登革热第二次感染为什么可能更严重？
Why can a second dengue infection be more severe than the first?
登革病毒有四种血清型，感染一种后只对该型产生持久免疫。当再次感染不同血清型时，之前产生的抗体不能中和新病毒，却能与它结合并通过巨噬细胞表面的Fc受体带病毒进入细胞，这种“抗体依赖增强”现象使病毒载量升高。结果更容易出现血浆渗漏、血小板下降和休克，即重症登革热。出现持续腹痛、反复呕吐、牙龈或消化道出血、极度嗜睡等警示征象时须立即就医。
Dengue virus has four serotypes, and infection with one gives lasting immunity only to that serotype. On infection with a different serotype, the earlier antibodies cannot neutralize the new virus but can bind it and ferry it into cells through Fc receptors on macrophages - antibody-dependent enhancement - which raises the viral load. That makes plasma leakage, falling platelets and shock more likely, the picture of severe dengue. Warning signs such as persistent abdominal pain, repeated vomiting, bleeding gums or gut, and extreme drowsiness call for immediate medical care.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
葛均波 等主编,《内科学》第9版,人民卫生出版社,2018
Ge Junbo et al. eds., Internal Medicine, 9th ed., PMPH, 2018
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787117265416（豆瓣书目条目: 内科学）
#登革热 #血清型 #抗体依赖增强 #重症登革
HIV是怎样一步步破坏免疫系统的？
How does HIV progressively destroy the immune system?
HIV是一种逆转录病毒，通过表面糖蛋白与CD4分子及CCR5等辅助受体结合，专门感染CD4阳性辅助性T细胞并把自身基因整合进宿主基因组。持续复制使CD4细胞被不断破坏，免疫协调能力下降，当CD4计数降到很低时便出现机会性感染和特定肿瘤，进入艾滋病期。规范的抗病毒治疗可把病毒抑制到检测不到的水平，既能让免疫功能恢复，也能有效阻断传播（“检测不到即不具传染性”）。
HIV is a retrovirus whose surface glycoprotein binds CD4 plus co-receptors such as CCR5, so it specifically infects CD4-positive helper T cells and integrates its genes into the host genome. Continuous replication steadily destroys CD4 cells and dismantles immune coordination; once the CD4 count falls very low, opportunistic infections and specific cancers appear, defining AIDS. Consistent antiretroviral therapy suppresses the virus to undetectable levels, restoring immune function and effectively preventing transmission - the principle of “undetectable equals untransmittable”.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Harrison's Principles of Internal Medicine 第20版,McGraw-Hill,2018
J. Loscalzo et al., Harrison's Principles of Internal Medicine, 20th ed., McGraw-Hill, 2018
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY ISBN 标识 9781259644047（按标识回读: Harrison's prin
#HIV #CD4细胞 #抗病毒治疗 #病毒抑制
麻疹为什么是传染性最强的病毒之一？
Why is measles one of the most contagious viruses known?
麻疹通过空气中的飞沫核传播，病毒在患者离开后仍可在空气和物体表面存活约两小时，其基本传染数R0高达12～18，意味着一个病人平均可传染十几个易感者。没有免疫力的密切接触者约九成会被感染，并可能出现肺炎、中耳炎和脑炎等并发症，感染还会“抹除”部分既有免疫记忆。两剂麻疹疫苗保护率约97%，人群接种率需维持在95%以上才能阻断传播。
Measles spreads through airborne droplet nuclei, and the virus can linger in the air and on surfaces for about two hours after the patient has left; its basic reproduction number R0 of 12-18 means one case infects a dozen or more susceptible people on average. Around 90% of non-immune close contacts become infected, complications include pneumonia, otitis media and encephalitis, and the infection can even erase part of the immune memory built up earlier. Two doses of measles vaccine are about 97% effective, and coverage must stay above 95% to interrupt transmission.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
葛均波 等主编,《内科学》第9版,人民卫生出版社,2018
Ge Junbo et al. eds., Internal Medicine, 9th ed., PMPH, 2018
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787117265416（豆瓣书目条目: 内科学）
#麻疹 #空气传播 #R0 #疫苗接种率
狂犬病为什么一旦出现症状几乎无法救治？
Why is rabies almost always fatal once symptoms appear?
