巢氏云∶凡瘟毒病新瘥，脾胃尚虚，谷气未复，若作劳妄动伤力，并食猪、羊、鸡、犬、鱼
脍、炙爆、肥腻、生果、面食，硬涩难消之物，停积肠胃，膈闷腹胀便秘，或大吐大下，
重复发热病作，不可救也。
评热论篇帝曰∶有病温者，汗出辄复热，而脉躁疾，不为汗衰，狂言不能食，病名
为何？岐伯对曰∶病名阴阳交，交者死，不治。（此阴阳交错而血气不循，乱经妄走，而
热所以不息也，故死。）
阴阳易病者，是男子妇人瘟病新瘥，未平复而相交合，因而病复者，名为阴阳易也。男子
病新瘥未平复，而妇人与之交接得病者，名阳易；妇人病新瘥未平复，男子与之交接得病
者，名阴易。若二男二女并不相易，所以呼为易者，阴阳相感动，其毒度着与人，如换易也。
其证身热头重，四肢拘急，小腹 痛者，即死。其病
势缓者，违岁月亦死。
太阳脉大，阳明脉弦长，少阳脉弦数，太阴脉弦细，少阴脉沉，厥阴脉微缓。脉阳濡弱
阴弦紧，更遇温气，变为瘟疫。病瘟而脉洪大者，可治。脉洪而数者，危。两寸浮大按之
无力者，宜补。兼表大热而脉沉涩细小，足冷者，不治。瘟病四五日，体热腹满而吐，脉来
细而强，十二日死。瘟病二三日，头痛腹满，饮食如故，脉直而疾，八日死。瘟病八九日，
头身不痛，目不赤，色不变而反利，脉不牒牒按之不鼓手，时大，心下坚，十七日死。瘟病
汗不出，出不至足者，死。厥逆，汗自出，脉坚强急者生，虚软者死。瘟病下利，腹中痛甚
者死。
巢元方说：凡是瘟毒病刚刚痊愈，脾胃功能仍然虚弱，饮食水谷之气尚未恢复，如果从事劳累、妄动用力，以及食用猪、羊、鸡、狗肉、生鱼片、烤肉、油炸食品、肥腻食物、生冷水果、面食等坚硬涩滞难以消化的食物，导致食物停滞积聚在肠胃中，出现胸膈痞闷、腹部胀满、大便秘结，或者发生剧烈呕吐或腹泻，再次发热且病情复发，就无法救治了。
《评热论篇》中黄帝问道：有一种温病，患者出汗后随即又发热，脉搏躁动疾速，不因出汗而减弱，伴有胡言乱语、不能进食，这种病叫什么名字？岐伯回答说：这种病名叫“阴阳交”，阴阳交错的病证属于死证，无法治疗。（这是因为阴阳交错，气血运行失常，经脉紊乱妄行，所以热势不退，因此死亡。）
所谓“阴阳易”病，是指男子或女子患瘟病刚刚痊愈，身体尚未完全康复时进行房事结合，因而导致疾病复发，这种病称为“阴阳易”。男子患病刚愈尚未康复，与女子发生性关系而致女子得病的，称为“阳易”；女子患病刚愈尚未康复，与男子发生性关系而致男子得病的，称为“阴易”。如果是两个男子或两个女子之间并不互相传染，之所以称为“易”，是因为阴阳相互感应，将病邪毒气转移附着于对方身上，如同更换替换一样。其症状表现为身体发热、头部沉重、四肢拘挛紧急、小腹痛的，即为死证。如果病势较缓的，拖延数月也会死亡。
太阳经的脉象宏大，阳明经的脉象弦长，少阳经的脉象弦数，太阴经的脉象弦细，少阴经的脉象沉伏，厥阴经的脉象微缓。如果脉象表现为阳部濡弱、阴部弦紧，再遇到温热之气侵袭，就会转变为瘟疫。患瘟病而脉象洪大的，可以治疗；脉象洪大而数的，情况危急。两手寸口脉浮大但按之无力的，适宜用补法。兼有表证大热但脉象沉涩细小、足部发冷的，无法治疗。患瘟病四五日，身体发热、腹部胀满且呕吐，脉象来势细而强劲，十二日会死亡。患瘟病二三日，头痛、腹部胀满，但饮食如常，脉象直而疾速，八日会死亡。患瘟病八九日，头身不痛，眼睛不红，面色没有变化反而出现下利（腹泻），脉象不连续跳动、按之无力鼓指，时而变大，心下部坚硬，十七日会死亡。患瘟病不出汗，或者出汗不到足部的，为死证。出现四肢厥逆，自然出汗，脉象坚强急迫的为顺证可生，脉象虚软无力的为逆证必死。患瘟病出现下利，腹部疼痛剧烈的，为死证。
Chao Yuanfang stated: Whenever a patient has just recovered from a pestilential toxic disease, the Spleen and Stomach remain deficient, and the Qi of grain and food has not yet recovered. If one engages in labor, reckless movement, or strains the body, and consumes pork, mutton, chicken, dog meat, raw fish slices, roasted meats, fried foods, fatty and greasy items, raw fruits, wheat-based foods, and other hard, astringent, and difficult-to-digest substances, these will stagnate and accumulate in the intestines and stomach. This leads to chest and diaphragm oppression, abdominal distension, and constipation, or severe vomiting and purging. If fever recurs and the disease relapses, it is incurable.
