新版H1N1流感指引力主儘快使用抗病毒藥劑
新版H1N1流感指引力主儘快使用抗病毒藥劑
作者：Robert Lowes
出處：WebMD醫學新聞
November 12, 2009 — 世界衛生組織(WHO)的新版H1N1流感治療指引，主張醫師們應儘快開立抗病毒藥物給流感症狀高風險族群、肺炎病患，以及那些無併發症的類流感患者，或過去72小時症狀無改善者。
根據週二改版的指引，立即使用抗病毒藥物治療的理由是，輕微的H1N1流感有可能會在24小時內變成致命的肺炎。
WHO全球流感計畫醫療官員Nikki Shindo醫師在記者會中表示，這個病毒可能會在一週內奪去性命。就疾病病程而言，一週的治療機會有限，須在病毒侵犯肺部之前就給予藥物。
根據Shindo醫師指出，應在出現流感症狀就立即使用抗病毒藥物的高風險病患，包括孕婦、2歲以下孩童、有呼吸道問題的慢性疾病患者。
Shindo醫師表示，之前的WHO指引聚焦在治療H1N1病毒造成的重症。她解釋，這次更新的指引可以說是為了預防重症，特別是使用抗病毒藥物。最初的抗病毒藥物指引比較保守，因為WHO對於它們的效果幾乎毫無經驗，而且供貨量有限。現在，WHO有較多有關這些藥物安全性和使用方面的資料，而供應上也比較充沛。
更新版的指引中，呼籲醫師們對於疑似H1N1流感患者，不要為了進行試驗確認診斷而延遲使用抗病毒藥物治療，此外，流感快篩檢測陰性也不應作為停止抗病毒藥物治療的依據，因為這些檢測漏失了許多大流行H1N1病毒的感染。
根據WHO指出，治療H1N1病毒的第一線抗病毒藥物為oseltamivir (Tamiflu)。如果無法取得oseltamivir、無法給予特定病患、或病毒對oseltamivir有抗藥性，該指引建議醫師使用吸入型的zanamivir(Relenza)。
Shindo醫師表示，為了確保輕症患者接受治療，公共衛生當局應提供抗病毒藥物給一般開業醫師，而不是只有給醫院，病患不一定非得到醫院才可以獲得抗病毒藥物處方，這麼做可以確保每個人迅速獲得所需的照護，也能讓醫院有餘力治療較嚴重的案例。
雖然Shindo醫師強調需儘快使用抗病毒藥物，但她表示，非屬高風險族群且只有輕微流感症狀者，不需要使用抗病毒藥物治療，健康成人也無需使用抗病毒藥物作為預防策略。
【WHO指引和CDC的指令沒有衝突】
更新版的WHO指引明定了無併發症的類流感患者、以及沒有足以造成風險之潛在醫療狀況者的72小時觀察期。病情惡化而需使用抗病毒藥物治療的指標包括：
* 呼吸短促、低血氧、兒童呼吸急促或無力，可能會造成氧氣不足或心肺損傷。
* 精神狀態改變、無意識、困倦、抽搐，可能有中樞神經系統併發症。
* 證明有持續的病毒複製或有侵犯性的次級細菌感染。
* 嚴重脫水、活動力下降、頭昏眼花、排尿減少、昏睡。
Shindo醫師表示，也建議必須進行病患教育，根據WHO指出，對於原本是無併發症的類流感患者，如果發生上述症狀或其他疾病惡化的症狀時、或沒有復原時，應在症狀發生的72小時內回診就醫。
疾病控制預防中心(CDC)的國家流感與呼吸道疾病中心流行病學家Anthony Fiore醫師表示，CDC並未對流感病患的追蹤照護提出類似的72小時規定，但是當局認為那些在幾天內沒有改善的病患，可能有二度感染的併發症。
Fiore醫師向Medscape Infectious Diseases表示，我不認為WHO的建議和CDC的指定有所衝突。CDC平均每4到6週就更新抗病毒藥物的給藥建議，我們會看看WHO的指引，並根據證據基礎來發展我們的指引。
可以在WHO網站獲得這個更新版的治療指引。
【CDC的更新資料】
今天，CDC國家流感與呼吸道疾病中心主任Anne Schuchat醫師在記者會中，提供了使用CDC新興感染計畫資料推估之估計H1N1案例數的更新資料。
CDC估計，在大流行的最初6個月(2009年4月到10月17日)，美國共有2,200萬人(範圍從1400-3400萬)人感染H1N1流感，其中，98,000人(範圍從63,000-153,000) 住院；3900人(範圍從2500 – 6100) 死亡。
根據年齡層區分該資料，64歲以下者的案例數、住院數與死亡率，比65歲以上者高很多。
她表示，這些數據每3到4週更新。
Schuchat醫師也討論了H1N1流感對於糖尿病患的影響，約佔H1N1住院成人的19%。根據Schuchat醫師，糖尿病患應接種疫苗(使用注射型疫苗而非鼻噴型疫苗)以預防H1N1。有糖尿病且有呼吸道疾病者應使用抗病毒藥物治療，且應在檢驗結果出來前就開始治療。糖尿病患者也必須要接種肺炎疫苗。
迄今，已經有4,160萬劑H1N1疫苗，Schuchat醫師表示，這遠超過我們過去所有的量，但是還未達我們目前所希望的量，目前，已經提供了9,400萬劑季節性流感疫苗，年底前預計總共有11,400萬劑。
Emma Hitt博士撰寫此報告。
New Guidelines on H1N1 Influenza Urge Quicker Use of Antivirals
By Robert Lowes
Medscape Medical News
November 12, 2009 — Updated treatment guidelines for H1N1 influenza from the World Health Organization (WHO) urge clinicians to administer antiviral medications as soon as possible to patients in at-risk groups with flu symptoms, patients with pneumonia, and those with uncomplicated influenza-like illness that worsens or fails to improve within 72 hours.
