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黄热病
黄热病是一种由黄热病毒（YFV）引起的病毒性出血性疾病，该病毒属于黄病毒科（Flaviviridae）。该病主要通过非洲和南美洲热带及亚热带地区的伊蚊（Aedes）和煞蚊（Haemagogus）传播。病毒经蚊虫叮咬进入人体后，首先在皮肤中的免疫细胞（如树突状细胞和巨噬细胞）内复制。这些细胞随后迁移至…
黄热病是一种由黄病毒引起的病毒性出血热疾病，通过受感染的伊蚊（Aedes）或煞蚊（Haemagogus）传播。
蚊虫叮咬后，病毒进入皮肤并感染局部免疫细胞。这些细胞将病毒携带至附近的淋巴结，在淋巴结中病毒进行复制并出芽释放。
病毒颗粒随后进入血液——这一过程称为病毒血症——并扩散至肝脏等各个器官。
在肝脏中，该病毒会感染肝细胞，导致细胞凋亡。
库普弗细胞是肝脏的巨噬细胞，可释放细胞因子，加剧炎症和组织损伤。
这种损伤会破坏胆红素代谢，导致胆红素在肝脏中积聚，进而进入血液。
过量的胆红素会导致黄疸——即皮肤和眼睛发黄，该病因此得名。
黄热病的发展分为三个阶段：发热期伴有发热和疼痛，短暂的缓解期，以及出现出血、黄疸和器官衰竭的中毒期。
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Q1: How does the yellow fever virus spread from mosquitoes to humans?
Yellow fever is transmitted through infected Aedes or Haemagogus mosquitoes. When a mosquito bites, the virus enters the skin and infects local immune cells such as dendritic cells and macrophages. These infected cells then migrate to nearby lymph nodes, where viral replication increases before the virus enters the bloodstream in a process called viremia.
Q2: What happens to the liver during yellow fever infection?
The virus infects hepatocytes, causing both apoptosis and necrosis. Kupffer cells, the liver's specialized macrophages, release proinflammatory cytokines that intensify hepatocellular damage. This destruction disrupts bilirubin metabolism, causing hyperbilirubinemia and leading to jaundice, the characteristic yellowing of skin and eyes, similar to complications seen in viral meningitis and other severe viral infections.
Q3: What are the three phases of yellow fever progression?
Yellow fever progresses through three distinct stages. The febrile phase includes fever, myalgia, and headache. This may be followed by a brief remission where symptoms temporarily improve. In severe cases, the toxic phase develops, characterized by hemorrhage, jaundice, renal dysfunction, and potentially multi-organ failure.
Q4: Why does yellow fever cause jaundice?
Jaundice results from hepatocyte destruction that disrupts bilirubin metabolism. When the liver cannot process bilirubin normally, it accumulates in the blood and tissues, causing the characteristic yellowing of skin and eyes. This buildup occurs because viral infection and immune-mediated damage prevent proper hepatic function.
Q5: How does the immune response contribute to yellow fever tissue damage?
Kupffer cells, the liver's resident macrophages, worsen hepatocellular damage by releasing proinflammatory cytokines during infection. This immune-mediated injury intensifies tissue destruction beyond direct viral effects. The inflammatory response, while attempting to control the virus, paradoxically causes significant organ damage during severe yellow fever.
Q6: What role do lymph nodes play in yellow fever infection?
After the virus infects local immune cells in the skin, these cells migrate to nearby lymph nodes where viral replication significantly increases. This amplification in lymph nodes leads to viremia, allowing the virus to enter the bloodstream and spread systemically to vital organs including the liver.
Q7: How effective is the yellow fever vaccine for prevention?
A single dose of the live-attenuated yellow fever vaccine provides long-lasting immunity and is the cornerstone of prevention. The vaccine triggers strong neutralizing antibody responses that protect against future infections. Broad vaccination coverage combined with vector control represents the essential public health strategy for reducing transmission in endemic regions.