NEJM:年轻人可能更易感甲型H1N1流感

2009-05-11 admin 科学网
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美国H1N1流感感染者大部分是年轻人。

(图片来源:Pasieka / Science Photo Library)

美国科学家近日完成对美国境内最初的642名H1N1型流感确诊患者的分析,分析结果揭示了该病毒的分布状况、不同年龄段人群的易感性差别以及患病症状。相关研究报告发表在《新英格兰医学杂志》(The New England Journal of Medicine)上。

美国疾病防控中心(CDC)主持了此次研究,追踪了A(H1N1)流感病毒自4月15日以来的传播状况。

结果显示,感染者中60%是18岁及以下人群,只有5%超过了50岁。研究就此观察结果提出几种可能的原因——包括儿童和年轻人比老年人更易感;或向老年人的传播速度比较慢,因为老年人接触人较少。

研究报告称,感染者最常见症状是发烧和咳嗽,这与季节性流感症状很相似。在调查涉及的394名患者中,371名出现发烧;而在397名患者中,365名出现咳嗽。其它一些症状包括腹泻(323名患者中82名出现此症状)和呕吐(295名患者中74名出现此症状),而这两者并不是季节性流感的典型症状。

研究称,该病毒在人际间的传播模式仍然未知。虽然该病毒被怀疑通过人类打喷嚏传染,但因为许多患者出现腹泻,所以应该考虑和调查病毒通过粪便传播的可能性。报告说:“在获得进一步的数据之前,应该考虑所有可能的传播路径和病毒剥离源。”

英国国立医学研究所病毒学家John McCauley表示,关于年龄分布的数据是需要考虑的最重要因素之一。如果50岁以上的年龄段症状更加温和,这可能表明他们也许已经对1950年代以来流行的其它猪流感病毒株建立了一些抵抗力。不过他补充说:“可能有其它一些原因来解释这种奇特的年龄分布,比如老年人接触到的人可能较少。”

原始出处:

NEJM May 7, 2009 (10.1056/NEJMoa0903810)

Emergence of a Novel Swine-Origin Influenza A (H1N1) Virus in Humans

ABSTRACT

Background On April 15 and April 17, 2009, novel swine-origin influenza A (H1N1) virus (S-OIV) was identified in specimens obtained from two epidemiologically unlinked patients in the United States. The same strain of the virus was identified in Mexico, Canada, and elsewhere. We describe 642 confirmed cases of human S-OIV infection identified from the rapidly evolving U.S. outbreak.

Methods Enhanced surveillance was implemented in the United States for human infection with influenza A viruses that could not be subtyped. Specimens were sent to the Centers for Disease Control and Prevention for real-time reverse-transcriptase–polymerase-chain-reaction confirmatory testing for S-OIV.

Results From April 15 through May 5, a total of 642 confirmed cases of S-OIV infection were identified in 41 states. The ages of patients ranged from 3 months to 81 years; 60% of patients were 18 years of age or younger. Of patients with available data, 18% had recently traveled to Mexico, and 16% were identified from school outbreaks of S-OIV infection. The most common presenting symptoms were fever (94% of patients), cough (92%), and sore throat (66%); 25% of patients had diarrhea, and 25% had vomiting. Of the 399 patients for whom hospitalization status was known, 36 (9%) required hospitalization. Of 22 hospitalized patients with available data, 12 had characteristics that conferred an increased risk of severe seasonal influenza, 11 had pneumonia, 8 required admission to an intensive care unit, 4 had respiratory failure, and 2 died. The S-OIV was determined to have a unique genome composition that had not been identified previously.

Conclusions A novel swine-origin influenza A virus was identified as the cause of outbreaks of febrile respiratory infection ranging from self-limited to severe illness. It is likely that the number of confirmed cases underestimates the number of cases that have occurred.