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禽類流行性感冒 ﹙ Avian Influenza; Bird Flu ﹚ 中國醫藥大學附設醫院 實習醫生︰高 敏 欽 March 2, 2k4 於台中市立大業國中 Three Types of Influenza Viruses Influenza A, B, and C. Each year about 20,000 Americans die because of influenza or influenza related pneumonia. Over 90% of the deaths occur in persons aged 65 years and older. The current subtypes of influenza A viruses found in people are A(H1N1) and A(H3N2). Influenza A(H1N1), A(H3N2), and influenza B strains are included in each year's influenza vaccine. The flu shot does not protect against type C influenza. Introduction Influenza A virus Infect various animal hosts (avian, mammalian). Serologic and genetic analysis: 15 hemagglutinin (HA) 9 neuraminidase (NA) Only 3 of the 15 HA subtype have caused pandemics in human H1N1 in 1918 (Spanish, swine), 20 million deaths, Avian ancestor. H2N2 in 1957 (Asian), 86,000 deaths (U.S.), avian reassortment. H3N2 in 1968 (HK), 34,000 deaths (U.S.), avian reassortment. H1N1 reemerge in 1977 (Russian), negligible. Background on Pandemics 1918-19, "Spanish flu," [A (H1N1)], caused the highest number of known flu deaths: more than 500,000 people died in the United States, and 20 million to 50 million people may have died worldwide. Many people died within the first few days after infection and others died of complications soon after. Nearly half of those who died were young, healthy adults. Background on Pandemics (cont.) 1957-58, "Asian flu," [A (H2N2)], caused about 70,000 deaths in the United States. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957. 1968-69, "Hong Kong flu," [A (H3N2)], caused approximately 34,000 deaths in the United States. This virus was first detected in Hong Kong in early 1968 and spread to the United States later that year. Type A (H3N2) viruses still circulate today. Morphology of Influenza A virions Orthomyxoviridae spherical and 80- 200nm in diameter 8 segments of (-) ssRNA "spikes" of haemagglutinin (HA) and neuraminidase (NA) Influenza A polypeptides Segment Size (nt) Polypeptide Function 1 2341 PB2 2 2341 PB1 3 2233 PA 4 1778 HA Subunit of polymerase, active synthesis Haemagglutinin 5 1565 NP Nucleoprotein: Part of transcriptase complex 6 1413 NA Neuraminidase: release of virus 7 1027 M1 Matrix protein: Major component of virion M2 Integral membrane protein: Ion channel NS1 Anti-interferon protein. Effects on cellular RNA transport RNP nuclear export 8 890 NS2 Subunit of polymerase: Host cap binding and endonuclease Catalytic subunit of polymerase in vRNA The Life Cycle of Influenza Virus Inactivation of Influenza A virus Radiation pH>9 or <5 Temp. above 50°C (56°C, 3h; 60°C, 30m) Detergents and organic solvents Drying in 24~48 h 在糞便中的病毒,0℃下可存活三十天, 20℃下僅存活七天。 Characteristics of Influenza mortality: 0.01% flu spread: droplet spread. flu season: from late December through March. Clinical Signs and Symptoms of Influenza Fever, nonproductive cough, myalgia, headache, severe malaise, pharyngitis, sore throat, and rhinitis. (Otitis media, nausea, seizures, diarrhea, and vomiting among children. ) not coryza (runny nose). Spread: via aerial droplets and fomites. Incubation:1-4 days. Onset : 5 days. (-1~7 days to spread) Complications:Pneumonia, myositis, encephalopathy, transverse myelitis, Reye syndrome, myocarditis, and pericarditis. Transmission of Influenza A Viruses from Animals to People Influenza A viruses are found in many different animals, including ducks, chickens, pigs, whales, horses, and seals. Wild birds are the primary natural reservoir for all subtypes of influenza A viruses. Pigs can be infected with both human and avian influenza viruses in addition to swine influenza viruses. Hosts of Influenza A Virus How the Flu Virus Can Change "Drift" and "Shift" antigenic drift: small changes in the virus that happen continually over time. Every 2 – 3 years. antigenic shift: an abrupt, major change in the influenza A viruses, resulting in new HA and/or new HA and NA proteins in influenza viruses that infect humans. Every 10 - 15 years. Antigenic drift and shift Avian Influenza (Bird Flu) Two surface antigens 1. HA: 15 subtype from H1~H15. 2. NA: 9 subtype from N1~N9. All subtypes can be found in wild birds. Only 3 subtypes of HA (H1, H2 and H3) and two subtypes of NA (N1 and N2) are circulating widely in humans. Avian influenza viruses do not usually directly infect humans or circulate among humans. Southern China is a hypothetical influenza epicenter. H5N1 Hong Kong Flu (1997) More than 1 million chickens, ducks, and geese were killed in Hong Kong , Dec. 1997. Avian Influenza Infections in Humans 1997: H5N1 infected both chickens and humans in Hong Kong. 18 people were hospitalized and 6 of them died. About 1.5 million chickens was killed. 1999: H9N2 were confirmed in 2 children. Several additional human H9N2 infections were reported from mainland China in 1998-99. 