The reason for immediate antiviral therapy is that a mild case of H1N1 influenza can morph into a deadly disease such as pneumonia within 24 hours, according to the revised guidelines released Tuesday.
"The virus can take a life within a week," Nikki Shindo, MD, a medical officer in WHO's Global Influenza Programme, said during a press conference today. "The week of opportunity is very narrow in regard to the progression of the disease. The medicine needs to be administered before the virus destroys the lungs."
Patients in at-risk groups who should receive antivirals once they experience flu symptoms include pregnant women, children younger than 2 years, and individuals with chronic illnesses such as respiratory problems, according to Dr. Shindo.
Dr. Shindo said that earlier WHO guidelines focused on treating severe disease stemming from the H1N1 virus. The updated guidelines, she explained, have more to say about preventing severe disease, especially with the use of antiviral medications. Initial guidance about antivirals had been more conservative because WHO "had almost no experience" in regard to their effectiveness and because supplies were limited, said Dr. Shindo. Now, WHO has more data about the safety and usefulness of the medicine, and supplies are more ample.
The updated guidelines state that clinicians should not delay antiviral treatment for patients with suspected H1N1 influenza for the sake of conducting tests to confirm the diagnosis. In addition, a negative result from some rapid influenza diagnostic tests should not justify withholding antiviral therapy because these tests "miss many infections with pandemic H1N1 virus."
The first-line antiviral for treating the H1N1 virus is oseltamivir (Tamiflu), according to WHO. If oseltamivir is not available, it is not possible to administer it to a particular patient, or if the virus is resistant to oseltamivir, the guidelines recommend that clinicians use zanamivir (Relenza), which is inhaled.
To ensure easier access to treatment, public health authorities should distribute antivirals through general practitioners and not primarily through hospitals, said Dr. Shindo. "Patients should not have to visit the hospital to get antivirals prescribed," she said. "This should help ensure that individuals get the care they need faster. This will leave hospitals freer to treat the more severe cases."
Although Dr. Shindo emphasized the need for the earlier use of antivirals, she said that people not in the at-risk groups who are experiencing only mild flu symptoms do not need to take antiviral therapy. Nor should healthy individuals take it as a preventive measure.
WHO Guidelines Do Not Conflict With CDC Directives
The updated WHO guidelines specify watchful waiting for 72 hours for patients who have uncomplicated influenza-like illness and who do not have an underlying medical condition that puts them at risk. Hallmarks of progressive illness that warrant antiviral therapy include:
Shortness of breath, hypoxia, and fast or labored breathing in children, which would suggest oxygen impairment or cardiopulmonary insufficiency.
Altered mental status, unconsciousness, drowsiness, and seizures, which suggest central nervous system complications.
Evidence of sustained virus replication or invasive secondary bacterial infection.
Severe dehydration, expressed as decreased activity, dizziness, decreased urine output, and lethargy.
By necessity, this recommendation for follow-up requires patient education, Dr. Shindo said. Clinicians should instruct patients who initially present with uncomplicated influenza-like illness to return for another visit if they develop these or other symptoms of progressive illness — or do not get better — within 72 hours from the onset of symptoms, according to WHO.
The Centers for Disease Control and Prevention (CDC) have not issued any guidance on follow-up care for influenza patients that stipulates a 72-hour time frame, but the agency does advise patients who do not improve within a few days that they might have a complication like a secondary infection, said Anthony Fiore, MD, a medical epidemiologist with the CDC's National Center for Immunization and Respiratory Diseases.
"I do not see the WHO recommendations as being in conflict [with the CDC directives]," Dr. Fiore told Medscape Infectious Diseases. CDC recommendations on administering antiviral medications are revised on average every 4 to 6 weeks, said Dr. Fiore. "We will look at the WHO guidance and the evidence base used to develop the guidance as part of [our] revision."
The updated treatment guidelines are available on the WHO Web site.
CDC Update
At a CDC press briefing today, Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, provided an updated estimate of H1N1 cases using data extrapolated from the CDC’s Emerging Infections Program .
The CDC estimates that during the first 6 months of the pandemic (April through October 17, 2009), a total of 22 million people (range, 14 – 34 million) in the United States became infected with H1N1 influenza. Of these, 98,000 people (range, 63,000 to 153,000) were hospitalized; and 3900 (range, 2500 – 6100) died.
The data are also broken down by age group and highlight that fact that numbers of cases, hospitalizations, and deaths are disproportionately higher in people aged 64 years and younger than in older individuals.
These numbers will be updated every 3 to 4 weeks, she said.
Dr. Schuchat also discussed the effect of H1N1 influenza in patients with diabetes, which afflicts about 19% of adults hospitalized for H1N1. According to Dr. Schuchat, people with diabetes should be vaccinated (with the injectable vaccine not the nasal spray) against H1N1. People with diabetes who also have respiratory illness should receive antiviral therapy, which should be initiated prior to availability of test results. Patients with diabetes should also ensure that they have been vaccinated against pneumococcal infections.
To date, 41.6 million doses of H1N1 vaccine have become available. “This is more than we had before but not as much as we had hoped to have by today,” Dr. Schuchat said. Currently, 94 million doses of seasonal influenza vaccine have been distributed, with 114 million doses total expected by the end of the year.
Emma Hitt, PhD, contributed to this report.
