禽类流行性感冒PPT幻灯片.ppt

禽 類 流 行 性 感 冒 Avian Influenza; Bird Flu ,1,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 years influenza vaccine. The flu shot does not protect against type C influenza.,2,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.,3,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.,4,5,6,7,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.,8,Morphology of Influenza A virions,Orthomyxoviridae spherical and 80-200nm in diameter 8 segments of （-）ssRNA “spikes“ of haemagglutinin (HA) and neuraminidase (NA),9,10,11,Influenza A polypeptides,12,13,The Life Cycle of Influenza Virus,14,Inactivation of Influenza A virus,Radiation pH9 or 5 Temp. above 50C (56C, 3h; 60C, 30m) Detergents and organic solvents Drying in 2448 h 在糞便中的病毒，0下可存活三十天，20下僅存活七天。,15,Characteristics of Influenza,mortality: 0.01% flu spread: droplet spread. flu season: from late December through March.,16,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. (-17 days to spread) Complications：Pneumonia, myositis, encephalopathy, transverse myelitis, Reye syndrome, myocarditis, and pericarditis.,17,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.,18,Hosts of Influenza A Virus,19,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.,20,Antigenic drift and shift,21,Avian Influenza (Bird Flu),Two surface antigens 1. HA: 15 subtype from H1H15. 2. NA: 9 subtype from N1N9. 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.,22,H5N1 Hong Kong Flu (1997),More than 1 million chickens, ducks, and geese were killed in Hong Kong , Dec. 1997.,23,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.,24,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.,25,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.,26,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.,27,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.,28,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.,29,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.,30,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.,31,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.,32,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.,33,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.,34,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。,35,36,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。,37,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.,38,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 pandem