新型A型流感

Novel Influenza A Virus Infections

新型A型流感（Novel Influenza A Virus Infections）係指除了每年週期性於人類間流行的A型季節性流感（H1N1及H3N2）以外，偶然感染人類的其他A型流感亞型。不同亞型流感對人類的感染力及所造成疾病嚴重度不盡相同，目前曾造成人類嚴重疾病的亞型包括於1997年首次出現的H5N1流感，以及2013年發現的H7N9流感等，其致死率較一般季節性流感高。重症病例的臨床表現多為早期出現發燒、咳嗽及呼吸短促等急性呼吸道感染症狀，而後快速進展為嚴重肺炎，可能併發急性呼吸窘迫症候群、敗血性休克及多重器官衰竭而死亡。亦有部分新型A型流感亞型感染人類後僅引發輕微症狀或無症狀，其臨床表現則包括結膜炎以及類流感症狀等。診斷方式以病毒核酸檢測為主，目前建議早期使用克流感或瑞樂沙等抗流感病毒藥劑加以治療。為避免疫情傳播，請臨床醫師診治類流感病患時應保持警覺，詢問其旅遊史、職業、接觸史以及有無群聚情形（TOCC）。如發現符合新型A型流感通報定義之疑似病例，立即採取適當防護措施並通報衛生單位。

Novel influenza A virus infections are human cases of infection with a novel influenza A virus that is different from the currently circulating seasonal human influenza H1N1 and H3N2 viruses. Different subtypes of novel influenza A viruses carry with them different degrees of pathogenicity which in turn cause different degrees of disease severity. The H5N1 influenza since 1997 and the H7N9 influenza since 2013 remain so far two of the most severe novel influenza A virus infections, causing more serious diseases and greater mortality than seasonal influenza. Novel influenza A virus infections in humans have been presented with fever, cough, and dyspnea initially, possibly followed by severe respiratory illness (e.g. pneumonia, acute respiratory distress syndrome), septic shock, multiorgan disease, and death. Some of them, however, have been found to result only in mild illness or conjunctivitis. Polymerase chain reaction assay for viral nucleic acids is the preferred diagnostic test for novel influenza A virus infections. We recommend that all confirmed or probable cases receive antiviral treatment with a neuraminidase inhibitor (oseltamivir or zanamivir) as early as possible. Healthcare workers should stay vigilant in assessing patients exhibiting influenza-like illness by carefully inquiring into travel, occupation, contact and cluster history (TOCC), immediately report to their local health department any suspect and probable cases, and execute necessary infection prevention and control measures.