Malaria
什么是Malaria？
Malaria is a complex tropical disease caused by infection with one of several types of malaria parasites, known as Plasmodia. Some of the types cause more serious illness than others. Although these parasites can be found in many different animals, four types infect humans causing mild to severe illness. They are called falciparum, vivax, ovale and malariae. A fifth type called knowlesi that is known to infect monkeys and was previously confused with the malariae type is now recognized as a serious infection in humans. The most dangerous of the strains is falciparum.
The incubation period depends on the type of parasite. For the falciparum strain, the incubation period is generally 7-14 days; for the vivax and ovale strains, 8-14 days; for the malariae strain, 7-30 days; for the knowlesi strain, 10-12 days. Because of the somewhat lengthy incubation period for all strains, many travellers do not develop clinical illness until they return to their home country. Because the early manifestation of the infection is marked by spiking fevers, it is often difficult to distinguish malaria from other infectious diseases. Where malaria is not commonly seen, physicians are not well versed in the diagnosis and treatment of this illness.
Malaria parasites are found in many tropical and subtropical areas. Malaria is no longer a problem in countries with temperate climates.
Many of the parasites have developed resistance to commonly used anti-malaria medications, especially in Southeast Asia and sub-Saharan Africa. Recently, high levels of resistance to the most effective drug combination (artemisinin-mefloquine) for treating malaria has been found along the Thai-Myanmar border.
如何获得Malaria？
Malaria is transmitted by the bite of an infected female mosquito. Transmission occasionally occurs through blood transfusions, organ transplants, needle sharing and from mother to the unborn child.
易感性和抗性
Humans are universally susceptible to malaria infection. Persons who live in malarious regions and who are infected repeatedly, develop some degree of immunity and tolerance to the clinical effects of the disease.
症状是什么？
It is often difficult to distinguish the initial symptoms of malaria from any other infectious disease that begins with fever. Laboratory tests are essential to identify the presence of the parasites in the blood.
Falciparum malaria can cause a varied clinical picture, but in general, the patient develops sudden onset of fever, chills, sweats, cough, diarrhoea, difficulty breathing and headaches. The severe form of the illness may include jaundice, shock, liver and kidney failure, acute inflammation of the brain, swelling of the brain, coma and death. Prompt treatment is essential, even for mild cases, since the disease may progress suddenly and rapidly to severe consequences and death.
The vivax and ovale strains usually do not cause life threatening illness. The illness is characterized by fatigue and a rising fever, followed by shaking chills, headache and nausea. The fever ends with severe sweating. After an interval of 1, 2 or 3 days, the fever cycle is repeated for a week or a month or longer. Relapses occur over a period as long as 5 years. Gradual development of immunity reduces the frequency of attacks. and a low grade life-long infection may occur without symptoms.
The knowlesi strain causes peak fevers every 24 hours. Although infection with this strain can be fatal, the outcome may also be quite variable, including self-cure or chronic illness.
预防措施
预防疟疾在很大程度上取决于一年中的季节，旅行者的目的地国家，该国计划的活动以及住宿的类型。主要的预防措施有两个：（1）避免蚊子接触；（2）服用药物预防感染。由于药物可能有副作用，因此重要的是平衡药物治疗和防蚊措施。在某些情况下，仅避免蚊子就足够了。在其他情况下，将需要避免蚊子和抗疟疾药物。由于传播疟疾的蚊子通常在黄昏和黎明之间咬人，因此在这段时间内留在经过良好检查的区域，使用驱虫剂并穿防护服很重要。如果在未经遮挡的住所中睡觉，请使用氯菊酯浸渍的蚊帐来驱除蚊子。前往疟疾地区旅行之前，期间和之后必须服用抗疟疾药物。药物的选择取决于疟疾的类型和目的地国家的耐药性。常用的抗疟疾药物包括Atovaquone-Proguanil，氯喹和羟氯喹，强力霉素，甲氟喹，Primaquine等。该选择应咨询有关疟疾预防知识的医生。
处理
Treatment depends on the type of malaria parasite. Prompt treatment with appropriate anti-malarial medication is essential since delays in diagnosis and treatment are associated with increased mortality, especially for the falciparum strain. Treatment has become more complicated for this strain due to the development of serious drug resistance. There are, however, effective anti-malarial medications that should be taken under the care of a physician who is knowledgeable about malaria therapy.
药物
它常见于哪里？
疟疾在世界热带地区最为普遍，常年传播。在其他地区，如亚热带和温带地区，传播可能只发生在提供最佳气候以支持蚊子生长发育的季节。疟疾在撒哈拉以南非洲和新几内亚大部分地区流行（即不断发生）;南亚、东南亚、大洋洲、海地、中南美洲的广大地区;以及墨西哥、多米尼加共和国、北非和中东的部分地区。
在东南亚许多国家的森林地区，特别是在农民、猎人和伐木者之间，或人类、蚊子和猴子交往的地方，都发现了这种病菌菌株。
局部传播可能因降雨量、温度和海拔等影响当地蚊子数量的因素而异。
