自 2003 年以来,高致病性禽流感(Highly Pathogenic Avian Influenza, HPAI)H5N1 病毒株已感染超过 50 个国家的家禽或野生鸟类。自 2003 年以来,有 16 个国家报道发现人类 HPAI H5N1 病毒感染病例。2003-2018 年期间,共报道 860 例,死亡 454 例(病死率为 53%)。[26]World Health Organization. Cumulative number of confirmed human cases of avian influenza A(H5N1) reported to WHO. 2018 [internet publication].
http://www.who.int/influenza/human_animal_interface/H5N1_cumulative_table_archives/en/
WHO: cumulative number of confirmed human cases of avian influenza A(H5N1) reported to WHO
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大多数人类 HPAI H5N1 病例为既往体健的儿童和年轻人。患者平均年龄大约为 20 岁,年龄范围则从 1 岁至 81 岁。[27]World Health Organization. Update: WHO-confirmed human cases of avian influenza A (H5N1) infection, November 2003-May 2008. Wkly Epidemiol Rec. 2008;83:415-420.
http://www.who.int/wer/2008/wer8346.pdf
http://www.ncbi.nlm.nih.gov/pubmed/19009716?tool=bestpractice.com
男女患病比例基本相当;但是女性患者的病死率较高,这可能与许多不同的流行病学因素相关,例如未及时就诊、患者年龄以及医师的检查方式。[18]World Health Organization. Update on human cases of highly pathogenic avian influenza A(H5N1) virus infection, 2010. Wkly Epidemiol Rec. 2011;86:161-166.
http://www.who.int/wer/2011/wer8617.pdf
http://www.ncbi.nlm.nih.gov/pubmed/21516633?tool=bestpractice.com
从 2003 年到 2010 年,20 岁以下患者的死亡风险显著低于年龄超过 20 岁的患者(病死率:52% vs 66%)。[18]World Health Organization. Update on human cases of highly pathogenic avian influenza A(H5N1) virus infection, 2010. Wkly Epidemiol Rec. 2011;86:161-166.
http://www.who.int/wer/2011/wer8617.pdf
http://www.ncbi.nlm.nih.gov/pubmed/21516633?tool=bestpractice.com
死亡率与诊断和住院治疗的延迟相关。[18]World Health Organization. Update on human cases of highly pathogenic avian influenza A(H5N1) virus infection, 2010. Wkly Epidemiol Rec. 2011;86:161-166.
http://www.who.int/wer/2011/wer8617.pdf
http://www.ncbi.nlm.nih.gov/pubmed/21516633?tool=bestpractice.com
一项研究称,HPAI H5N1 儿童患者出现流涕,似乎提示更好的预后。[24]Oner AF, Dogan N, Gasimov V, et al. H5N1 avian influenza in children. Clin Infect Dis. 2012;55:26-32.
https://academic.oup.com/cid/article/55/1/26/317646/H5N1-Avian-Influenza-in-Children
http://www.ncbi.nlm.nih.gov/pubmed/22423125?tool=bestpractice.com
2014 年 1 月,加拿大报道了一例人类感染 HPAI H5N1 确诊病例。患者从中国至加拿大旅游,在加拿大住院治疗,遭遇死亡。[28]Centers for Disease Control and Prevention. Highly pathogenic Asian avian influenza A (H5N1) virus. May 2018 [internet publication].
https://www.cdc.gov/flu/avianflu/h5n1-virus.htm
虽然没有迹象显示该感染发生在北美地区,但该病例突出显示,对于重症患者,临床医生应当提高警惕,考虑是否存在流感病毒感染可能,包括 HPAI H5N1 和其他新型甲型流感病毒。同样在 2014 年,联合国粮农组织(Food and Agriculture Organization, FAO)报道称,至少 6 个国家存在家禽 HPAI H5N1 病毒流行,包括孟加拉国、中国、埃及、印度、印度尼西亚和越南,其他国家则有散在家禽疫情暴发。[29]Food and Agriculture Organization of the United Nations. Update on the continuous spread and expansion of H5N1 highly pathogenic avian influenza: clade 2.3.2.1 in Asia (2010-2012). January 2014 [internet publication].
http://www.fao.org/3/a-i3610e.pdf
到目前为止,无论北美还是南美地区的家禽都没有被检测到亚洲谱系 HPAI H5N1 病毒株,但是在美国鸟类中发现了与人类感染不相关的、抗原性不同的 HPAI H5N1 病毒。[30]Centers for Disease Control and Prevention. Highly pathogenic avian influenza A (H5N1) in birds and other animals. April 2017 [internet publication].
http://www.cdc.gov/flu/avianflu/h5n1-animals.htm