In the "Ping Re Lun" (Evaluation of Heat Treatise), the Yellow Emperor asked: There is a type of warm disease where the patient sweats but immediately becomes feverish again, the pulse is rapid and restless, does not diminish with sweating, and is accompanied by delirious speech and inability to eat. What is the name of this disease? Qibo replied: The disease is named Yin-Yang Jiao (Yin-Yang Intersection). Diseases characterized by intersection are fatal and untreatable. (This refers to the disorder of Yin and Yang, where Qi and Blood do not follow their proper courses, meridians become chaotic and erratic, causing the heat to persist incessantly, hence death.)
The disease known as Yin-Yang Yi (Yin-Yang Exchange) occurs when a man or woman, having just recovered from a pestilential disease but not yet fully restored, engages in sexual intercourse, thereby causing the disease to recur. This condition is called Yin-Yang Yi. When a man who has just recovered from illness but is not yet stable engages in coitus with a woman, causing her to fall ill, it is called Yang Yi; when a woman who has just recovered but is not yet stable engages in coitus with a man, causing him to fall ill, it is called Yin Yi. If two men or two women do not transmit the disease to each other, the term "Exchange" is used because Yin and Yang mutually influence each other, transferring the pathogenic toxin to the other person, akin to swapping or exchanging. Symptoms include fever, heavy head, stiffness and cramping of the four limbs, and lower abdominal pain; if these occur, it is a death case. If the disease progression is slow, death may still occur after months.
The Taiyang (Greater Yang) pulse is large; the Yangming (Yang Brightness) pulse is string-like and long; the Shaoyang (Lesser Yang) pulse is string-like and rapid; the Taiyin (Greater Yin) pulse is string-like and fine; the Shaoyin (Lesser Yin) pulse is deep; the Jueyin (Terminal Yin) pulse is slightly moderate. If the pulse shows deficiency and weakness in the Yang position and string-tightness in the Yin position, and is further exposed to warm Qi, it transforms into a plague/epidemic. In pestilential diseases, if the pulse is Hongda (Surging and Large), it is treatable; if the pulse is Hong (Surging) and Shu (Rapid), it is critical. If both Cun (Inch) positions are floating and large but weak upon pressure, tonification is indicated. If there is exterior excess heat combined with a Chen Se Xiao Xi (Deep, Choppy, Fine, and Small) pulse and cold feet, it is untreatable. In pestilential disease lasting four to five days, with body heat, abdominal fullness, and vomiting, if the pulse comes forth thin but strong, death occurs on the twelfth day. In pestilential disease lasting two to three days, with headache and abdominal fullness but normal diet, if the pulse is straight and rapid, death occurs on the eighth day. In pestilential disease lasting eight to nine days, with no head or body pain, red eyes, or color changes, but instead presenting with diarrhea, if the pulse is irregular (Die Die), non-pulsating upon pressure, occasionally large, and the epigastrium is firm, death occurs on the seventeenth day. In pestilential disease, if sweat does not appear, or if sweating does not reach the feet, it is a death case. In cases of Jue Ni (Cold Extremities), if spontaneous sweating occurs and the pulse is strong, rigid, and urgent, life is possible; if the pulse is deficient and soft, death ensues. In pestilential disease with diarrhea, if abdominal pain is severe, it is a death case.