狂犬病毒具有嗜神经性，它从伤口进入后沿周围神经缓慢上行至中枢神经系统，这段潜伏期通常为数周到数月，期间免疫系统难以接触到病毒。一旦病毒到达脑部引起脑炎，出现恐水、躁狂或麻痹等症状，病死率接近100%。但在发病前进行暴露后预防非常有效：立即用肥皂和流水冲洗伤口至少15分钟，尽快接种狂犬疫苗，按暴露级别加用狂犬病免疫球蛋白。
Rabies virus is neurotropic: after entering a wound it travels slowly up peripheral nerves to the central nervous system, an incubation period usually of weeks to months during which the immune system barely encounters it. Once the virus reaches the brain and causes encephalitis, with hydrophobia, agitation or paralysis, the case fatality rate approaches 100%. Post-exposure prophylaxis before symptoms is highly effective, however: wash the wound with soap and running water for at least 15 minutes, get the rabies vaccine as soon as possible, and add rabies immunoglobulin according to the exposure category.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
葛均波 等主编,《内科学》第9版,人民卫生出版社,2018
Ge Junbo et al. eds., Internal Medicine, 9th ed., PMPH, 2018
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787117265416（豆瓣书目条目: 内科学）
#狂犬病 #嗜神经病毒 #暴露后预防 #伤口冲洗
为什么免洗酒精手消液对诺如病毒效果不佳？
Why is alcohol hand sanitizer poor against norovirus?
酒精主要通过破坏病毒的脂质包膜起作用，而诺如病毒是无包膜病毒，外层是坚固的蛋白质衣壳，对酒精抵抗力强。加上它感染剂量极低（十几到上百个病毒颗粒即可致病），环境中还能存活数天，所以酒精擦手远远不够。正确做法是用肥皂和流水认真搓洗至少20秒，被污染的表面用含氯消毒剂处理，患者症状消失后48小时内不要为他人备餐。
Alcohol works mainly by disrupting a virus's lipid envelope, but norovirus is non-enveloped, protected by a tough protein capsid that resists alcohol. Add its extremely low infectious dose - as few as tens to hundreds of particles - and its ability to survive days on surfaces, and alcohol rub is simply not enough. The right approach is scrubbing with soap and running water for at least 20 seconds, disinfecting contaminated surfaces with a chlorine-based product, and not preparing food for others until 48 hours after symptoms stop.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
Harrison's Principles of Internal Medicine 第20版,McGraw-Hill,2018
J. Loscalzo et al., Harrison's Principles of Internal Medicine, 20th ed., McGraw-Hill, 2018
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY ISBN 标识 9781259644047（按标识回读: Harrison's prin
#诺如病毒 #无包膜病毒 #洗手 #含氯消毒
破伤风为什么多发生在又深又脏的伤口？
Why does tetanus typically follow deep, dirty wounds?
破伤风由土壤和粪便中广泛存在的破伤风梭菌芽孢引起，这种细菌是严格厌氧菌。深而窄的刺伤、锈钉扎伤或有坏死组织的伤口内部缺氧，正好让芽孢萌发并释放破伤风毒素。毒素沿神经上行，阻断甘氨酸和GABA等抑制性神经递质释放，导致肌肉持续痉挛、张口困难和危及生命的呼吸肌痉挛。预防靠按程序接种破伤风疫苗、及时彻底清创，必要时按医生评估追加疫苗或抗毒素。
Tetanus is caused by spores of Clostridium tetani, common in soil and faeces, and this bacterium is a strict anaerobe. Deep narrow puncture wounds, injuries from rusty nails and wounds containing dead tissue are low in oxygen inside, exactly the conditions in which spores germinate and release tetanus toxin. The toxin travels up nerves and blocks release of the inhibitory neurotransmitters glycine and GABA, causing sustained muscle spasm, lockjaw and life-threatening spasm of the respiratory muscles. Prevention rests on completing tetanus vaccination and thorough early wound cleaning, with a booster or antitoxin if a clinician judges it necessary.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
葛均波 等主编,《内科学》第9版,人民卫生出版社,2018
Ge Junbo et al. eds., Internal Medicine, 9th ed., PMPH, 2018
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787117265416（豆瓣书目条目: 内科学）
#破伤风 #厌氧菌 #芽孢 #破伤风疫苗