- DavidLv 72 0 年前最佳解答
什麼是拉薩熱 (Lassa Fever) ﹖答：拉薩熱是一種生病期間一至四週的急性病毒性疾病，它的臨床特徵為漸進性發病且有身體不適、發燒、頭痛、喉嚨痛、咳漱、噁心、嘔吐、腹瀉、肌肉疼痛、胸痛及腹痛等症狀，也常有咽炎及結膜炎，嚴重者會有低血壓或休克、肋膜積水、出血、癲癇、腦病變、臉部及頸部水腫，也會出現蛋白尿及血液濃縮現象。拉薩熱的感染病原是什麼﹖答：由沙病毒科 (Arenaviridae) 的拉薩病毒 (Lassa virus) 所引起。拉薩熱的發生情形如何﹖答：拉薩熱的主要發生國家（地區）為非洲西部，自奈及利亞到獅子山一帶的地方性傳染病，截至1975年，共發現118名病例，其中48人死亡，致死率約40會%。拉薩熱的傳染途徑如何﹖答：拉薩熱主要是經由接觸感染老鼠附著在物體表面（如地板、床、食物等）的排泄物而得病，也會經由直接接觸病患，或經血液、體液的污染而發生人與人之間的傳染。拉薩熱的潛伏期多久﹖答：約六日至二十一日。民眾出國旅遊期間，如何預防感染拉薩熱﹖答：（１）儘量不到流行地區旅遊；如果在流行地區旅遊活動時，避免接觸老鼠，或其排泄物，也不要接觸病患，或其血液、體液，並注意環境衛生。 （２）旅遊活動的環境被污染時，可以使用0.5%次氯酸鈉（漂白水）來消毒，並注意個人的防護措施，如接觸污染物前後應洗手，接觸污染物時應穿戴手套及防護衣物，污染廢棄物應適當地處理等。Lassa Fever - Fact Sheet for Health Professionals Topics A-Z | Viral Haemorrhagic FeversReviewed on 29 September 2004
(Images from CDC, NCID, Special Pathogens Branch)Lassa FeverLassa fever is an acute viral haemorrhagic fever (VHF) caused by Lassa virus, a member of the arenavirus family. The disease was first described in the 1950s, and the virus was identified in 1969, when two missionary nurses died from it in the town of Lassa in Nigeria. It is known to be endemic in Guinea, Liberia, Sierra Leone, and parts of Nigeria, and evidence of human infection has been found in the Central African Republic, the Congo, Mali and Senegal. Clinical symptomsInfection is mild or asymptomatic in 80% of cases, but can cause severe illness and is fatal in approximately 1-3% of patients. The incubation period for disease is usually between 7 and 10 days, although a range of 3-21 days has been reported in some cases.Early diseaseThe onset of illness is insidious, with fever and shivering accompanied by malaise, headache, generalised aching and a sore throat. This may be accompanied by nausea, vomiting, diarrhoea or cough. There may be patches of white or yellowish exudate and occasionally small vesicles or shallow ulcers on the tonsils and pharynx and this is an important diagnostic feature. As the illness progresses the body temperature may rise to 41ºC with daily fluctuations of 2-3ºC. Fever is very variable, occurring constantly or in peaks, and lasting on average for 16 days; extremes of 6-30 days have been reported. Late/severe diseaseSevere attacks are characterised by extreme lethargy and exhaustion, disproportionate to the level of fever. During the second week of illness there may be oedema of the head and neck, encephalopathy, pleural effusion, and ascites. Renal and circulatory failure may occur, aggravated by vomiting and diarrhoea. In the severest cases bleeding into the skin, mucosae and deeper tissues occurs, usually leading to death. In non-fatal cases the fever subsides and the patient’s condition improves rapidly although tiredness may persist for several weeks. There is usually a leucopaenia although a high polymorphonuclear leucocytosis is encountered occasionally. Late complications include sensorineural deafness in around 25% of patients, persisting for life in around a third of those affected. Infection is fatal in around 15% of hospitalised patients. Lassa fever is particularly severe in pregnant women in the third trimester; the foetus dies in about 95% of cases. Symptoms in children are similar to those in adults, but infant infection can result in “swollen baby syndrome” with oedema, abdominal distension, bleeding and often death.DiagnosisClinical diagnosis of Lassa fever is difficult, and it can be confused with other infections such as severe malaria, typhoid fever and other viral haemorrhagic fevers.Highly specialised laboratory facilities are required for a definitive diagnosis, and samples must be handled with extreme care to prevent transmission. Lassa fever can be diagnosed using RT-PCR for nucleic acid detection, virus isolation or antibody detection methods. TransmissionLassa virus is present in wild multimammate rats (Mastomys species), which shed the virus in their urine and droppings. These are common in rural areas of tropical Africa, and often live in or around homes. Mastomys breed very frequently and produce large numbers of offspring. Once infected, rodents continue to shed virus throughout their life. Transmission of Lassa virus to humans normally occurs through contamination of broken skin or mucous membranes via direct or indirect contact with infected rodent excreta, on floors, home surfaces, in food or water. Transmission is also possible where rodents are caught and consumed as food. Person to person transmission occurs through exchange of infected bodily fluids, such as blood, saliva, urine or semen. This can happen either in the laboratory, in a healthcare setting or via sexual or other close contact. Transmission to close contacts usually only occurs while the patient has symptoms, and the virus is present in the throat. However, virus can be excreted in the patient’s urine for between 3 and 9 weeks after the onset of illness, and may be transmitted via semen for up to three months. Risk groupsPeople living in endemic areas of West Africa with high populations of rodents are most at risk of Lassa fever. Travellers to these regions are also at risk of infection, and the relatively long incubation period means that travellers returning from endemic areas could be incubating disease. This is rare in the UK, only 6 confirmed cases of Lassa fever have been imported since 1976, and there has been no evidence of onward transmission from any of these cases.People in close contact with the bodily fluids of infected patients are at risk of transmission, however this is rare and medical staff are at low risk if adequate protective measures are taken.Treatment Treatment with the antiviral drug ribavirin is most effective when started within the first 6 days of illness, and should be given intravenously for 6 days. However this drug does not prevent deafness associated with Lassa fever. Supportive care such as fluid replacement, blood transfusion or other appropriate measures is also essential.Prevention and ControlThere is no vaccine, although research is underway to produce one. In endemic areas infection can be prevented by rodent control, and avoiding contact with rodents or their excreta including storage of food in rat proof containers etc. Person to person spread is prevented by taking appropriate measures to avoid contact with bodily fluids of an infected patient. In healthcare settings this requires the use of special barrier nursing procedures or VHF isolation precautions, which involve isolating infected patients, and staff wearing protective clothing for contact with the patient. In Britain, patients with Lassa fever are cared for in a high security infectious disease unit.All objects with which the patient has had contact should be disinfected with sodium hypochlorite solution containing 1000ppm available chlorine, or 0.5% phenol with detergent, and if possible by autoclaving, incineration or boiling. Overt contamination with blood or body fluids should be treated with freshly prepared sodium hypochlorite solution containing 10,000ppm available chlorine.Once the patient has recovered from disease they are only infectious via semen and urine. Sexual intercourse must be avoided for 3 months.Contact surveillanceThose persons who have been in close contact with an infectious patient must be identified within three weeks of the onset of illness. As a precaution, contacts should be monitored by taking their temperature twice daily for 21 days after their last exposure to the patient. If a high temperature (above 38.3ºC/101ºF) develops the contact should stay at home and inform the person in charge of their monitoring immediately.
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