题为“对流感暴发严重程度的评估”中，主要篇幅都在对影响流感严重程度的各种因素进行说明。在声明发布的同日，在对记者的一个情况介绍中，Keiji Fukuda博士尽力解释了WHO的流感警戒等级并不说明流感暴发严重程度，只说明疾病传播广度的原因。

"In the past few weeks we've been asked, is this a mild event? The response is that we are not sure right now. The situation is evolving," said Fukuda, the WHO's assistant director-general for health security and environment.

“在过去的几个星期，人们一直在问我们，此次暴发是否只是一次温和的暴发？我们的答复是，现在还不确定，局势还在变化中”，WHO负责卫生安全和环境的署长助理Keiji Fukuda博士说。

Phase 5, which the WHO declared on Apr 29, means that sustained community transmission is occurring in more than one country in one global region. Phase 6 means a full-scale pandemic, with community transmission going on in more than one region. The WHO says that has not happened yet: While countries such as Spain and the United Kingdom have dozens of cases, they have been limited to school and institutional settings and have not escaped into the wider community.

WHO 4月29日将流感暴发的警戒等级提高到5级，这意味着，在全球范围内，不止有一个国家发生了持续性的人际传播，而6级则意味着在一个地区以上正在发生全面的、大范围的人际传播。WHO认为，这个情况还未发生：尽管西班牙和英国已经分别有几十个病例，但仍然只限于学校和一些机构设施内，尚未扩散到更广的人群范围。

"Now severity is a different characteristic," Fukuda said. The severity of an epidemic can refer to the incidence of mild, moderate, or severe illness, and it can also refer to the overall social and economic impact of an outbreak on a country, he said.

“而流感暴发的严重程度有其不同的特点”，Fukuda博士说，流感爆发的严重程度不仅和发病的轻重相关，而且还会和它对一个国家的社会、经济的总体影响相关。

The WHO statement goes into more detail. It says the virulence of the virus largely determines the number of severe illnesses and deaths, but many other factors influence the overall severity, including the contagiousness of the virus, the age distribution of cases, the prevalence of chronic health problems and malnutrition in a population, viral mutations, the number of waves of illness, and the quality of health services.

WHO在声明中进一步解释，病毒的毒性主要会决定重症和死亡病例的数量，但影响流感暴发严重程度的还有其他的因素，包括病毒的接触传染性、发病的年龄分布特点、是否更会在慢性病和营养不良人群中流行、病毒的变异性、暴发期的次数和医疗服务的质量等。

Although WHO officials have been careful not to characterize the severity of the H1N1 situation, the agency is working on a system to help provide that kind of information, Fukuda said.

Fukuda博士说，尽管WHO的官员一直都小心地避免对H1N1流感的严重程度进行刻画，但WHO正通过一套系统帮助提供这方面的信息。

A reporter asked him if the WHO could come up with something like the US government's "Pandemic Severity Index," which was inspired by hurricane classifications. The reporter said the public is confused because the world is in phase 5 with a "mild" virus, in the context of pandemic preparations triggered by the often-lethal H5N1 avian flu virus.

一位记者询问，美国政府受飓风分级的启发，发布了“流感暴发严重程度指数”，WHO是否也会有类似的一个指标。那位记者说，公众现在都非常困惑，因为一个“温和”的病毒，现在全世界把警戒等级拉升到了5级的状态，而这种应对流感的准备是为应付致命的H5N1禽流感病毒而建立的。

Fukuda replied, "WHO, with the same group of people who have been working on phases and on pandemic preparedness plans, has been working on developing a way to grade severity. We have refrained at this point as to posting whether we think it's a mild stage or medium or severe. I think we will be trying to provide this guidance as soon as we can."

Fukuda博士答复说，“那些为流感暴发准备计划和警戒等级工作的WHO人员也正在努力建立一套方法来评价爆发的严重程度，但目前为止，在这个问题上我们一直都避免评价这场流感暴发是温和的，或是中等的，还是很严重的。我想我们会尽力，尽早给公众一个导则。”

He said that providing severity information has been "an active part of the pandemic preparedness thinking" in recent years, but he gave no details about what kind of system the WHO might come up with or when it would be unveiled.

他指出，提供严重程度的信息，近些年一直是“流感应对思考的一个积极的部分”，但他没有更详细地介绍WHO正在利用什么系统得出，或何时能够得出建议。

The US Department of Health and Human Services (HHS) announced its Pandemic Severity Index in February 2007 as part of its guidance on community interventions for combating a pandemic. The index is based on case-fatality rates (CFRs), with a CFR of 2% or greater signaling the most severe pandemic: category 5. The pandemics of 1957 and 1968 qualify as category 2 events, with CFRs between 0.1% and 0.5%, HHS officials said.

美国卫生和人类服务部(HHS)在2007年2月发布了“流感严重程度指数”，用以指导公众采取相应措施抗击流感。这个指数以病死率(CRSs)为依据，当CRS达到或超过2%时，就说明流感达到了最危险的程度：5级。HHS的官员讲，1957年和1968年的两次流感CRS分别达到了0.1%和0.5%，都属于2级事件。

Defining community spread

定义公众传播性
In other comments today, Fukuda said the criterion for "community spread" of a disease is "when you begin to see people who are getting infected and you're just not clear where they're getting infected from." He added that many US cases can't be traced anywhere, unlike the cases in school and institutional outbreaks.

作为今天另一个评论的要点，Fukuda博士说，评价一个疾病的“公众传播性”的标准是，“你开始看到有人被传染，而你却不清楚他们是从哪里被传染的时候”。他还指出，在美国的许多病例就无法追朔，不同于学校和机构设施内的爆发。

But in response to questions, he said there is no specific number of cases that signals community spread. "What you're really looking for is something that's convincing. . . not something that's just a quirk or an oddity," he said. "We're very mindful that going from phase 5 to phase 6 is a very important step and it really would be interpreted that way. I can't tell you whether that's 10 people or 100 people or so on."

但就这个问题，Fukuda博士说，目前能提示具有公众传播性的病例数量还不够明显，他说，“你所需要寻找的是那些有说服力的证据，而不应该只是让人感觉奇怪或异样，把警戒等级从5提高到6是非常重要的一个步骤，那的确需要有说服力的证据，对此我们是非常谨慎的，我不能告诉你，因为有10个人或是100个人无法追朔，等等，就把这作为提高警戒等级的根据。”

译者注：CIDRAP是Center for Infectious Disease Research & Policy(传染病研究与政策中心)的缩写，本资料来源：http://www.cidrapforum.com/cidrap/content/influenza/swineflu/news/may1109severity.html