2003: More than 80 cases of H7N7 illness were reported, and 1 patient died in the Netherlands. H9N2 infection was confirmed in a child in Hong Kong. Avian Influenza Infections in Humans 2003-04 Avian Influenza Outbreak In birds: outbreak of H5N1 infection in Cambodia, China, Hong Kong, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam. In people: 33 cases of H5N1 infection in Vietnam (23) and Thailand (10), 22 (15+7) deaths have been reported. Characteristics of Avian Influenza in Birds Water birds act as hosts of influenza viruses by carrying the virus in their intestines and shedding it. Viruses in saliva, nasal secretions and feces. Fecal-to-oral transmission is the most common mode of spread. Characteristics of Avian Influenza in Birds (cont.) Most influenza viruses cause no symptoms, or only mild ones in wild birds; however, the range of symptoms in birds varies greatly depending on the strain of virus and the type of bird. Infection with certain avian influenza A viruses (e.g. some H5 and H7 strains) can cause widespread disease and death among some species of wild birds and especially domesticated birds such as chickens and turkeys. Information on Influenza A (H5N1) Background: 1. H5N1 is a subtype of Type A influenza virus. 2. Wild birds are the natural hosts of virus. 3. 1st identified in Italy > 100 ys ago isolated from birds (terns) in South Africa in 1961. Information on Influenza A (H5N1) (cont.) Infection: 1. In 1997, 1st direct bird-to-human transmission of H5N1 in Hong Kong; caused illness in 18 people, of who 6 died. (Mortality is 30%). The outbreak was halted in Hong Kong by slaughter of the chickens. 2. But so far, H5N1 viruses have not been capable of efficient human-to-human transmission. Information on Influenza A (H5N1) (cont.) Spread: 1. Infected birds shed virus in saliva, nasal secretions and feces. 2. Avian influenza viruses spread among susceptible birds when they have contact with contaminated excretions. 3. Most cases of H5N1 infection in humans have resulted from contact with infected poultry or contaminated surfaces. Current H5N1 Strain All genes are of bird origin. Different variations of H5N1 virus are circulating at this time. H5N1 show antiviral resistance to amantadine and rimantadine, but oseltamavir and zanamavir should still be effective. Symptoms of Avian Influenza in Humans Typical influenza-like symptoms (e.g., fever, cough, sore throat and muscle aches). Eye infections, pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications. Prevention of Avian Influenza Prescription medications approved for human influenza strains would be effective in preventing avian influenza infection in humans. Vaccination: The single best way to prevent the flu is to get vaccinated each fall. In the absence of vaccine, however, there are other ways to protect against flu. Other Habits for Good Health Avoid close contact. Stay home when you are sick. Cover your mouth and nose. Clean your hands. Avoid touching your eyes, nose or mouth. 預防禽流感~ 衛生署 染病的活鳥和家禽的糞便中可能會帶有病毒, 故應盡量避免接觸活鳥和家禽及其糞便。如 曾接觸活鳥或家禽,要立刻用肥皂和清水洗 手。如家中飼養雀鳥,應避免和牠有親密接 觸,並每次在接觸牠或替牠處理糞便後用肥 皂和清水洗手。學校及幼兒院舍亦應採取措 施防止兒童接觸活鳥及家禽。出外旅遊時應 避免接觸活鳥及 家禽。進食家禽肉類和 蛋時應徹底煮熟。 如有流感徵狀便要看醫生 ,並要戴上口罩,以防傳 染他人。 工作人員如何避免受到感染? 接種流感疫苗。 若出現發燒、喉嚨痛、咳嗽等類流感症狀或眼睛發炎 的現象,禁止接觸禽畜。 與禽畜接觸時需穿著長袖、不透水的工作服並需戴厚 橡膠手套。 配戴平面口罩,避免留在空氣不流通的工作場所。 建議使用護目鏡。 穿不透水(如:橡膠、聚氨酯材質)之工作鞋。 時常以肥皂清潔雙手,工作結束時雙手需消毒。 Treating the Avian Influenza Rest, drink plenty of liquids, avoid using alcohol and tobacco, and take medication to relieve the symptoms of flu. Antiviral Medications: 1. M2 inhibitors (amantadine and rimantadine) 2. neuraminidase inhibitors (oseltamivir and zanimivir). All of these must be prescribed by a doctor. Antiviral treatment lasts for 5 days and must be started within the first 2 days of illness. Potential for an Influenza Pandemic All influenza viruses can change. There is little or no immune protection against them in the human population. It is possible that an avian influenza virus could infect humans and spread easily from person to person, an “influenza pandemic” could begin!!! established in 1952 Surveillance in the United States Three surveillance systems, coordinated and maintained by CDC: 1. Weekly Pneumonia and Influenza Mortality Chart (in 122 cities ) 2. Epidemiologists' Reports of Influenza Activity (state health departments) 3. Physicians' Reports of Influenza-like Illness (about 260 physicians ) The information from these surveillance systems is published periodically by the CDC, and is available on the Internet. Percent of Respiratory Specimens Testing Positive for Influenza, NYS WHO and NREVSS Collaborating Laboratories 流感及禽流感之因應措施--衛生署疾病管制局 1.遵循「流感期SARS防治作戰動員計畫」。 2.建立流感大流行防治作戰動員計畫(Pandemic Flu Preparedness)。 3.針對雞、鴨、豬農施打流感疫苗。 4.加強各縣市養殖戶衛教及自主健康管理。 5.發燒病人進行禽畜接觸史之詢問調查,一旦疑似流感, 立即給予克流感。 6.2004年10月1日起,二歲以下兒童列入流感疫苗施打對象。 7.加強國際間農業與醫療部門之合作及聯繫。 8.加強機場海關入境者之體溫監控。 9.呼籲民眾減少不必要之東南亞旅遊,並避免接觸禽畜。 10.民眾若出現發燒咳嗽請戴上口罩並避免出入公共場所。 病毒即時檢測系統 呼吸道病毒檢體檢驗流程 禽流感、流感與SARS 臨床症狀區別 Thanks for your attention !